JP2016072309A - Lithium ion capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium ion capacitor which is superior in endurance against short and chemical and physical stability while having a separator composed of a thin film, and which enables the realization of a low internal resistance, and is superior in heat resistance, and long-term stability.SOLUTION: A lithium ion capacitor comprises: an electrode laminate arranged by laminating a negative electrode body including a negative electrode active material layer including a carbon material as a negative electrode active material, a separator, and a positive electrode body including a positive electrode active material layer including a positive electrode active material consisting of a carbon material or carbon compound material; a nonaqueous electrolytic solution including a lithium ion-containing electrolyte; and an outer sheath in which the electrode laminate and the nonaqueous electrolytic solution are enclosed. The separator is constituted by no more than three layers including at least one cellulose fine fiber layer including 70 wt% or more of regenerated cellulose fine fiber. The lithium ion capacitor satisfies the following conditions: the specific surface area equivalent fiber diameter of fibers making up the cellulose fine fiber layer is 0.20-0.45 μm; the aeration resistance is 5-40 s/100 ml; and the film thickness is 8-22 μm.SELECTED DRAWING: None

Description

  The present invention relates to a lithium ion capacitor using a separator having a fine network structure formed by cellulose fine fibers.

  Storage devices mainly include battery-type devices such as nickel-hydrogen batteries and lithium secondary ion batteries, and capacitor-type devices such as aluminum electrolytic capacitors, electric double layer capacitors, and lithium ion capacitors. Conventionally, the capacitance of a capacitor-based device has been a relatively small capacitance on the order of several pF (picofarad) to several mF (millifarad). Capacitance capacitors have emerged, and in particular, lithium ion capacitors are reaching a level comparable to battery-based devices from the viewpoint of energy density. As a result, the lithium-ion capacitor is not equipped with a conventional battery that (1) it has no electrochemical reaction and is excellent in repeated resistance, and (2) it has a high output density and can output stored electricity all at once. Taking advantage of the unique characteristics of the capacitor, it is attracting attention as an onboard storage device for next-generation vehicles such as hybrid vehicles and fuel cell vehicles.

  As a matter of course, such an electricity storage device is appropriately selected according to its use, and has been used in a field suitable for each device. Among them, for example, many researchers have entered the development of the above-mentioned power storage device for next-generation automobiles in that a large new market can be expected. The development of fuel cells in fuel cell vehicles is the most prominent field. Regarding next-generation automotive energy storage devices, new performance (for example, high-temperature resistance as a usage environment, higher energy density, etc.) that was not required in conventional applications from the viewpoint of energy storage devices mounted on automobiles. There are many cases where this is necessary, and as a result, improvements at the member level that constitutes the electricity storage device are also being actively carried out.

Speaking of separators, which are one of the main components in many electricity storage devices, the required performance varies naturally depending on the type of electricity storage device. (1) Long-term performance maintenance in the device usage environment (for example, high temperature under charging environment, long-term stability), (2) limited space In particular, the required performance of forming an electricity storage device with a high volumetric energy density that achieves higher capacity without increasing the volume (or lighter and smaller with the same performance) is required.
The above required physical properties of the separator are related to the structural features of the separator as follows. In the low internal resistance separator that has air permeability while having as fine a hole as possible and contributes to the reduction of internal resistance, (1), the separator is essentially made of a heat resistant material, In order to solve the problem (2), it is necessary to be overwhelmingly thinner than conventional separator films.

  In order to solve these problems, many inventions have been made with respect to a cellulose-based separator having excellent surface characteristics in terms of impregnation with respect to many electrolytic solutions. For example, in the following Patent Document 1, a technique using a separator using a beating raw material of solvent-spun cellulose fiber that can be beaten as a raw material in a range of 60 to 100% by weight is reported in an electric double layer capacitor. Since the beating raw material of solvent-spun cellulose fiber is used as the separator raw material, the separator has a very dense structure due to the fibrils obtained by beating, and has a high density to improve the short-circuit defect rate. In order to improve internal resistance, it is disclosed that a separator maintaining a through hole as a path through which ions pass can be obtained. On the other hand, since thick fibers remain, the thickness of the separator obtained is only an example up to 25 μm, and it is stated that further thinning is difficult, and does not satisfy the high efficiency of power storage. .

  Moreover, in the following patent document 2 and patent document 3, the separator for electrical storage devices using the cellulose fiber whose maximum fiber diameter is 1000 nm or less and whose crystallinity calculated | required by solid NMR method is 60% or more is provided. It has been reported. These technologies form a separator for an electricity storage device using fine cellulose having a number average fiber diameter of 200 nm or less from the viewpoint of easily creating a microporous structure. Although it is a technology that expresses low internal resistance by making the cellulose fiber diameter very small and forming a microporous structure, in the electricity storage device using this separator, the fibers are too thin and the surface area is large. It cannot be said that it has sufficient performance in terms of resistance to the redox reaction proceeding around the separator in contact with the electrode, that is, durability. Therefore, it does not satisfy all the required characteristics as a separator as required in automotive applications, and the description and effects of the structural requirements for solving both the above problems (1) and (2). In that respect, the invention remained unfinished. That is, at present, a technology that can provide a separator that satisfies all of the two problems described above in a realistic manner has not yet been established.

JP 2000-3834 A Japanese Patent No. 4628764 International Publication No. 2006/004012 Pamphlet

  In view of the above situation, the problem to be solved by the present invention is that the separator is a thin film, but has excellent short circuit resistance and chemical / physical stability, realizes low internal resistance as a device, and further has heat resistance. It is to provide a lithium ion capacitor having excellent long-term stability.

  As a result of intensive studies to solve the above-mentioned problems and repeated experiments, the inventors of the present invention are microporous and high-porosity fine cellulose sheets made of fine cellulose fibers, which have a specific surface area of regenerated cellulose fine fibers. It has been found that the above-mentioned problems can be solved by designing an equivalent fiber diameter of 0.20 μm to 0.45 μm, an air resistance of 5 s / 100 ml to 40 s / 100 ml, and a film thickness of 8 μm to 22 μm. The present invention has been completed.

That is, the present invention is as follows.
[1] A negative electrode body in which a negative electrode active material layer containing a carbon material as a negative electrode active material is disposed on a negative electrode current collector;
A positive electrode body in which a positive electrode active material layer including a positive electrode active material made of either a carbon material or a carbon compound material is disposed on a positive electrode current collector;
A non-aqueous electrolyte containing a lithium ion-containing electrolyte;
A lithium ion capacitor that is housed in an exterior body,
The separator is composed of a single layer containing at least one cellulose fine fiber layer containing regenerated cellulose fine fibers at 70% by weight or more, or a plurality of layers of 3 layers or less, and the following requirements:
(1) The specific surface area equivalent fiber diameter of the fibers constituting the cellulose fine fiber layer is 0.20 μm or more and 0.45 μm or less;
(2) Air permeability resistance is 5 s / 100 ml or more and 40 s / 100 ml or less; and (3) Film thickness is 8 μm or more and 22 μm or less;
The lithium ion capacitor characterized by being a separator satisfying the following.

[2] The lithium ion capacitor according to [1], wherein the basis weight of the cellulose fine fiber layer is 4 g / m ² or more and 13 g / m ² or less.

  [3] The lithium ion capacitor according to [1] or [2], wherein the regenerated cellulose fine fiber has a specific surface area equivalent fiber diameter of 0.20 μm or more and 0.45 μm or less.

  [4] The lithium ion capacitor according to any one of [1] to [3], wherein the cellulose fine fiber layer contains natural cellulose fine fibers at less than 30% by weight.

  [5] The lithium ion capacitor according to any one of [1] to [4], wherein the cellulose fine fiber layer includes natural cellulose fine fibers that are fine fibers having a CSF of 300 ml ↑ or more in an amount of less than 30% by weight.

  [6] The lithium ion capacitor according to any one of [1] to [3], wherein the cellulose fine fiber layer contains fine fibers made of an organic polymer other than cellulose at less than 30% by weight.

  [7] The lithium ion capacitor according to any one of [1] to [6], wherein the cellulose fine fiber layer contains a reactive crosslinking agent in an amount of 10% by weight or less.

[8] one layer of the multilayer structure of 3 layers or less, comprising a substrate layer is a basis weight 3 g / ^{m 2} or more 15 g / ^{m 2} or less of the nonwoven fabric or paper, the [1] to [7] according to any one Lithium ion capacitor.

  [9] The lithium ion capacitor according to any one of [1] to [8], wherein an insulating porous film is formed on one side or both sides of the separator.

[10] The lithium ion capacitor according to [9], wherein the insulating porous film includes an inorganic filler and a resin binder, and has a basis weight of 2 g / m ² or more and 10 g / m ² or less.

  [11] The negative electrode active material is a composite porous material in which the surface of activated carbon is coated with a carbon material, and the amount of mesopores derived from pores having a diameter of 20 to 500 mm calculated by the BJH method is Vm1 ( cc / g), when the amount of micropores derived from pores having a diameter of less than 20 mm calculated by the MP method is Vm2 (cc / g), 0.010 ≦ Vm1 ≦ 0.250, 0.001 ≦ Vm2 ≦ 0 200 and 1.5 ≦ Vm1 / Vm2 ≦ 20.0, the lithium ion capacitor according to any one of [1] to [10].

  [12] The negative electrode active material is a composite porous material in which the surface of activated carbon is coated with a carbonaceous material, and the unit mass of the composite porous material is not less than 1,050 mAh / g and not more than 2,050 mAh / g. Lithium ions are pre-doped, the mass ratio of the carbonaceous material to the activated carbon is 10% or more and 60% or less, and the thickness of the negative electrode active material layer is 20 μm or more and 45 μm or less per side, The lithium ion capacitor according to any one of [1] to [10].

[13] The positive electrode active material is derived from V1 (cc / g) mesopore amount derived from pores having a diameter of 20 to 500 mm calculated by the BJH method, and from pores having a diameter of less than 20 mm calculated by the MP method. When the amount of micropores is V2 (cc / g), 0.3 <V1 ≦ 0.8 and 0.5 ≦ V2 ≦ 1.0 are satisfied, and the specific surface area measured by the BET method is 1, The lithium ion capacitor according to any one of [1] to [12], wherein the lithium ion capacitor is activated carbon that exhibits 500 m ² / g or more and 3000 m ² / g or less.

[14] The positive electrode active material has a mesopore volume V1 (cc / g) derived from pores having a diameter of 20 mm or more and 500 mm or less calculated by the BJH method satisfying 0.8 <V1 ≦ 2.5, and by the MP method. The calculated micropore amount V2 (cc / g) derived from pores having a diameter of less than 20 mm satisfies 0.8 <V2 ≦ 3.0, and the specific surface area measured by the BET method is 3,000 m ² / g. The lithium ion capacitor according to any one of the above [1] to [12], which is activated carbon exhibiting 4,000 m ² / g or less.

  Although the separator of the present invention is a thin film, it has excellent short-circuit resistance, heat resistance, and chemical / physical stability. A lithium ion capacitor using the separator has excellent electrical characteristics (low internal resistance, small leakage). Current value etc.) and long-term stability can be realized.

Hereinafter, embodiments of the present invention will be described in detail.
The separator used in the lithium ion capacitor of the present embodiment is a separator for an electricity storage device composed of a single layer including at least one cellulose fine fiber layer containing 70% by weight or more of regenerated cellulose fine fibers or a plurality of layers of 3 layers or less. ,below:
(1) The specific surface area equivalent fiber diameter of the fibers constituting the cellulose fine fiber layer is 0.20 μm or more and 0.45 μm or less;
(2) Air permeability resistance is 5 s / 100 ml or more and 40 s / 100 ml or less; and (3) Film thickness is 8 μm or more and 22 μm or less;
It is a separator characterized by these.

When a reduction in internal resistance is pursued in an electricity storage device, ideally there is no separator, that is, a state where the space where the separator exists is filled with an electrolyte is desired. This is because the constituent material of the separator, which is originally a non-conductive solid, has an extremely high electric resistance with respect to the electrolytic solution. However, this causes a problem with short-circuiting due to contact between the positive and negative electrodes, and therefore a separator having as high a porosity as possible, that is, having as much space as can be replaced with the electrolyte is required.
As the types of separators, non-woven separators and microporous membrane (generally porous membranes) separators can be considered, but the present inventors have the same degree of through-hole size. It was found that a cellulose-based non-woven fabric is desirable when the porosity of is assumed. The reason why cellulose is desirable as a material is that it has amphiphilic surface characteristics (for example, H. Ono et al., Trans. Mat. Res. Soc. Jpn., 26, 569-572 (2001)) It is because the wettability with respect to the water-system electrolyte solution or organic-system electrolyte solution used with many electrical storage devices is very favorable. In fact, cellulose nonwoven fabric (paper) is used as a separator for aluminum electrolytic capacitors and lead-acid batteries. In addition, the reason why the nonwoven fabric film is superior to the microporous film is that the former is a closed pore (one side of the hole is connected to the through hole) in addition to the open pore (the hole having the through hole or both sides of the hole being connected to the through hole). In the latter case, the structure consists of almost only open pores, and when the surface wettability is good, it is possible to create a state where most of the pores are occupied by the electrolyte. is there. In a microporous membrane having closed pores, pores are present even when impregnated with an electrolytic solution for various reasons such as surface tension, particularly when the pore diameter is small. Basically, a gas phase such as air has a higher resistance value than the electrolytic solution, so the presence of closed pores inhibits the reduction of internal resistance.
Further measures to reduce the internal resistance are to reduce the thickness of the separator, but there is a limit to reducing the thickness of the non-woven fabric with normal fibers (thin fibers having a fiber diameter of several μm or more). is there. This is because if the separator is made of a relatively thick fiber and is thin and has a high porosity, the diameter of the through-hole becomes large, causing a problem in short-circuit resistance. In other words, to provide a thin non-woven membrane that contributes to a reduction in internal resistance with a high porosity and a small through-hole diameter, it is essential to use cellulose fibers having a fine fiber diameter.

Hereinafter, the conditions of the separator used for the lithium ion capacitor of this embodiment will be described in detail.
First, the fine cellulose fiber which comprises the separator of this embodiment is demonstrated.
In the present specification, regenerated cellulose is a substance obtained by regenerating natural cellulose by dissolving or crystal swelling (mercelization) treatment, and the lattice spacing of 0.73 nm, 0.44 nm and 0. A β1,4-bonded glucan (glucose polymer) having a molecular arrangement that gives a crystal diffraction pattern (cellulose type II crystal) with a diffraction angle corresponding to 40 nm as the apex, such as rayon, cupra, tencel, etc. Regenerated cellulose fiber is meant. Among these, from the viewpoint of ease of miniaturization, it is preferable to use fine fibers made from cupra or tencel having a high molecular orientation in the fiber axis direction.

The maximum fiber thickness of the regenerated cellulose fine fiber is preferably 3 μm or less, more preferably 2.5 μm or less, and further preferably 2 μm or less. Here, the maximum fiber thickness of 3 μm or less means that no fiber exceeding 3 μm fiber diameter can be confirmed on the image in an electron microscope (SEM) of a cellulose nonwoven fabric measured under the following conditions. .
A surface SEM image of the separator was collected at a magnification equivalent to 10,000 times, and the fiber diameter of any entangled fiber contained in this image was 3 μm or less, and similarly, any part of the cast surface was subjected to the same conditions. When a fiber exceeding a fiber diameter of 3 μm cannot be confirmed in the same manner for a total of 100 or more fibers, the maximum fiber diameter is defined as 3 μm or less. However, if it can be clearly confirmed that several fine fibers are bundled in the image to have a fiber diameter of 3 μm or more, it is not considered as a fiber having a fiber diameter of 3 μm or more. When the maximum fiber thickness exceeds 3 μm, it is difficult to ensure uniformity such as pore diameter in the production of a thin film separator, which is not preferable.

As the separator of this embodiment, the specific surface area equivalent fiber diameter of the cellulose fine fiber layer containing 70% by weight or more of regenerated cellulose is preferably 0.45 μm or less, more preferably 0.43 μm or less, and further preferably 0.40 μm or less. is there. Here, the specific surface area equivalent fiber diameter will be described. The specific surface area is first evaluated using the BET method by nitrogen adsorption, and the fibers constituting the separator are virtually in an ideal state in which no fusion between the fibers occurs with respect to the specific surface area, and the cellulose density Is a cylindrical model in which the surface is constituted by fibers that are cylinders of which d is g (cm / cm ³ ) and L / D (L: fiber length, D: fiber diameter (both units: μm)) is infinite Depending on the specific surface area and fiber diameter:
Specific surface area = 4 / (dD) (m ² / g)
Induced. The specific surface area by the BET method is substituted as the specific surface area of the above formula, and the numerical value converted to the fiber diameter D by substituting d = 1.50 g / cm ³ as the cellulose density is defined as the specific surface area equivalent fiber diameter. Here, the specific surface area measurement by the BET method is performed by measuring the adsorption amount of nitrogen gas at the boiling point of liquid nitrogen with respect to about 0.2 g of sample with a specific surface area / pore distribution measuring device (manufactured by Beckman Coulter). Then, the specific surface area was calculated.

  The separator of the present embodiment can suitably provide a separator having a uniform thickness distribution by selecting the fiber diameter corresponding to the specific surface area of the cellulose fine fiber layer containing 70% by weight or more of regenerated cellulose fine fibers in the above range. . When the fiber diameter corresponding to the specific surface area of the cellulose fine fiber layer containing 70% by weight or more of the regenerated cellulose exceeds 0.45 μm, the fiber diameter is too thick, so that the distribution of the microporous structure by the fine fibers described above becomes large, that is, large Since the holes having the hole diameter are scattered, it is not preferable from the viewpoint of pursuing a thin film while maintaining short-circuit resistance.

  The fiber diameter corresponding to the specific surface area of the cellulose fine fiber layer containing 70% by weight or more of regenerated cellulose fine fibers is preferably 0.20 μm or more, more preferably 0.25 μm or more. When the fiber diameter corresponding to the specific surface area of the cellulose fine fiber layer containing 70% by weight or more of regenerated cellulose is less than 0.20 μm, when the device is assembled and charged and discharged for long-term stability evaluation, the fiber diameter is too thin. This is not preferable because it may cause deterioration and increase internal resistance over time or gas generation.

  The separator of the present embodiment has a gas permeability resistance in the range of 5 s / 100 ml to 40 s / 100 ml. Here, the air resistance is a numerical value measured based on the Gurley tester method described in JIS P 8117. The air resistance is preferably in the range of 6 s / 100 ml to 35 s / 100 ml. If the air permeation resistance is lower than 5 s / 100 ml, problems occur in terms of short-circuit resistance and strength, and the function as a separator is not exhibited, which is not preferable. In addition, when it exceeds 40 s / 100 ml, the porosity is remarkably reduced or the pore diameter becomes too small, which is disadvantageous in terms of ion permeability of the electrolytic solution, and acts as an effect of increasing internal resistance. It is not preferable.

The separator of this embodiment can be obtained by processing fine cellulose fibers into a sheet as described above, but it is preferable that the film thickness is substantially 8 μm or more and 22 μm or less due to processing and functional restrictions. . Here, the film thickness is measured by using a surface contact type film thickness meter, for example, a Mitutoyo film thickness meter (Model ID-C112XB) or the like, and cutting a 10.0 cm × 10.0 cm square piece from the separator. The average value of the measured values at five points for a certain position is defined as a film thickness T (μm). Further, from the film thickness T (μm) of a 10.0 cm × 10.0 cm square piece cut out in the measurement of the film thickness and its weight W (g), the following formula:
W0 = 100 × W
Can be used to calculate the basis weight W0 (g / m ² ) of the film.

  The film thickness of the separator of this embodiment is more preferably 9 μm or more and 20 μm or less, and further preferably 9 μm or more and 18 μm or less. When the film thickness is in the above range, a separator having extremely good electrical characteristics (functional aspect) such as low internal resistance and handling property when winding a separator to assemble a device is obtained. If the thickness is less than 8 μm, it is difficult to handle in the device assembling process, which may be inappropriate. On the other hand, if the thickness is larger than 22 μm, a desirable effect such as a reduction in internal resistance may not be expected.

The basis weight of the cellulose fine fiber layer used in the separator of the present embodiment is preferably 4 g / m ² or more and 13 g / m ² or less, more preferably 5 g / m ² or more and 12 g / m ² or less. When the basis weight is less than 4 g / m ^2, it is difficult to handle in the device assembly process and may be inappropriate, which is not preferable from the viewpoint of long-term stability. On the other hand, if the basis weight is larger than 13 g / m ² , it is not possible to reduce the thickness of the film, and a desirable effect such as a low internal resistance cannot be expected due to an increase in the basis weight of the insulator.

  The cellulose fine fiber layer containing 70% by weight or more of the regenerated cellulose fine fiber used in the separator of the present embodiment may further contain less than 30% by weight of natural cellulose fine fiber in addition to the regenerated cellulose fine fiber. By using natural cellulose fine fibers, it is relatively easy to produce fine cellulose fibers having a fiber diameter of less than 0.20 μm from the fineness of microfibrils, which are the structural units, and the finer fiber length / fiber Separator strength can be increased by mixing natural cellulose fine fibers having a large diameter ratio. By containing less than 30% by weight, the strength of the cellulose fine fiber layer is increased, and the separator becomes extremely good in handling when assembling the device. The content of natural cellulose fine fibers is preferably less than 20% by weight.

As for the natural cellulose fine fiber diameter in the cellulose fine fiber layer used for the separator of this embodiment, it is preferable that the maximum fiber thickness is 2 micrometers or less. When the maximum fiber diameter is too large, it may not be preferable from the viewpoint of pursuing a thin film while maintaining short-circuit resistance based on the above-described microporous structure with fine fibers.
Natural cellulose fine fibers whose maximum fiber diameter does not exceed 2 μm include wood pulp obtained from hardwoods or conifers, refined linters, or refined pulps from various plant species (bamboo, hemp fiber, bagasse, kenaf, linter, etc.) In addition to those obtained by highly refining and the like, natural cellulose fine fibers that are aggregates of never-dry and fine fibers such as bacterial cellulose (BC) produced by cellulose-producing bacteria (bacteria) are also included.

  In addition, the cellulose fine fiber layer containing 70% by weight or more of the regenerated cellulose fine fibers used in the separator of this embodiment further contains less than 30% by weight of fine fibers made of an organic polymer other than cellulose in addition to the regenerated cellulose fine fibers. Preferably, it is 25 weight% or less. As the organic polymer, any organic polymer capable of producing fine fibers can be used. For example, aromatic or aliphatic polyester, nylon, polyacrylonitrile, cellulose acetate, polyurethane, polyethylene, polypropylene, polyketone In addition, natural organic polymers other than cellulose, such as aromatic polyamide, polyimide, silk, and wool, can be mentioned, but are not limited thereto. The fine fibers made of the organic polymer are fine fibers obtained by beating organic fibers, or highly fibrillated or miniaturized by a refining process using a high-pressure homogenizer, various fine fibers obtained by electrospinning using various polymers as raw materials, Although the fine fiber etc. which are obtained with a polymer by the melt blown method can be mentioned as a raw material, it is not limited to these. Among these, a microfibrous aramid obtained by refining an aramid fiber, which is a wholly aromatic polyamide, with a high-pressure homogenizer, Tiara (registered trademark) (manufactured by Daicel Chemical Industries) has an average fiber diameter of 0.2 to 0.00. It is 3 μm and has an average fiber length of 500 to 600 μm, and can be suitably used as a fibrous filler in the present embodiment, coupled with high heat resistance and high chemical stability of aramid fibers.

  Next, the manufacturing method of a cellulose fine fiber is described. The refining of the cellulose fiber is preferably performed through a pretreatment step, a beating treatment step, and a refining step for both the regenerated cellulose fiber and the natural cellulose fiber. In particular, when regenerated cellulose fibers are refined, the pretreatment step can be carried out in a water washing step using a surfactant to remove the oil agent, but in the pretreatment step of natural cellulose fibers, It is effective to make the raw material pulp easy to be refined in the subsequent steps by autoclave treatment under an impregnation in water at a temperature of 150 ° C., enzyme treatment, or a combination thereof. These pretreatments not only reduce the load of the micronization process, but also discharge impurity components such as lignin and hemicellulose present on the surface and gaps of the microfibrils that make up the cellulose fibers to the aqueous phase, resulting in a finer process. Since there is also an effect of increasing the α-cellulose purity of the formed fiber, it may be very effective in improving the heat resistance of the fine cellulose fiber nonwoven fabric.

After the beating process, both regenerated cellulose fibers and natural cellulose fibers are produced with the following contents.
In the beating treatment step, the raw material pulp is 0.5 wt% or more and 4 wt% or less, preferably 0.8 wt% or more and 3 wt% or less, more preferably 1.0 wt% or more and 2.5 wt% or less. Disperse in water to a partial concentration and highly promote fibrillation with a beating device such as a beater or disc refiner (double disc refiner). When a disc refiner is used, if the clearance between the discs is set as narrow as possible (for example, 0.1 mm or less) and processing is performed, extremely advanced beating (fibrillation) proceeds. The conditions for the miniaturization treatment can be relaxed and may be effective.

A preferable degree of beating processing is determined as follows. In the study by the inventors of the present application, the CSF value (indicating the degree of cellulose beating. Evaluated by the Canadian standard freeness test method for pulp as defined in JIS P 8121) decreases with time as the beating process is performed. In order to prepare the fine cellulose fiber that is the raw material of the nonwoven fabric structure of the present embodiment, once it was close to zero and then continued to be further beaten, it was confirmed that the pre-treatment As described above, it was found that it is preferable that the beating process is further continued until the CSF value is increased after the CSF value is once close to zero. In the present specification, the CSF value in the process of decreasing the CSF value from unbeaten is expressed as *** ml ↓, and the CSF value in a tendency to increase after becoming zero is expressed as *** ml ↑. In the beating process, regardless of whether the cellulose is regenerated cellulose or natural cellulose, the beating step preferably has a beating degree higher than at least zero and more preferably higher than CSF 30 ml ↑. In the aqueous dispersion prepared to such a beating degree, fibrillation proceeds to a high degree. In particular, with regard to regenerated cellulose, the fiber diameter corresponding to the specific surface area is 0 by combining the beating and further refinement treatment described later. A fine fiber having a size of 20 μm or more and 0.45 μm or less can be produced. A highly beaten water dispersion with a CSF value of at least zero or subsequently increasing *** ml ↑ increases the homogeneity and reduces the clogging caused by subsequent refinement with a high-pressure homogenizer, etc. There is an efficiency advantage. Further, when producing fine fibers of natural cellulose, it is beaten from CSF 300 ml ↑ as a fine fiber slurry by combining the above-described beating step and further refinement treatment from the viewpoint of reinforcing the strength of the separator. However, it is more preferably CSF 350 ml ↑ or more.
Moreover, when manufacturing the fine fiber of regenerated cellulose, it is beaten rather than CSF100ml ↑ as a fine fiber slurry by combining the said beating process and the further refinement | miniaturization process, and a viewpoint of strength reinforcement of a separator However, it is more preferably CSF 150 ml ↑ or more.

In the production of the fine cellulose fiber, it is preferable to carry out a refining treatment with a high-pressure homogenizer, an ultra-high pressure homogenizer, a grinder or the like following the above-described beating step. In this case, the solid content concentration in the aqueous dispersion is 0.5 wt% or more and 4 wt% or less, preferably 0.8 wt% or more and 3 wt% or less, more preferably 1.0 wt. % By weight to 2.5% by weight. In the case of a solid content concentration in this range, clogging does not occur and an efficient miniaturization process can be achieved.
Examples of the high-pressure homogenizer used include NS type high-pressure homogenizer manufactured by Niro Soabi (Italy), SMT Co., Ltd., Lanier type (R model) pressure-type homogenizer, Sanwa Kikai Co., Ltd. high-pressure type homogenizer, and the like. Any device other than these devices may be used as long as the device performs miniaturization by a mechanism substantially similar to those of these devices. Ultra-high pressure homogenizers mean high-pressure collision type miniaturization machines such as Mizuho Kogyo Co., Ltd. microfluidizer, Yoshida Kikai Kogyo Co., Ltd. Nanomizer, Sugino Machine Ultimate Co., Ltd. Any device other than these devices may be used as long as the device performs miniaturization with a substantially similar mechanism. Examples of the grinder-type miniaturization device include the pure fine mill of Kurita Machinery Co., Ltd. and the stone mill type milling die represented by Masuyuki Sangyo Co., Ltd. Any device other than these may be used as long as the device performs miniaturization by this mechanism.

The fiber diameter of the fine cellulose fiber is determined according to the conditions for refinement using a high-pressure homogenizer (selection of equipment and operating pressure and number of passes) or pre-treatment conditions (for example, autoclave treatment, enzyme treatment, beating treatment). Etc.).
Furthermore, as a natural cellulose fine fiber that can be used in the present invention, a hydroxyl group at the 6-position is oxidized by a cellulose-based fine fiber subjected to chemical treatment of the surface and a TEMPO oxidation catalyst, and a carboxyl group (including an acid type and a salt type). The resulting cellulose-based fine fibers can also be used as the fine cellulose fibers of the present invention. In the former case, by subjecting to various surface chemical treatments depending on the purpose, for example, some or most of the hydroxyl groups present on the surface of the fine cellulose fiber are esterified including acetate ester, nitrate ester, sulfate ester. In addition, etherified products including alkyl ethers typified by methyl ether, carboxy ethers typified by carboxymethyl ether, and cyanoethyl ether can be appropriately prepared and used. Moreover, in the preparation of the latter, that is, the fine cellulose fiber in which the hydroxyl group at the 6-position is oxidized by the TEMPO oxidation catalyst, it is not always necessary to use a high-energy refining device such as a high-pressure homogenizer. A dispersion can be obtained. For example, as described in the literature (A. Isogai et al., Biomacromolecules, 7, 1687-1691 (2006)), 2,2,6,6-tetramethylpiperidinooxy is added to an aqueous dispersion of natural cellulose. By mixing a catalyst called TEMPO such as a radical with an alkyl halide, adding an oxidant such as hypochlorous acid to this, and allowing the reaction to proceed for a certain period of time, after a purification treatment such as water washing, an ordinary mixer By performing the treatment, a dispersion of fine cellulose fibers can be obtained very easily.
In the present invention, two or more kinds of the above-mentioned regenerated cellulose or natural cellulose-based fine fibers of different raw materials, natural cellulose fine fibers having different fibrillation degrees, natural cellulose fine fibers whose surface has been chemically treated, etc. It may be effective to mix the amounts specified in the invention to form a cellulose fine fiber layer.

  Even if the cellulose fine fiber layer used for the separator of the present embodiment contains 10% by weight or less of a reactive crosslinking agent, it may be effective for reinforcing the strength. The reactive crosslinking agent refers to a reactant derived from a polyfunctional isocyanate, and refers to a resin produced by an addition reaction between a polyfunctional isocyanate compound and an active hydrogen-containing compound. By containing 10% by weight or less of the reactive cross-linking agent, the strength of the cellulose fine fiber layer is increased, and the separator becomes extremely good in handling when assembling the device. More preferably, it is 6% by weight or less.

  Examples of the reactive crosslinking agent polyfunctional isocyanate compound that forms the reactive crosslinking agent in the cellulose fine fiber layer used in the separator for an electricity storage device of the present embodiment include, for example, aromatic polyfunctional isocyanates, araliphatic polyhydric isocyanates, and the like. Functional isocyanate, alicyclic polyfunctional isocyanate, aliphatic polyfunctional isocyanate, etc. are mentioned. From the viewpoint of less yellowing, alicyclic polyfunctional isocyanates and aliphatic polyfunctional isocyanates are more preferable. In addition, one type or two or more types of polyfunctional isocyanate compounds may be contained.

Examples of the aromatic polyfunctional isocyanate include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate and a mixture thereof (TDI), diphenylmethane-4,4′-diisocyanate (MDI), and naphthalene-1,5. -Aromatic polyfunctional isocyanates such as diisocyanate, 3,3-dimethyl-4,4-biphenylene diisocyanate, crude TDI, polymethylene polyphenyl diisocyanate, crude MDI, phenylene diisocyanate and xylylene diisocyanate.
Examples of the alicyclic polyfunctional isocyanate include alicyclic polyfunctional isocyanates such as 1,3-cyclopentane diisocyanate, 1,3-cyclopentene diisocyanate, and cyclohexane diisocyanate.
Examples of the aliphatic polyfunctional isocyanate include aliphatic polyfunctional isocyanates such as trimethylene diisocyanate, 1,2-propylene diisocyanate, butylene diisocyanate, pentamethylene diisocyanate, and hexamethylene diisocyanate.
Examples of the active hydrogen-containing compound include a hydroxyl group-containing compound including a monohydric alcohol, a polyhydric alcohol, and phenols, an amino group-containing compound, a thiol group-containing compound, and a carboxyl group-containing compound. Also included are water and carbon dioxide present in the air or in the reaction field. One or more active hydrogen-containing compounds may be contained.

Examples of the monohydric alcohol include alkanols having 1 to 20 carbon atoms (methanol, ethanol, butanol, octanol, decanol, dodecyl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, etc.), and alkenols having 2 to 20 carbon atoms (oleyl alcohol). And linoleyl alcohol) and araliphatic alcohols having 7 to 20 carbon atoms (such as benzyl alcohol and naphthylethanol).
Examples of the polyhydric alcohol include divalent alcohols having 2 to 20 carbon atoms [aliphatic diols (ethylene glycol, propylene glycol, 1,3- or 1,4-butanediol, 1,6-hexanediol, neopentyl glycol). And 1,10-decanediol, etc.), alicyclic diols (cyclohexanediol, cyclohexanedimethanol, etc.) and araliphatic diols {1,4-bis (hydroxyethyl) benzene, etc.}, etc. Trihydric alcohols [aliphatic triols (such as glycerin and trimethylolpropane)] and 4- to 8-valent alcohols having 5 to 20 carbon atoms [aliphatic polyols (pentaerythritol, sorbitol, mannitol, sorbitan, diglycerin and dipentaerythritol) Etc.) and sugars (sucrose, guru) Over scan, mannose, fructose, methyl glucoside and derivatives thereof)], and the like.

Examples of phenols include monovalent phenols (phenol, 1-hydroxynaphthalene, anthrol, 1-hydroxypyrene, etc.) and polyhydric phenols (phloroglucin, pyrogallol, catechol, hydroquinone, bisphenol A, bisphenol F, bisphenol S, 1,3,6,8-tetrahydroxynaphthalene, 1,4,5,8-tetrahydroxyanthracene, a condensate of phenol and formaldehyde (novolak) and polyphenol described in US Pat. No. 3,265,641] and the like It is done.
Examples of the amino group-containing compound include monohydrocarbylamines having 1 to 20 carbon atoms [alkylamine (butylamine and the like), benzylamine and aniline and the like], aliphatic polyamines having 2 to 20 carbon atoms (ethylenediamine, hexamethylenediamine and the like). Diethylenetriamine, etc.), C6-C20 alicyclic polyamines (diaminocyclohexane, dicyclohexylmethanediamine, isophoronediamine, etc.), C2-C20 aromatic polyamines (phenylenediamine, tolylenediamine, diphenylmethanediamine, etc.), carbon Heterocyclic polyamines of 2 to 20 (such as piperazine and N-aminoethylpiperazine), alkanolamines (such as monoethanolamine, diethanolamine and triethanolamine), dicarboxylic acid and excess poly Polyamide polyamine, polyether polyamine, hydrazine (such as hydrazine and monoalkyl hydrazine), dihydrazide (such as succinic acid dihydrazide and terephthalic acid dihydrazide), guanidine (such as butyl guanidine and 1-cyanoguanidine) and dicyandiamide obtained by condensation with amine Is mentioned.

Examples of the thiol group-containing compound include monovalent thiol compounds having 1 to 20 carbon atoms (alkyl thiol such as ethyl thiol, phenyl thiol and benzyl thiol) and polyvalent thiol compounds (ethylene dithiol and 1,6-hexanedithiol). Etc.).
Examples of the carboxyl group-containing compound include monovalent carboxylic acid compounds (alkyl carboxylic acids such as acetic acid, aromatic carboxylic acids such as benzoic acid) and polyvalent carboxylic acid compounds (alkyl dicarboxylic acids such as oxalic acid and malonic acid, and terephthalic acid). Aromatic dicarboxylic acids such as acids) and the like.

The cellulose fine fiber layer used in the separator for an electricity storage device of the present embodiment includes a base material layer that is a nonwoven fabric or paper having a basis weight of 3 g / m ² or more and 15 g / ² or less as one layer having a multilayer structure of 3 layers or less. Also good. Even if the strength of the cellulose fine fiber layer itself of the thin film is insufficient by including a base material layer that is a nonwoven fabric or paper having a basis weight of 3 g / m ² or more and 15 g / ² or less, the base material layer supplements the strength. In addition, it is a separator that has extremely good handleability when assembling a device while maintaining the function as a separator for an electricity storage device (low internal resistance and the like).

  Examples of the base material layer used in the electricity storage device separator of the present embodiment include polyamide fibers such as 6-nylon and 6,6-nylon, polyester fibers such as polyethylene terephthalate, polytrimethylene terephthalate, and polybutylene terephthalate, polyethylene Nonwoven fabric or paper comprising at least one selected from the group of fibers, polypropylene fibers, natural cellulose fibers such as wood pulp and cotton linter, regenerated cellulose fibers such as viscose rayon and copper ammonia rayon, and purified cellulose fibers such as lyocell and tencel. It is. From the viewpoint of impregnation properties such as an electrolytic solution, cellulose is preferable. In addition, as the base material layer, a melt blown or electrospinning nonwoven fabric can be suitably used in the film thickness range defined in the present embodiment, and a base material that has been thinned by calendaring is more preferably used.

  An insulating porous film may be formed on one side or both sides of the separator of this embodiment. In the case of an electrical storage device, when local heat is generated inside the battery due to an internal short circuit or the like, the separator around the heat generating part contracts, the internal short circuit further expands, and a runaway heat is generated, causing severe ignition or rupture. It can lead to an event. By forming the insulating porous film on one or both sides of the separator, it is possible to prevent the occurrence or expansion of a short circuit and provide a highly safe power storage device.

  The insulating porous film formed on one side or both sides of the separator of the present embodiment is composed of an inorganic filler and a thermosetting resin, and the thermosetting resin does not embed the inorganic filler and holds the voids between the inorganic fillers. Preferably it is. Examples of the inorganic filler include calcium oxide, sodium carbonate, alumina, gibbsite, boehmite, magnesium oxide, magnesium hydroxide, silica, titanium oxide, barium titanate, zirconium oxide, and other inorganic oxides, inorganic hydroxides, and aluminum nitride. Or at least one selected from the group consisting of inorganic nitrides such as silicon nitride, calcium fluoride, barium fluoride, barium sulfate, silicon, aluminum compounds, zeolite, apatite, kaolin, mullite, spinel, olivine, mica, and montmorillonite Can be.

Examples of thermosetting resins include epoxy resins, acrylic resins, oxetane resins, unsaturated polyester resins, alkyd resins, novolac resins, resol resins, urea resins, melamine resins, and the like. These can be used alone, or two or more of them can be used in combination. These thermosetting resins are preferably water dispersions in terms of ease of handling and safety. The aqueous dispersion may contain a dispersant, an emulsifier, an organic solvent and the like as necessary. Examples of the epoxy resin include copolymers such as glycidyl acrylate, acrylic acid, methyl methacrylate, methacrylic acid, butyl methacrylate, and styrene. Examples of the acrylic resin include copolymers such as methyl methacrylate, butyl acrylate, methacrylic acid, hydroxyethyl methacrylate, and styrene.
The insulating porous film formed on one side or both sides of the separator of this embodiment is prepared by bringing a mixed slurry of an inorganic filler and a thermosetting resin into contact with a nonwoven fabric substrate and drying it, and is fixed to the cellulose fine fiber layer. . You may add a thickener, an antifoamer, and an organic solvent to a mixing slurry as needed.

The insulating porous film formed on one or both sides of the separator of the present embodiment preferably has a basis weight of 2 g / m ² or more and 10 g / m ² or less. If the basis weight is 2 g / m ² , pinholes may be generated. On the other hand, if the basis weight is greater than 10 g / m ² , the insulating layer becomes too thick and the internal resistance increases, Powder fall and peeling may occur. The content of the inorganic filler in the separator is preferably 15.0 to 50.0% by weight, and the solid content of the thermosetting resin in the separator is preferably 1.0 to 15.0% by weight. . If the content of the inorganic filler is less than 10.0% by mass and the solid content of the thermosetting resin is more than 20.0% by mass, pinholes may be generated. If the content of the inorganic filler is more than 70.0% by mass and the solid content of the thermosetting resin is less than 0.1% by mass, the inorganic filler may fall off or peel off.

  In the separator of this embodiment, it is preferable that the chlorine ion containing concentration used as one scale of the amount of contained metal ions is 40 ppm or less depending on a use. When the chlorine ion content is 40 ppm or less, metal ions such as Na and Ca are also contained at a relatively low concentration. As a result, the heat resistance of the separator and the electrical characteristics of the electricity storage device incorporating the separator are included. This is because it is possible to suppress the inhibition of. When the chloride ion-containing concentration is more preferably 30 ppm or less, and even more preferably 25 ppm or less, heat resistance is more suitably exhibited. The chloride ion concentration can be evaluated by ion chromatography.

The main production method of the separator of the present embodiment includes forming a dispersion liquid obtained by highly dispersing regenerated cellulose fine fibers in a dispersion medium such as water by a papermaking method or a coating method. It is preferable to form a film by a papermaking method from the viewpoint of the efficiency of the film forming method such as load. Conventionally, in order to produce a separator with high porosity from fine cellulose fibers, water in the wet paper formed by papermaking was replaced with an organic solvent in order to suppress fusion and aggregation between the fibers during drying. It was necessary to dry later or to use a dispersion containing an organic solvent as a coating liquid for coating (see Japanese Patent No. 4753874). However, in the present invention, by containing a predetermined amount of regenerated cellulose fine fibers having a specific surface area equivalent diameter of 0.20 μm or more and 0.45 μm or less, it is necessary as a separator by a papermaking method or a coating method without using an organic solvent. It has been found that the pores can be retained during drying. Here, the regenerated cellulose fine fiber having a specific surface area equivalent diameter of 0.20 μm or more and 0.45 μm or less is a single-layer papermaking (weight per unit: 10 g / m ² ) from an aqueous dispersion containing only the corresponding regenerated cellulose fine fiber. This means a regenerated cellulose fine fiber having a specific surface area equivalent fiber diameter of 0.20 μm or more and 0.45 μm or less calculated from the specific surface area measurement by the BET method of the single layer sheet obtained when the film is formed. The specific surface area equivalent fiber diameter is preferably 0.25 μm or more and 0.43 μm or less, more preferably 0.25 μm or more and 0.40 μm or less. When the fiber diameter corresponding to the specific surface area is smaller than 0.20 μm, it becomes difficult to keep pores suitable as a separator from drying from the aqueous wet paper, and when the fiber diameter corresponding to the specific surface area is larger than 0.45 μm. Problems are likely to occur in terms of short circuit resistance.
When manufacturing the separator of the present embodiment, a dispersion method for highly dispersing cellulose fine fibers as an aqueous dispersion for papermaking or coating is also important, and the selection is made with a uniform thickness of the separator described later. It greatly affects sex.

  The dispersion containing the regenerated cellulose fine fiber obtained by the fibrillation treatment or the refinement treatment by the production method described above is used as it is or diluted with water and dispersed by an appropriate dispersion treatment, and the separator of this embodiment It can be used as a dispersion for paper making or for coating. Components other than regenerated cellulose fine fibers, for example, natural cellulose fine fibers, fine fibers composed of organic polymers other than cellulose, or reactive cross-linking agents may be mixed at any timing in each step of the dispersion production described above. It may be desirable to add it at the stage of producing a papermaking or coating dispersion. The components are mixed and then dispersed by an appropriate dispersion treatment to obtain a dispersion for papermaking or coating. In particular, regarding the timing of mixing fine fibers other than regenerated cellulose fine fibers, it may be mixed with regenerated cellulose raw material (cut yarn) in the beating process from the pulp or cut yarn stage, and beaten, or the beaten raw material You may mix in the process of performing the refinement | miniaturization process by a high pressure homogenizer. Although any dispersion method may be used after dilution of the papermaking or coating dispersion or after mixing the raw materials, it is appropriately selected according to the contents of the mixed raw material components. For example, a disper-type stirrer, various homomixers, various line mixers and the like can be mentioned, but the invention is not limited to these.

Hereinafter, the film forming method mainly by the papermaking method will be described.
The paper making method can be carried out using not only a batch type paper machine but also all industrially available continuous paper machines. In particular, the composite sheet material of the present invention can be suitably produced by an inclined wire type paper machine, a long net type paper machine, or a round net type paper machine. In order to improve film quality uniformity, use one or more machines (for example, an inclined wire type paper machine is used for the base layer paper and a round net type paper machine is used for the upper layer paper machine). It is also effective in some cases. The papermaking multistage, for example, by performing carried out papermaking with a basis weight of 5 g / m ² in the first stage, the thus obtained wet the second stage of the paper of 5 g / m ² on paper, total 10 g / m ² This is a technique for obtaining a composite sheet material having a basis weight of In the case of multi-stage papermaking, when the upper layer and the lower layer are formed from the same dispersion, it becomes a single-layer composite sheet material. However, in the first stage as the lower layer, for example, fine moisture using fibrillated fibers. It is also possible to form a paper layer, perform paper making with the dispersion described above in the second stage, and allow the lower wet paper to function as a filter to be described later.

Since the separator of the present embodiment uses fine fibers, it is preferable to use a filter cloth or a plastic wire having a fine structure in which fine fibers do not come out during paper making when forming a film by a paper making method. As a filter cloth or plastic wire having such a fine structure, basically, the solid content in the dispersion for papermaking stops as wet paper, that is, 90% by weight as the solid content yield in the papermaking process. As described above, industrially suitable production is possible by selecting a filter cloth or plastic wire that is preferably 95% by weight or more, more preferably 99% by weight or more. A high yield also means that the bite into the filter is low, which is preferable in that the peelability after papermaking becomes good. In addition, it is desirable to reduce the filter mesh size because the yield is improved. However, if the filterability is deteriorated, it is not preferable because the production rate of wet paper is reduced. That is, the water permeation amount of wire mesh or cloth under 25 ° C. atmospheric pressure, is preferably 0.005ml / cm ² · s or more, more preferably 0.01ml / cm ² · s or more, productivity From this point of view, it is possible to make a suitable paper. In practice, it is preferable to select a filter cloth or plastic wire having a high solid content and good drainage. Although the filter cloth and plastic wire which satisfy | fill said conditions are limited, For example, TETEXMONODW07-8435-SK010 (product made from PET) made by SEFAR (Switzerland), NT20 (PET / nylon blend) made by Shikishima canvas company as a filter cloth, Examples thereof include, but are not limited to, plastic wire LTT-9FE manufactured by Nippon Filcon Co., Ltd. and multilayered wires described in JP2011-42903A. A filter cloth satisfying the above-described conditions for a dispersion for papermaking prepared with a fine cellulose fiber concentration of 0.01 wt% or more and 0.5 wt% or less, more preferably 0.05 wt% or more and 0.3 wt% or less The wet paper having a solid content of 4% by weight or more of the cellulose fibers can be produced by depositing on the filter cloth by filtering by operating suction or the like. The solid content in this case is preferably as high as possible, preferably 8% by weight or more, and more preferably 12% by weight or more. By further pressing the wet paper, the dispersion medium in the papermaking dispersion can be removed with high efficiency, and the solid content in the resulting wet film can be increased. Can be obtained. After that, a drying process is performed by a drying facility such as a drum dryer, and the separator is wound up. In the drying step, the separator of this embodiment can be obtained by drying the wet paper. Drying is usually performed under atmospheric pressure in a drum dryer or a pin tenter type hot air drying chamber, but depending on circumstances, drying under pressure or vacuum may be performed. At this time, it is more preferable to dry the wet paper with a drum dryer that can be effectively dried for a fixed length for the purpose of ensuring uniformity of physical properties and suppressing shrinkage in the width direction. What is necessary is just to select a drying temperature suitably in the range of 60 to 150 degreeC. In some cases, multi-stage drying such as rough drying at a low temperature of about 60 to 80 ° C. to give the wet paper self-supporting property and the main drying step at 100 ° C. or more may be effective in operation. is there.

  In order to continuously form the separator according to this embodiment, it is often effective to continuously perform the paper making process and the drying process as described above, and in some cases, the smoothing process by a calendar process. By performing a smoothing process using a calendar device, the above-described thinning can be achieved, and a wide range of separators with a combination of film thickness / air resistance / strength can be provided. As the calendar device, in addition to a normal calendar device using a single press roll, a super calendar device having a structure in which these are installed in a multistage manner may be used. By selecting the material (material hardness) and the linear pressure on both sides of the roll during the calendar process, these separators according to the present invention having various physical property balances can be obtained.

  Also, in the above-mentioned film-forming process by papermaking, the papermaking filter cloth or plastic wire to be used is an endless specification, and the entire process is performed with one wire, or the endless filter or endless of the next process is performed on the way. The felt cloth can be picked up and transferred or transferred, or the whole film forming process or a part of the film forming process can be made a roll-to-roll process using a filter cloth. But the manufacturing method of the separator of this embodiment is not limited to this.

  The separator of this embodiment requires essentially all primary batteries, secondary batteries (for example, lithium secondary ion batteries), electrolytic capacitors (aluminum electrolytic capacitors), electric double layer capacitors, or separators as constituent members. It can be applied to new electricity storage devices (for example, devices described in Japanese Patent Application Laid-Open No. 2004-077931), and the electrode type of the electricity storage device is generally used such as a wound type, a coin type, and a laminated type. It can be applied in almost any style. In addition, the performance of the separator for an electricity storage device of the present embodiment is suitably exhibited particularly in an electric double layer capacitor, a liquid or solid aluminum electrolytic capacitor, a lithium ion secondary battery, or a lithium ion capacitor. The reason is as follows. For example, in an electric double layer capacitor, a general electricity storage device has a structure of electrode / electrolyte / separator / electrolyte / electrode, whereas the portion of the electrolyte in the structure is several μm to several tens μm. The activated carbon layer impregnated with the particle-based electrolytic solution is replaced with a structure. Since the activated carbon layer substantially functions as an electrode, the electrode layer is close to the middle of the separator, and the electrode has a fine particle laminated structure, so that it is easy to cause a so-called short circuit through the separator. In addition, due to the problem of the durability of the electrolytic solution, it is necessary to completely remove the moisture in the activated carbon that is very hygroscopic in the manufacturing process of the electric double layer capacitor. Normally, the assembly process of the electric double layer is to remove the moisture after making a laminated structure other than the electrolyte, and finally inject the electrolyte. Therefore, in the drying process for removing moisture, the activated carbon layer including the separator Will be exposed to high temperatures. In the drying process, in order to completely remove water in the activated carbon, drying is often performed under conditions of 150 ° C. or higher. That is, the separator is required to have heat resistance enough to withstand this condition. As described above, the power storage device separator of the present embodiment has particularly excellent performance in terms of short-circuit resistance and heat resistance, and thus functions particularly favorably in an electric double layer capacitor. Furthermore, the separator according to the present embodiment works extremely favorably also in other power storage devices such as a lithium secondary ion battery using an organic electrolyte solution, similarly to the electric double layer capacitor.

Next, the lithium ion capacitor of this embodiment will be described in detail.
The lithium ion capacitor of the present embodiment includes a negative electrode body in which a negative electrode active material layer containing a carbon material as a negative electrode active material is disposed on a negative electrode current collector;
A positive electrode body in which a positive electrode active material layer including a positive electrode active material made of a carbon material or a carbon compound material is installed on a positive electrode current collector;
An electrode laminate comprising: laminating or winding; and a non-aqueous electrolyte containing a lithium ion-containing electrolyte;
Is housed in an exterior body.

<Negative electrode>
The negative electrode body used in the capacitor of the present embodiment is obtained by providing a negative electrode active material layer on a negative electrode current collector. The negative electrode current collector is preferably a metal foil, more preferably a copper foil having a thickness of 1 to 100 μm.
The negative electrode active material layer contains a negative electrode active material and a binder, and optionally contains a conductive filler. The negative electrode active material is a carbon material that can occlude and release lithium ions. In addition to the carbon material, the negative electrode current collector can contain other materials that occlude and release lithium ions, such as lithium titanium composite oxides and conductive polymers. Examples of the carbon material include non-graphitizable carbon, graphitizable carbon, and composite porous material.

<Negative electrode 1>
The negative electrode active material is preferably a composite porous material obtained by depositing a carbon material on the surface of activated carbon. The composite porous material can be obtained, for example, by heat-treating activated carbon and a carbon material precursor in the coexistence state.
Regarding the activated carbon used as a raw material for the composite porous material, as long as the obtained composite porous material exhibits desired characteristics, there are no particular restrictions on the raw material for obtaining the activated carbon, and petroleum-based, coal-based, plant-based, Commercial products obtained from various raw materials such as molecular systems can be used. In particular, it is preferable to use activated carbon powder having an average particle diameter of 1 μm or more and 15 μm or less. The average particle diameter is more preferably 2 μm or more and 10 μm or less. The average particle size in the present embodiment is the particle at which the cumulative curve is 50% when the cumulative curve is determined with the total volume being 100% when the particle size distribution is measured using a particle size distribution measuring device. The diameter is 50%, and the 50% diameter (Median diameter) is indicated. This average particle diameter can be measured with a commercially available laser diffraction particle size distribution analyzer.

  On the other hand, a carbon material precursor used as a raw material for the composite porous material is an organic material that can be dissolved in a solid, liquid, or solvent, which can be subjected to heat treatment to deposit the carbon material on activated carbon. Examples thereof include synthetic resins such as pitch, mesocarbon microbeads, coke, and phenol resin. Among these carbon material precursors, it is preferable in terms of production cost to use an inexpensive pitch. Pitch is roughly divided into petroleum pitch and coal pitch. Examples of petroleum pitches include crude oil distillation residue, fluid catalytic cracking residue (decant oil, etc.), bottom oil derived from thermal crackers, ethylene tar obtained during naphtha cracking, and the like.

  When the pitch is used, the composite porous material is obtained by depositing a carbon material on the activated carbon by thermally reacting the volatile component or pyrolysis component of the pitch on the surface of the activated carbon. In this case, at a temperature of about 200 ° C. to 500 ° C., the deposition of pitch volatile components or pyrolysis components into the activated carbon pores proceeds, and at 400 ° C. or higher, the reaction that the deposited components become carbon materials proceeds. To do. The peak temperature during the heat treatment is appropriately determined according to the characteristics of the composite porous material to be obtained, the thermal reaction pattern, the thermal reaction atmosphere, etc., but is preferably 400 ° C. or higher, more preferably 450 ° C. to 1000 ° C. The temperature is about 500C, more preferably about 500C to 800C. Moreover, the time which maintains the peak temperature at the time of heat processing should just be 30 minutes-10 hours, Preferably they are 1 hour-7 hours, More preferably, they are 2 hours-5 hours. For example, when heat treatment is performed for 2 hours to 5 hours at a peak temperature of about 500 ° C. to 800 ° C., the carbon material deposited on the activated carbon surface is considered to be a polycyclic aromatic hydrocarbon. .

Examples of the method for producing a composite porous material include a method in which activated carbon is heat-treated in an inert atmosphere containing a hydrocarbon gas volatilized from a carbon material precursor, and the carbon material is deposited in a gas phase. In addition, a method in which activated carbon and a carbon material precursor are mixed and heat-treated in advance, or a method in which a carbon material precursor dissolved in a solvent is applied to activated carbon and dried and then heat-treated is also possible.
The composite porous material is obtained by depositing a carbon material on the surface of activated carbon, but the pore distribution after the carbon material is deposited inside the pores of activated carbon is important. It can be defined by the pore volume. In the present invention, the ratio of mesopore amount / micropore amount is particularly important as well as the absolute values of mesopore amount and micropore amount. That is, in one embodiment of the present invention, the amount of mesopores derived from pores having a diameter of 20 to 500 mm calculated by the BJH method in the above composite porous material was calculated by Vm1 (cc / g) and MP method. When the amount of micropores derived from pores having a diameter of less than 20 mm is Vm2 (cc / g), 0.010 ≦ Vm1 ≦ 0.250, 0.001 ≦ Vm2 ≦ 0.200, and 1.5 ≦ Vm1 / It is preferable that Vm2 ≦ 20.0.

  The mesopore amount Vm1 is more preferably 0.010 ≦ Vm1 ≦ 0.225, and further preferably 0.010 ≦ Vm1 ≦ 0.200. About micropore amount Vm2, 0.001 <= Vm2 <= 0.150 is more preferable, and 0.001 <= Vm2 <= 0.100 is still more preferable. The ratio of mesopore amount / micropore amount is more preferably 1.5 ≦ Vm1 / Vm2 ≦ 15.0, and further preferably 1.5 ≦ Vm1 / Vm2 ≦ 10.0. If the mesopore volume Vm1 is less than or equal to the upper limit (Vm1 ≦ 0.250), high charge / discharge efficiency with respect to lithium ions can be maintained, and the mesopore volume Vm1 and the micropore volume Vm2 are equal to or greater than the lower limit (0.010 ≦ Vm1, 0. If 001 ≦ Vm2), high output characteristics can be obtained.

  Also, in the mesopores with a large pore diameter, the ion conductivity is higher than that of the micropores. Therefore, the mesopore amount is necessary to obtain high output characteristics, while in the micropores with a small pore diameter, Since impurities such as moisture that are considered to have an adverse effect on durability are difficult to desorb, it is considered necessary to control the amount of micropores in order to obtain high durability. Therefore, it is important to control the ratio between the amount of mesopores and the amount of micropores. When the ratio is equal to or higher than the lower limit (1.5 ≦ Vm1 / Vm2), that is, the carbon material is deposited on the micropores more than the mesopores of activated carbon. When the composite porous material after deposition has a large amount of mesopores and a small amount of micropores, high energy density, high output characteristics and high durability (cycle characteristics, float characteristics, etc.) can be obtained. When the ratio between the mesopore amount and the micropore amount is not more than the upper limit (Vm1 / Vm2 ≦ 20.0), high output characteristics can be obtained.

In the present invention, the micropore volume and mesopore volume are values determined by the following method. That is, the sample is vacuum-dried at 500 ° C. all day and night, and the adsorption and desorption isotherm is measured using nitrogen as an adsorbate. Using the isotherm on the desorption side at this time, the micropore volume is calculated by the MP method, and the mesopore volume is calculated by the BJH method.
The MP method uses a “t-plot method” (BC Lippens, JH de Boer, J. Catalysis, 4319 (1965)), and uses a micropore volume, a micropore area, and a micropore. Is a method for obtaining the distribution of M.M. It is a method devised by Mikhail, Brunauer, Bodor (RS Mikhal, S. Brunauer, EE Bodor, J. Colloid Interface Sci., 26, 45 (1968)). The BJH method is a calculation method generally used for analysis of mesopores and was proposed by Barrett, Joyner, Halenda et al. (EP Barrett, LG Joyner and P. Halenda, J Amer. Chem. Soc., 73, 373 (1951)).
In the present embodiment, as described above, the ratio of the mesopore amount / micropore amount after the carbon material is deposited on the surface of the activated carbon is important. In order to obtain a composite porous material having a pore distribution range defined in the present invention, the pore distribution of activated carbon used as a raw material is important.

In the activated carbon used for forming the composite porous material as the negative electrode active material, the mesopore amount derived from the pores having a diameter of 20 to 500 mm calculated by the BJH method is V1 (cc / g), the diameter calculated by the MP method. When the amount of micropores derived from pores less than 20 mm is V2 (cc / g), 0.050 ≦ V1 ≦ 0.500, 0.005 ≦ V2 ≦ 1.000, and 0.2 ≦ V1 / V2 It is preferable that ≦ 20.0.
About mesopore amount V1, 0.050 <= V1 <= 0.350 is more preferable, and 0.100 <= V1 <= 0.300 is still more preferable. The micropore amount V2 is more preferably 0.005 ≦ V2 ≦ 0.850, and further preferably 0.100 ≦ V2 ≦ 0.800. The ratio of mesopore amount / micropore amount is more preferably 0.22 ≦ V1 / V2 ≦ 15.0, and further preferably 0.25 ≦ V1 / V2 ≦ 10.0. When the mesopore volume V1 of the activated carbon is 0.500 or less and when the micropore volume V2 is 1.000 or less, an appropriate amount is obtained to obtain the pore structure of the composite porous material of one embodiment of the present invention. Since it is sufficient to deposit the carbon material, the pore structure tends to be easily controlled. On the other hand, when the mesopore volume V1 of the activated carbon is 0.050 or more, when the micropore volume V2 is 0.005 or more, when V1 / V2 is 0.2 or more, and when V1 / V2 is 20.0. In the following cases, the pore structure of the composite porous material of the present embodiment tends to be easily obtained from the pore distribution of the activated carbon.

The average particle size of the composite porous material in the present embodiment is preferably 1 μm or more and 10 μm or less. About a lower limit, More preferably, it is 2 micrometers or more, More preferably, it is 2.5 micrometers or more. About an upper limit, More preferably, it is 6 micrometers or less, More preferably, it is 4 micrometers or less. If the average particle size is 1 μm or more and 10 μm or less, good durability is maintained. The measurement method of the average particle diameter of said composite porous material is the same as the measurement method used for the average particle diameter of the activated carbon of the above-mentioned positive electrode active material.
In the above composite porous material, the atomic ratio of hydrogen atoms / carbon atoms (hereinafter also referred to as H / C) is preferably 0.05 or more and 0.35 or less, and 0.05 or more and 0.15. The following is more preferable. When H / C is 0.35 or less, the structure (typically polycyclic aromatic conjugated structure) of the carbon material deposited on the activated carbon surface is sufficiently developed. Density) and charge / discharge efficiency are increased. On the other hand, when H / C is 0.05 or more, since carbonization does not proceed excessively, a sufficient energy density can be obtained. H / C is measured by an elemental analyzer.

In addition, the composite porous material usually has an amorphous structure derived from the activated carbon as a raw material and a crystal structure mainly derived from the deposited carbon material. According to the X-ray wide angle diffraction method, the composite porous material preferably has a structure with low crystallinity in order to exhibit high output characteristics, and has a structure with high crystallinity in order to maintain reversibility in charge and discharge. From the (002) plane spacing d ₀₀₂ is 3.60 to 4.00 mm, and the crystallite size Lc in the c-axis direction obtained from the half width of this peak is 8.0 to 20.0 mm. Some are preferable, d ₀₀₂ is 3.60 to 3.75 Å, and the crystallite size Lc in the c-axis direction obtained from the half width of this peak is 11.0 to 16.0 よ り. preferable.
As the binder, for example, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), fluororubber, styrene-butadiene copolymer and the like can be used. 3-20 mass% is preferable with respect to a negative electrode active material, and, as for the mixing amount of the binder in a negative electrode active material layer, the range of 5-15 mass% is further more preferable.

In addition to the lithium ion storable carbon material and the binder, a conductive filler made of a carbonaceous material having higher conductivity than the negative electrode active material can be mixed in the negative electrode active material layer as necessary. Examples of the conductive filler include acetylene black, ketjen black, vapor grown carbon fiber, and a mixture thereof.
0-20 mass% is preferable with respect to a negative electrode active material, and, as for the mixing amount of an electroconductive filler, the range of 1 mass%-15 mass% is further more preferable. The conductive filler is preferably mixed from the viewpoint of high input, but if the mixing amount is more than 20% by mass, the content of the negative electrode active material in the negative electrode active material layer decreases, so the energy density per volume decreases. This is not preferable.
For the negative electrode body, a paste is prepared by dispersing a lithium ion storable carbon material and a binder (if necessary, a conductive filler) in a solvent, and this paste is applied onto the negative electrode current collector and dried. It is obtained by pressing as necessary. As a coating method, the same method as that for the positive electrode body can be used, and a coating method according to the physical properties and coating thickness of the paste can be appropriately selected. The thickness of the negative electrode active material layer is usually about 50 μm to 200 μm.

The negative electrode active material used in the capacitor of this embodiment can be doped with lithium in advance. By pre-doping with lithium, the initial efficiency, capacity, and output characteristics of the capacitor can be controlled. The doping amount is preferably in the range of 30% to 100% of lithium ions that can be occluded by the negative electrode active material, and more preferably in the range of 40% to 80%.
A method for doping lithium ion into the negative electrode active material in advance is not particularly limited, but a known method can be used. For example, after forming a negative electrode active material into an electrode, using the negative electrode body as a working electrode and metallic lithium as a counter electrode, an electrochemical cell combining non-aqueous electrolyte solution is produced, and lithium ions are doped electrochemically. The method of doing is mentioned. It is also possible to dope lithium ions into the negative electrode active material by pressing a metal lithium foil on the negative electrode body and placing it in a non-aqueous electrolyte.

<Negative electrode 2>
The negative electrode active material in the present embodiment is included in the negative electrode active material layer, and
Tripolar cell in which LiPF ₆ is dissolved at 1 mol / L in a solvent in which the working electrode is a negative electrode, the counter electrode is lithium, the reference electrode is lithium, and the electrolytic solution is a mixture of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 1: 4. In this case, lithium is charged with a constant current under the condition that the current value is 100 mA / g per negative electrode active material and the cell temperature is 45 ° C., and the constant voltage is reached when the negative electrode potential becomes 1 mV. The battery is further charged by switching, and the charge amount after a total of 40 hours by constant current and constant voltage charge is the initial lithium charge amount. After the above charge, the current value is 50 mA / g per negative electrode active material, and the cell When the discharge amount when lithium is discharged at a constant current until the negative electrode potential reaches 2.5 V under the condition that the temperature is 45 ° C., the initial lithium charge amount is In the discharge characteristics, the following (1) and (2):
(1) The charge amount is 1100 mAh / g or more and 2000 mAh / g or less; and (2) The discharge amount is 100 mAh / g or more at a negative electrode potential of 0 to 0.5 V;
Is satisfied at the same time.

  As for the above (1), if the charge amount is 1100 mAh / g or more, the amount of the negative electrode active material in the negative electrode can be reduced, the negative electrode active material layer can be made thin, and the energy storage device exhibits a high energy density. If the charge amount is 2000 mAh / g or less, the amount of pores in the negative electrode active material does not increase too much, and the bulk density of the negative electrode active material layer can be increased. More preferably, the charge amount is 1200 mAh / g or more and 1700 mAh / g or less, and still more preferably, the charge amount is 1300 mAh / g or more and 1600 mAh / g or less.

  As for (2) above, when the negative electrode potential is between 0 and 0.5 V and the discharge amount is 100 mAh / g or more, the negative electrode potential operates at a low potential in the charge / discharge process when the battery is used. And high durability can be exhibited. More preferably, the discharge amount between the negative electrode potential of 0 to 0.5 V is 120 mAh / g or more, and more preferably 140 mAh / g or more.

The negative electrode active material in the present embodiment preferably includes a composite porous material in which pitch charcoal is deposited on the surface of activated carbon.
The negative electrode active material containing the composite porous material of the present embodiment is characterized by satisfying the following (i) and (ii) simultaneously:
(I) The weight ratio of the pitch charcoal to the activated carbon is 10% or more and 60% or less, and the softening point of the pitch as a raw material of the pitch charcoal is 100 ° C. or less; and (ii) the negative electrode active material is the BET specific surface area of 350m ² / g~1500m ² / g, and lithium ions, have been 1100mAh / g~2000mAh / g doped per unit weight.

Hereinafter, the above (i) will be described.
If the weight ratio of the pitch charcoal to the activated carbon is 10% or more, the micropores that the activated charcoal has can be appropriately filled with the pitch charcoal, and durability is improved by improving the charge / discharge efficiency of lithium ions. Will not be damaged. Further, if the weight ratio of the carbonaceous material is 60% or less, the specific surface area can be increased by appropriately holding the pores of the composite porous material, and the pre-doping amount of lithium ions can be increased. High power density and high durability can be maintained even if the film is thinned. From the above, this weight ratio is preferably 15% or more and 55% or less, more preferably 18% or more and 50% or less, and particularly preferably 20% or more and 47% or less.
Furthermore, if the softening point of the pitch coal raw material is 100 ° C. or less, it is not bound by theory, but the micropores possessed by the activated carbon can be appropriately filled with the pitch coal. In addition, since the charge / discharge efficiency of the initial lithium charge / discharge characteristics is improved, the discharge amount can be increased when the negative electrode potential is between 0 and 0.5 V, and the durability can be improved. The softening point of the pitch is more preferably 90 ° C. or less, and further preferably 50 ° C. or less. The pitch softening point is preferably about 35 ° C. or higher.

Hereinafter, the above (ii) will be described.
When the specific surface area of the negative electrode active material in the BET method is 350 m ² / g or more, the pores of the negative electrode active material can be appropriately retained, and the doping amount of lithium ions can be increased. Can be realized. On the other hand, when the specific surface area is 1500 m ² / g or less, the micropores of the activated carbon can be appropriately filled, and the charge / discharge efficiency of the initial lithium charge / discharge characteristics is improved, so that the negative electrode potential is 0 to 0.5V. It is possible to increase the amount of discharge when it is between, and durability can be improved. The specific surface area is more preferably 350m ² / g~1100m ² / g, more preferably from 370m ² / g~600m ² / g.

  Further, the negative electrode active material is doped with lithium ions (also referred to as pre-doping). The pre-doping amount is 1100 mAh / g or more and 2000 mAh / g or less per unit weight of the composite porous material. This pre-doping amount is preferably 1200 mAh / g or more and 1700 mAh / g or less, and more preferably 1300 mAh / g or more and 1600 mAh / g or less. By pre-doping with lithium ions, the negative electrode potential is lowered, the cell voltage is increased when combined with the positive electrode, and the utilization capacity of the positive electrode is increased, resulting in higher capacity and higher energy density.

In the negative electrode for a non-aqueous lithium storage element according to this embodiment, if the pre-doping amount is 1100 mAh / g or more, lithium ions are sufficiently present at irreversible sites that cannot be desorbed once lithium ions in the negative electrode material are inserted. Since the amount of the negative electrode active material with respect to the desired lithium amount can be reduced, the negative electrode film thickness can be reduced, and high durability, output characteristics, and high energy density can be obtained. Further, the higher the pre-doping amount, the lower the negative electrode potential and the higher the durability and energy density. However, when the pre-doping amount is 2000 mAh / g or less, there is no possibility that side effects such as precipitation of lithium metal occur.
The negative electrode active material may be used alone or in combination of two or more.

The composite porous material can be obtained, for example, by heat treatment in a state where activated carbon and pitch coexist.
The activated carbon used as a raw material for the composite porous material is not particularly limited as long as the raw material before activated carbon is used as long as the obtained composite porous material exhibits desired characteristics. Commercial products obtained from various raw materials such as molecular systems can be used. It is preferable to use activated carbon powder having an average particle size of 1 μm or more and 15 μm or less, and more preferably the average particle size is 2 μm or more and 10 μm or less.
On the other hand, the pitch used for the raw material of the composite porous material is roughly divided into petroleum pitch and coal pitch. Examples of petroleum pitches include crude oil distillation residue, fluid catalytic cracking residue (such as decant oil), bottom oil from thermal crackers, and ethylene tar obtained during naphtha cracking.

The composite porous material is obtained by depositing pitch charcoal on the activated carbon by thermally reacting the volatile component or pyrolysis component of the pitch on the surface of the activated carbon. In this case, at a temperature of about 200 to 500 ° C., the deposition of pitch volatile components or pyrolysis components into the activated carbon pores proceeds, and at 400 ° C. or higher, the reaction in which the deposited components become pitch charcoal proceeds. . The peak temperature during the heat treatment is appropriately determined depending on the characteristics of the composite porous material to be obtained, the thermal reaction pattern, the thermal reaction atmosphere, etc., but is preferably 400 ° C. or higher, more preferably 450 ° C. to 1000 ° C. ° C, more preferably about 500 to 800 ° C. Moreover, the time which maintains the peak temperature at the time of heat processing should just be 30 minutes-10 hours, Preferably they are 1 hour-7 hours, More preferably, they are 2 hours-5 hours. When heat treatment is performed at a peak temperature of about 500 to 800 ° C. for 2 to 5 hours, the pitch charcoal deposited on the activated carbon surface is considered to be a polycyclic aromatic hydrocarbon.
Examples of the method for producing the composite porous material include a method in which activated carbon is heat-treated in an inert atmosphere containing hydrocarbon gas volatilized from pitch, and pitch charcoal is deposited in the gas phase. Moreover, the method of heat-mixing activated carbon and pitch previously, or the method of heat-processing after apply | coating and drying the pitch melt | dissolved in the solvent on activated carbon can also be utilized.

The composite porous material is obtained by depositing pitch charcoal on the surface of activated carbon, but the pore distribution after the pitch is deposited inside the pores of the activated carbon is important. Can be defined by quantity. That is, the composite porous material has a mesopore amount derived from pores having a diameter of 20 to 500 mm calculated by the BJH method as Vm1 (cc / g), and a micropore derived from pores having a diameter of less than 20 mm calculated by the MP method. When the pore volume is Vm2 (cc / g), the following (I) to (III):
(I) 0.010 ≦ Vm1 ≦ 0.300 and 0.010 ≦ Vm2 ≦ 0.200;
(II) 0.010 ≦ Vm1 ≦ 0.200 and 0.200 ≦ Vm2 ≦ 0.400; and (III) 0.010 ≦ Vm1 ≦ 0.100 and 0.400 ≦ Vm2 ≦ 0.650 ;
It is preferable to satisfy at least one of the following.
If the mesopore amount Vm1 is less than or equal to the upper limit (Vm1 ≦ 0.300), the specific surface area of the composite porous material can be increased, the pre-doping amount of lithium ions can be increased, and the bulk density of the negative electrode As a result, the negative electrode can be thinned. Moreover, if the micropore amount Vm2 is not more than the upper limit value (Vm2 ≦ 0.650), high charge / discharge efficiency for lithium ions can be maintained. On the other hand, if the mesopore volume Vm1 and the micropore volume Vm2 are not less than the lower limit values (0.010 ≦ Vm1, 0.010 ≦ Vm2), high output characteristics can be obtained.
The composite porous material preferably satisfies the above (I) or (II) among the above (I) to (III). In the above (I), the mesopore amount Vm1 is preferably 0.050 ≦ Vm1 ≦ 0.300.

In the present invention, as described above, the amount of mesopores and the amount of micropores after depositing pitch charcoal on the surface of activated carbon is important, but composite porous materials having a pore distribution range defined in the present invention are used. In order to obtain, the pore distribution of the activated carbon used as a raw material is important.
The activated carbon has a mesopore amount derived from pores having a diameter of 20 to 500 mm calculated by the BJH method as V1 (cc / g) and a micropore amount derived from pores having a diameter of less than 20 mm calculated by the MP method. When V2 (cc / g), it is preferable that 0.050 ≦ V1 ≦ 0.500, 0.005 ≦ V2 ≦ 1.000, and 0.2 ≦ V1 / V2 ≦ 20.0.
The amount of mesopores is more preferably 0.050 ≦ V1 ≦ 0.350, and further preferably 0.100 ≦ V1 ≦ 0.300. The amount of micropores is more preferably 0.005 ≦ V2 ≦ 0.850, and further preferably 0.100 ≦ V2 ≦ 0.800. The ratio of mesopore amount / micropore amount is more preferably 0.22 ≦ V1 / V2 ≦ 10.0, and further preferably 0.25 ≦ V1 / V2 ≦ 10.0. When the upper limit is exceeded, that is, when the mesopore volume V1 of the activated carbon is greater than 0.5 and when the micropore volume V2 is greater than 1.0, it is often necessary to obtain the pore structure of the composite porous material of the present invention. Therefore, it is difficult to control the pore structure.

In addition, unlike the general surface coating, the process for producing the composite porous material described above is less likely to occur after the pitch charcoal is deposited on the surface of the activated carbon, and the average particle diameter before and after the deposition is Characterized by almost no change. In the present invention, the amount of micropores and the amount of mesopores are reduced after deposition, as is clear from the characteristics of the above-mentioned process for producing the composite porous material and the examples described later. It can be presumed that most of the volatile component or pyrolysis component of the pitch is deposited in the pores of the activated carbon, and the reaction in which the deposited component becomes pitch charcoal has progressed.
As described above, the average particle diameter of the composite porous material in the present embodiment is almost the same as that of the activated carbon before deposition, but is preferably 1 μm or more and 10 μm or less. About a lower limit, More preferably, it is 2 micrometers or more, More preferably, it is 2.5 micrometers or more. About an upper limit, More preferably, it is 6 micrometers or less, More preferably, it is 4 micrometers or less. If the average particle diameter is 2 μm or more and 10 μm or less, sufficient durability is maintained. The measuring method of the average particle diameter of the composite porous material said here is the same method as the activated carbon used for the above-mentioned raw material.

In the above composite porous material, the average pore diameter is preferably 28 mm or more, more preferably 30 mm or more from the viewpoint of achieving high output characteristics. On the other hand, from the point of obtaining a high energy density, it is preferably 65 mm or less, more preferably 60 mm or less. In this specification, the average pore diameter is obtained by dividing the total pore volume per weight obtained by measuring each equilibrium adsorption amount of nitrogen gas at each relative pressure at the liquid nitrogen temperature by the BET specific surface area. Means something.
In the above composite porous material, the atomic ratio of hydrogen atoms / carbon atoms (hereinafter also referred to as H / C) is preferably 0.05 or more and 0.35 or less, and 0.05 or more and 0.15. The following is more preferable. When H / C exceeds the upper limit, the carbonaceous material polycyclic aromatic conjugated structure deposited on the activated carbon surface is not sufficiently developed, so the capacity (energy density) and charge / discharge efficiency are low. Become. On the other hand, when H / C is lower than the lower limit value, carbonization proceeds excessively, and a sufficient energy density may not be obtained. H / C is measured by an elemental analyzer.

The composite porous material has an amorphous structure derived from the activated carbon as a raw material, but at the same time has a crystal structure mainly derived from the deposited carbonaceous material. According to the X-ray wide-angle diffraction method, the composite porous material has a (002) plane spacing d ₀₀₂ of 3.60 to 4.00 and a c-axis direction crystal obtained from the half width of this peak. preferably has child size Lc is less 20.0Å than 8.0 Å, d ₀₀₂ is less 3.75Å than 3.60A, the crystallite size Lc in the c-axis direction obtained from the half-value width of this peak What is 11.0 to 16.0 is more preferable.
In addition to the negative electrode active material, a conductive filler and a binder can be added to the negative electrode active material layer as necessary. The type of the conductive filler is not particularly limited, and examples thereof include acetylene black, ketjen black, and vapor grown carbon fiber. For example, the addition amount of the conductive filler is preferably 0 to 30% by mass with respect to the negative electrode active material. The binder is not particularly limited, and PVDF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), styrene-butadiene copolymer, and the like can be used. The amount of the binder added is preferably, for example, in the range of 3 to 20% by mass with respect to the negative electrode active material.

A negative electrode for a non-aqueous lithium-type storage element can be manufactured by an electrode molding method such as a known lithium ion battery or an electric double layer capacitor. For example, a negative electrode active material, a conductive filler, and a binder are used as a solvent. It is obtained by dispersing, forming a slurry, applying an active material layer on a current collector, drying, and pressing as necessary. In addition, it is possible to dry-mix without using a solvent and press-mold the active material, and then affix it to the current collector using a conductive adhesive or the like.
The negative electrode for a non-aqueous lithium storage element may have a negative electrode active material layer formed on only one side of the current collector or may be formed on both sides. The thickness of the negative electrode active material layer is 15 μm or more and 45 μm or less per side, preferably 20 μm or more and 40 μm or less. When the thickness is 15 μm or more, sufficient charge / discharge capacity can be exhibited. On the other hand, if the thickness is 45 μm or less, the energy density can be increased by reducing the cell volume.
When the current collector has holes, the thickness of the negative electrode active material layer means an average value of the thickness per one side of the portion of the current collector that does not have holes. In this case, examples of the hole include a punching metal through-hole portion and an expanded metal opening portion.

The bulk density of the negative electrode active material layer is preferably 0.60 g / cm ³ or more and 1.2 g / cm ³ or less, more preferably 0.70 g / cm ³ or more and 1.0 g / cm ³ or less. When the bulk density is 0.60 g / cm ³ or more, sufficient strength can be maintained and sufficient conductivity between the active materials can be expressed. Moreover, if it is 1.2 g / cm < ³ > or less, the void | hole which ion can fully diffuse in an active material layer is securable.
The material of the negative electrode current collector is not particularly limited as long as it does not cause degradation such as elution and reaction when the storage element is formed, and examples thereof include copper, iron, and stainless steel. In the negative electrode for a non-aqueous lithium storage element of the present invention, copper is preferably used as the negative electrode current collector. As the shape of the negative electrode current collector, a metal foil or a structure in which an electrode can be formed in the gap between the metals can be used. Alternatively, a metal foil having a through hole such as an etching foil may be used. The thickness of the negative electrode current collector is not particularly limited as long as the shape or strength of the negative electrode can be sufficiently maintained, but is preferably 1 to 100 μm, for example.

  A known method can be used as a method of pre-doping lithium ions into the negative electrode for a non-aqueous lithium storage element. For example, after forming a negative electrode active material into an electrode, using the negative electrode as a working electrode and metallic lithium as a counter electrode, an electrochemical cell combining non-aqueous electrolyte is prepared, and lithium ions are electrochemically pre-doped. A method is mentioned. It is also possible to pre-dope lithium ions into the negative electrode by pressing a metal lithium foil on the negative electrode and placing it in a non-aqueous electrolyte.

From the viewpoint of providing a negative electrode that is excellent in energy density, output characteristics, and durability, a negative electrode active material obtained by depositing pitch charcoal on the surface of activated carbon includes a composite porous material. (I) and (ii):
(I) The weight ratio of the pitch charcoal to the activated carbon is 10% or more and 60% or less, and the softening point of the pitch as a raw material of the pitch charcoal is 100 ° C. or less; and (ii) the negative electrode active material is the BET specific surface area of 350m ² / g~1500m ² / g, and lithium ions, have been 1100mAh / g~2000mAh / g doped per unit weight;
It is preferable to satisfy.
More specifically, in order to improve energy density [capacitance of storage element (mAh) / negative electrode volume (cm ³ )], the thickness of the negative electrode active material layer is adjusted to 15 μm or more and 45 μm or less, and pitch charcoal / It is preferable to adjust the activated carbon (weight ratio) and the softening point of the pitch within a range that does not impair the durability of the negative electrode and can increase the pre-doping amount of lithium ions.

<Positive electrode>
The positive electrode for a non-aqueous lithium storage element in this embodiment is obtained by providing a positive electrode active material layer on a positive electrode current collector.
<Positive electrode active material>
The positive electrode active material layer contains a positive electrode active material and a binder, and optionally contains a conductive filler. As the positive electrode active material, the following activated carbon 1 or activated carbon 2 is preferably used.

(Activated carbon 1)
There are no particular restrictions on the type of activated carbon 1 and its raw materials, but in order to achieve both high capacity (ie high energy density) and high output characteristics (ie high output density), the pores of the activated carbon are optimally controlled. It is preferable to do. Specifically, the amount of mesopores derived from pores having a diameter of 20 to 500 mm calculated by the BJH method is V1 (cc / g), and the amount of micropores derived from pores having a diameter of less than 20 mm calculated by the MP method is calculated. When V2 (cc / g) is satisfied, 0.3 <V1 ≦ 0.8 and 0.5 ≦ V2 ≦ 1.0 are satisfied, and the specific surface area measured by the BET method is 1500 m ² / g or more and 3000 m ^2. Activated carbon that is less than / g is preferred.
The mesopore amount V1 is preferably a value larger than 0.3 cc / g from the viewpoint of increasing the output characteristics when the positive electrode material is incorporated in the power storage element, and also from the viewpoint of suppressing a decrease in the capacity of the power storage element. , Preferably 0.8 cc / g or less. The V1 is more preferably 0.35 cc / g or more and 0.7 cc / g or less, and further preferably 0.4 cc / g or more and 0.6 cc / g or less.
On the other hand, the micropore amount V2 is preferably 0.5 cc / g or more in order to increase the specific surface area of the activated carbon 1 and increase the capacity, and also suppresses the bulk of the activated carbon 1 to reduce the density as an electrode. From the viewpoint of increasing the capacity per unit volume, it is preferably 1.0 cc / g or less. The V2 is more preferably 0.6 cc / g or more and 1.0 cc / g or less, and further preferably 0.8 cc / g or more and 1.0 cc / g or less.

Further, the ratio (V1 / V2) of the mesopore amount V1 to the micropore amount V2 is preferably in the range of 0.3 ≦ V1 / V2 ≦ 0.9. That is, V1 / V2 is preferably 0.3 or more from the viewpoint of increasing the ratio of the mesopore amount to the micropore amount to such an extent that the decrease in output characteristics can be suppressed while obtaining a high capacity. V1 / V2 is preferably 0.9 or less from the viewpoint of increasing the ratio of the micropore amount to the mesopore amount so that the decrease in capacity can be suppressed while obtaining high output characteristics. A more preferable range of V1 / V2 is 0.4 ≦ V1 / V2 ≦ 0.7, and a more preferable range of V1 / V2 is 0.55 ≦ V1 / V2 ≦ 0.7.
Here, the amount of micropores and the amount of mesopores of activated carbon 1 are values obtained by the same method as for the composite porous material described above.

The average pore diameter of the activated carbon 1 is preferably 17 mm or more, more preferably 18 mm or more, and further preferably 20 mm or more from the viewpoint of maximizing the output. Further, from the point of maximizing the capacity, it is preferably 25 mm or less. The average pore diameter described in the present specification is obtained by dividing the total pore volume per weight obtained by measuring each equilibrium adsorption amount of nitrogen gas at each relative pressure at the liquid nitrogen temperature by the BET specific surface area. Point to what you asked for.
BET specific surface area of the activated carbon 1 is preferably from 1500 m ² / g or more 3000 m ² / g, more preferably not more than 1500 m ² / g or more 2500 m ² / g. When the BET specific surface area is 1500 m ² / g or more, good energy density is easily obtained. On the other hand, when the BET specific surface area is 3000 m ² / g or less, a large amount of binder is used to maintain the strength of the electrode. Since it is not necessary to put in, there exists a tendency for the performance per electrode volume to become high.
The activated carbon 1 having the above-described characteristics can be obtained using, for example, the raw materials and processing methods described below.

In this embodiment, the carbon source used as a raw material of the activated carbon 1 is not particularly limited, and for example, plant-based raw materials such as wood, wood flour, coconut shell, by-products during pulp production, bagasse, and molasses; Peat, lignite, lignite, bituminous coal, anthracite, petroleum distillation residue components, petroleum pitch, coke, coal tar and other fossil raw materials; phenol resin, vinyl chloride resin, vinyl acetate resin, melamine resin, urea resin, resorcinol resin, celluloid, Various synthetic resins such as epoxy resins, polyurethane resins, polyester resins, polyamide resins; synthetic rubbers such as polybutylene, polybutadiene, and polychloroprene; other synthetic woods, synthetic pulps, and carbides thereof. Among these raw materials, plant-based raw materials such as coconut shells and wood flour, and carbides thereof are preferable, and coconut shell carbides are particularly preferable.
As a carbonization and activation method for making these raw materials into the activated carbon 1, known methods such as a fixed bed method, a moving bed method, a fluidized bed method, a slurry method, and a rotary kiln method can be employed.
As a carbonization method of these raw materials, nitrogen, carbon dioxide, helium, argon, xenon, neon, carbon monoxide, an exhaust gas such as combustion exhaust gas, or other gases mainly composed of these inert gases. The method of baking for about 30 minutes-about 10 hours at about 400-700 degreeC (preferably 450-600 degreeC) using mixed gas is mentioned.

As a method for activating the carbide obtained by the carbonization method, a gas activation method in which firing is performed using an activation gas such as water vapor, carbon dioxide, or oxygen is preferably used. Among these, a method using water vapor or carbon dioxide as the activation gas is preferable.
In this activation method, the carbide is supplied for 3 to 12 hours (preferably 5 to 11) while supplying the activation gas at a rate of 0.5 to 3.0 kg / h (preferably 0.7 to 2.0 kg / h). It is preferable to activate by heating to 800 to 1000 ° C. over a period of time, more preferably 6 to 10 hours.
Furthermore, prior to the activation treatment of the carbide, the carbide may be activated in advance. In this primary activation, it is usually possible to activate the gas by firing the carbon material at a temperature below 900 ° C. using an activation gas such as water vapor, carbon dioxide or oxygen.
By appropriately combining the calcination temperature and calcination time in the carbonization method, the activation gas supply amount, the temperature increase rate, and the maximum activation temperature in the activation method, the activated carbon 1 having the above characteristics that can be used in the present embodiment is manufactured. be able to.

The average particle diameter of the activated carbon 1 is preferably 1 to 20 μm. The average particle size described in the present specification is the particle at which the cumulative curve becomes 50% when the cumulative curve is determined with the total volume being 100% when the particle size distribution is measured using a particle size distribution measuring device. Diameter (ie 50% diameter (Median diameter)).
When the average particle size is 1 μm or more, the capacity per electrode volume tends to increase because the density of the active material layer is high. On the other hand, when the average particle size is 20 μm or less, it tends to be suitable for high-speed charge / discharge. Furthermore, the average particle diameter is more preferably 2 to 15 μm, and further preferably 3 to 10 μm.

(Activated carbon 2)
The positive electrode active material has a mesopore amount derived from pores having a diameter of 20 to 500 mm calculated by the BJH method as V1 (cc / g) and a micropore amount derived from pores having a diameter of less than 20 mm calculated by the MP method. When V2 (cc / g) is set, it is preferable to include activated carbon 2 that satisfies 0.8 <V1 ≦ 2.5 and 0.92 <V2 ≦ 3.0.
The mesopore amount V1 is preferably a value larger than 0.8 cc / g from the viewpoint of increasing the output characteristics when the positive electrode material is incorporated in the power storage element, and from the viewpoint of suppressing a decrease in the capacity of the power storage element. It is preferable that it is 2.5 cc / g or less. V1 is more preferably 1.00 cc / g or more and 2.0 cc / g or less, and further preferably 1.2 cc / g or more and 1.8 cc / g or less.
On the other hand, the micropore volume V2 is preferably larger than 0.92 cc / g in order to increase the specific surface area of the activated carbon 2 and increase the capacity, and to increase the density of the activated carbon 2 as an electrode. From the viewpoint of increasing the capacity per unit volume, it is preferably 3.0 cc / g or less. V2 is more preferably greater than 1.0 cc / g and not greater than 2.5 cc / g, and still more preferably not less than 1.5 cc / g and not greater than 2.5 cc / g.

The activated carbon 2 having the mesopore amount and the micropore amount described above has a higher BET specific surface area than the activated carbon used for conventional electric double layer capacitors or lithium ion capacitors. Specific values of the BET specific surface area are 2600 m ² / g or more and 4500 m ² / g or less, and preferably 3000 m ² / g or more and 4000 m ² / g or less. When the BET specific surface area is 2600 m ² / g or more, good energy density is easily obtained. On the other hand, when the BET specific surface area is 4500 m ² / g or less, a large amount of binder is used to maintain the strength of the electrode. Since it is not necessary to put in, the performance per electrode volume tends to be high.

The activated carbon 2 having the characteristics as described above can be obtained using, for example, the raw materials and processing methods described below.
The carbonaceous material used as a raw material for the activated carbon 2 is not particularly limited as long as it is a carbon source that is usually used as a raw material for activated carbon. For example, plant-based raw materials such as wood, wood flour, and coconut shells; Examples include fossil raw materials such as coke; various synthetic resins such as phenol resin, furan resin, vinyl chloride resin, vinyl acetate resin, melamine resin, urea resin, and resorcinol resin. Among these raw materials, phenol resin and furan resin are particularly preferable because they are suitable for producing activated carbon 2 having a high specific surface area.
Examples of a method for carbonizing these raw materials or a heating method at the activation treatment include known methods such as a fixed bed method, a moving bed method, a fluidized bed method, a slurry method, and a rotary kiln method. The atmosphere at the time of heating is an inert gas such as nitrogen, carbon dioxide, helium, or argon, or a gas mixed with other gases containing these inert gases as a main component. The carbonization temperature is generally about 400 to 700 ° C., and the method of firing for about 0.5 to 10 hours is common.

[Crushing and classification process]
In the present embodiment, it is important to pulverize and classify the carbonaceous material (carbide) in advance before activating it. This is because it can be efficiently activated, and it is possible to prevent deterioration of characteristics due to the nascent interface when pulverized after activation.
A method for previously pulverizing the carbonaceous material will be described below.
The pulverization method may be either dry pulverization or wet pulverization, but wet pulverization is preferable from the viewpoint of pulverization speed, continuous operability and power consumption. In the case of wet grinding, specifically, the following conditions can be employed. First, a sample to be crushed, hard beads such as metal, zirconia and ceramic, and a solvent are put into a hard container such as metal, agate or ceramic, and pulverized. It is preferable that the container can be sealed, and it is preferable to replace the inside of the container with an inert gas such as nitrogen or argon during pulverization. As the solvent, water or an organic solvent can be used, but an organic solvent having a low boiling point is not suitable because there is a risk of ignition. Although the pulverization time is adjusted according to the particle size of the obtained sample, the pulverization for a long time may cause impurities to be mixed. Since the particle size distribution is broadened by pulverization, classification with a sieve is preferable. As a result of classification, in the present invention, classification can be performed between 1 μm and 30 μm. The carbonaceous material obtained in the above pulverization / classification step is carbonized into a carbide by the following method.

As a method for activating the carbide after pulverization / classification, there is a gas activation method in which firing is performed using an activation gas such as water vapor, carbon dioxide, oxygen, or an alkali metal activation method in which heat treatment is performed after mixing with an alkali metal compound. An alkali metal activation method is preferable for producing activated carbon having a high specific surface area. In this activation method, after mixing so that the weight ratio of carbide and an alkali metal compound such as KOH and NaOH is 1: 1 or more, in the range of 600 to 900 ° C. in an inert gas atmosphere, 0.5 to Heating is performed for 5 hours, and then the alkali metal compound is removed by washing with an acid and water, followed by drying.
In the present invention, the mass ratio of carbide to alkali metal compound (= carbide: alkali metal compound) is 1: 1 or more, and the amount of mesopore increases as the amount of alkali metal compound increases. Since there is a tendency for the amount of pores to increase sharply at the boundary, the mass ratio of the alkali metal compound is preferably increased from 1: 3, and is preferably 1: 5.5 or less. As the mass ratio increases, the amount of pores increases as the number of alkali metal compounds increases.
In order to increase the amount of micropores and not increase the amount of mesopores, a larger amount of carbide is mixed with KOH when activated. In order to increase the amount of both pores, KOH is increased with respect to the ratio of carbide to KOH. In order to mainly increase the amount of mesopores, water vapor activation is performed after alkali activation treatment.

The average particle diameter of the activated carbon 2 used in the non-aqueous lithium storage element of this embodiment is 1 μm or more and 30 μm or less, and preferably 2 μm or more and 20 μm or less. More preferably, it is 2 μm or more and 7 μm or less. A mixture of two kinds of activated carbons having different average particle sizes may be used. Here, the average particle size is 50 when the particle size distribution is measured using a particle size distribution measuring device and the cumulative curve is determined with the total volume being 100%. % Diameter, and refers to the 50% diameter (Median diameter).
When the positive electrode active material contains a material other than activated carbon having the specific V1 and V2 (for example, activated carbon not having the specific V1 and V2, a composite oxide of lithium and a transition metal), the specific The content of the activated carbon having V1 and V2 is more than 50% by weight of the total positive electrode active material. The content of the activated carbon having the specific V1 and V2 in the total positive electrode active material is more preferably 70% by weight or more, further preferably 90% by weight or more, and most preferably 100% by weight.

<Other components of positive electrode active material layer and molding of positive electrode>
The positive electrode may have a positive electrode active material layer formed on only one side of the positive electrode current collector or may be formed on both sides. The thickness of the positive electrode active material layer is preferably, for example, 30 μm to 200 μm per side.
The material of the positive electrode current collector is not particularly limited as long as it is a conductive material that does not cause degradation such as elution into the electrolytic solution or reaction when the power storage element is formed. A suitable material is aluminum. As the shape of the positive electrode current collector, a metal foil or a structure (such as a foam) in which an electrode can be formed in a gap between metals can be used. The metal foil may be a normal metal foil having no through hole, or a metal foil having a through hole such as an expanded metal or a punching metal. Further, the thickness of the positive electrode current collector is not particularly limited as long as the shape and strength of the electrode can be sufficiently maintained, but for example, from the viewpoint of strength, conductive resistance, and capacity per volume, 1 to 100 μm is preferable.
The binder used for the positive electrode active material layer is not particularly limited, and PVDF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), a styrene-butadiene copolymer, or the like can be used. The binder content in the positive electrode active material layer is preferably in the range of 3 to 20 parts by mass with respect to 100 parts by mass of the positive electrode active material, for example. Moreover, an electroconductive filler can be added to a positive electrode active material layer as needed. The type of the conductive filler is not particularly limited, and examples thereof include acetylene black, ketjen black, and vapor grown carbon fiber. As for the addition amount of an electroconductive filler, 0-30 mass parts is preferable with respect to 100 mass parts of active materials, for example.

The positive electrode can be manufactured using a known electrode forming technique such as a lithium ion battery or an electric double layer capacitor. For example, a slurry in which a positive electrode active material, a conductive filler, and a binder are dispersed in a solvent, The positive electrode active material layer can be obtained by performing a coating process on the positive electrode current collector, a drying process for drying the solvent, and a pressurizing process for improving the bulk density of the positive electrode active material layer by pressurization.
The bulk density of the positive electrode active material layer is 0.40 g / cm ³ or more, preferably 0.45 g / cm ³ or more, and, 0.70 g / cm ³ or less. When the bulk density is 0.40 g / cm ³ or more, the capacity of the electrode per volume can be increased, and the storage element can be reduced in size. Further, if the bulk density is 0.70 g / cm ³ or less, it is considered that the electrolyte solution is sufficiently diffused in the voids in the positive electrode active material layer and the charge / discharge characteristics at a large current are high.
The bulk density of the positive electrode active material layer used in the present embodiment is compared with the bulk density of the active material layer of ordinary activated carbon produced by the same method due to having a specific amount of micropores and mesopores. small. In that case, in order to achieve the above-mentioned bulk density in a state of being formed as the positive electrode active material layer, for example, the surface temperature is heated by a roll set to a temperature not lower than the melting point of the binder minus 40 ° C. and lower than the melting point. A method of applying pressure (hereinafter also referred to as “heat press”) can be used.

  In addition, a molding process in which activated carbon and a binder are mixed by a dry method without using a solvent, and the mixture is pressed into a plate shape while being heated to a temperature not lower than the melting point of the binder minus 40 ° C. and not higher than the melting point. And an adhering step of attaching the formed positive electrode active material layer to the positive electrode current collector with a conductive adhesive. In addition, melting | fusing point can be calculated | required in the endothermic peak position of DSC (Differential Scanning Calorimetry). For example, using a differential scanning calorimeter “DSC7” manufactured by PerkinElmer Co., Ltd., 10 mg of sample resin is set in a measurement cell, and the temperature is increased from 30 ° C. to 250 ° C. at a temperature increase rate of 10 ° C./min in a nitrogen gas atmosphere. The temperature is raised, and the endothermic peak temperature in the temperature raising process becomes the melting point.

<Electrolyte, packaging materials, etc.>
The non-aqueous electrolyte solution used for the capacitor of this embodiment should just be a non-aqueous liquid containing a lithium ion containing electrolyte. Such a non-aqueous liquid may contain a solvent. Examples of such a solvent include cyclic carbonates represented by ethylene carbonate (EC) and propylene carbonate (PC), diethyl carbonate (DEC), and dimethyl carbonate. (DMC), chain carbonates typified by ethyl methyl carbonate (MEC), lactones such as γ-butyrolactone (γBL), and mixed solvents thereof can be used.
As a salt dissolved in these solvents, lithium salts such as LiBF ₄ and LiPF ₆ can be used. The salt concentration of the electrolytic solution is preferably in the range of 0.5 to 2.0 mol / L. If it is 0.5 mol / L or more, anions are sufficiently present, and the capacitance of the capacitor is maintained. On the other hand, at 2.0 mol / L or less, the salt is sufficiently dissolved in the electrolytic solution, and appropriate viscosity and conductivity of the electrolytic solution are maintained.

In the electrode laminate, one end of the positive electrode terminal is electrically connected to the positive electrode body, and one end of the negative electrode terminal is electrically connected to the negative electrode body. Specifically, the positive electrode terminal is electrically connected to the positive electrode active material layer uncoated region of the positive electrode current collector, and the negative electrode terminal is electrically connected to the negative electrode active material layer uncoated region of the negative electrode current collector. The material of the positive electrode terminal is aluminum, and the material of the negative electrode terminal is preferably nickel-plated copper.
The electrode terminal generally has a substantially rectangular shape, one end of which is electrically connected to the current collector of the electrode laminate, and the other end is connected to an external load (in the case of discharging) or a power source (charging). Electrically connected). Resin such as polypropylene is used to prevent short circuit between the electrode terminal and the metal foil constituting the laminate film and to improve the sealing hermeticity at the center part of the electrode terminal, which becomes the sealing part of the laminate film outer package. It is a preferable aspect that the film made from is affixed.
For example, an ultrasonic welding method is generally used as an electrical connection method between the electrode laminate and the electrode terminal. However, resistance welding, laser welding, or the like may be used, and the method is not limited.

  Moreover, the laminate film used for the exterior body is preferably a film in which a metal foil and a resin film are laminated, and an example of a three-layer structure composed of an outer layer resin film / metal foil / inner layer resin film is exemplified. The outer layer resin film is for preventing the metal foil from being damaged by contact or the like, and a resin such as nylon or polyester can be suitably used. The metal foil is for preventing the permeation of moisture or gas, and a foil of copper, aluminum, stainless steel or the like can be suitably used. The inner layer resin film protects the metal foil from the electrolyte contained therein and is used for melting and sealing at the time of heat sealing. For example, polyolefin, acid-modified polyolefin and the like can be suitably used.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
The structural parameters and physical properties were evaluated as follows.
(1) Evaluation of the maximum fiber diameter of the fiber which comprises a separator About the separator for electrical storage devices, the SEM image was measured and it was judged whether the maximum fiber diameter was 3000 nm or less. The SEM observation uses a FE-SEM, S-800 manufactured by Hitachi, Ltd. for the separator sample on which gold deposition was performed, and the image was captured at a magnification of 10,000 times with an acceleration voltage in the range of 5-10 KV. confirmed.

(2) Measurement of sample thickness Using a Mitutoyo film thickness meter (Model ID-C112XB), a 10 cm × 10 cm square piece was cut out from the separator, and the average value of five measured values at various positions was measured as the film thickness d (μm ).
(3) Measurement of basis weight of fine cellulose sheet Five weights per 1 m ² were calculated from the weight W (g) of the 10.0 cm × 10.0 cm square piece cut out in the above (2) and calculated from the average value. .
(4) Calculation of porosity of molded body From the film thickness d (μm) and weight W (g) of the 10.0 cm × 10.0 cm square piece cut out in (2) above, the porosity of the film Pr (%) was evaluated at 5 points and calculated from the average value.

(5) Specific surface area equivalent fiber diameter measurement After measuring the adsorption amount of nitrogen gas at the boiling point of liquid nitrogen to about 0.2 g of sample with a specific surface area / pore distribution measuring device (manufactured by Beckman Coulter), the same device A specific surface area (m ² / g) is calculated by a program, a cylinder model assuming that the fiber density is not fused at all and a cellulose density is 1.50 g / ml (a cylinder having a circular cross section of the fiber) Based on the formula (fiber diameter = 2.67 / specific surface area) introduced from the surface area / volume ratio with a length of ∝), the fiber diameter corresponding to the specific surface area was calculated from the average value by three evaluations of the specific surface area. .

(6) Measurement of air permeability resistance of membrane Using a Gurley-type densometer (Model G-B2C, manufactured by Toyo Seiki Co., Ltd.), the permeation time (unit: s / 100 ml) of 100 ml of air was measured at room temperature. As an index of film uniformity, the measurement was performed at five points for various positions of the film.
(7) Evaluation of chloride ion-containing concentration Chlorine ion-containing concentration was measured using an ion chromatography apparatus (model: IC-2001) manufactured by Tosoh Corporation.

[Example 1]
Put the tencel cut yarn (3mm length), a regenerated cellulose fiber obtained by Sojitz Corporation, into the washing net, add a surfactant, and rinse the water many times with a washing machine to remove the oil on the fiber surface. did. The obtained refined tencel fiber (cut yarn) was dispersed in water to a solid content of 1.5% by weight (400 L), and SDR14 type laboratory refiner (pressure type DISK) manufactured by Aikawa Tekko Co., Ltd. was used as a disc refiner device. Using a formula, 400 L of the aqueous dispersion was beaten for 20 minutes with a disc clearance of 1 mm. Subsequently, the beating process was continued under conditions where the clearance was reduced to a level almost close to zero. Sampling was performed over time, and the CSF value defined in JIS P 8121 was evaluated for the sampling slurry. The CSF value decreased over time, and once it became close to zero, further beating processing was performed. As we continued, the trend of increasing was confirmed. The beating treatment was continued under the above conditions for about 14 hours after the clearance was nearly zero, and a beating water dispersion (solid content concentration: 1.5% by weight) having a CSF value of 15 ml ↑ was obtained. The obtained beating water dispersion was directly subjected to micronization treatment once and five times under an operating pressure of 100 MPa using a high-pressure homogenizer (NS015H manufactured by Niro Soabi (Italy)). Dispersions M1 and M2 (solid concentration: both 1.5% by weight) were obtained.

Subsequently, the aqueous dispersion M2 was diluted to a solid content concentration of 0.1% by weight and dispersed with a blender. Then, a plain fabric made of PET / nylon blend (NT20, manufactured by Shikishima Canvas Co., Ltd.) Permeation amount: 0.03ml / cm ² · s, batch type paper machine (made by Kumagai Riki Kogyo Co., Ltd., automatic angle) set with fine cellulose fibers and capable of filtering 99% or more by filtration at 25 ° C under atmospheric pressure Using the fine cellulose sheet having a basis weight of 10 g / m ^{2 on} a mold sheet machine (25 cm × 25 cm, 80 mesh) as a guide, the adjusted papermaking slurry was added, and then papermaking (dehydration) was performed at a reduced pressure of 4 KPa with respect to atmospheric pressure.
The wet paper made of the concentrated composition in a wet state on the obtained filter cloth is peeled off from the wire and pressed at a pressure of 1 kg / cm ² for 1 minute, and then the wet paper surface is brought into contact with the drum surface. In the two layers of wet paper / filter cloth, the wet paper is dried for about 120 seconds with the drum dryer having a surface temperature set to 130 ° C. so that the wet paper is in contact with the drum surface. Then, the filter cloth was peeled off from the cellulose sheet-like structure to obtain a sheet (25 cm × 25 cm) composed of white uniform cellulose fine fibers.
Furthermore, the obtained fine cellulose sheet is subjected to a hot press treatment at 150 ° C. × 1.55 t / 20 cm by a calender machine (manufactured by Yuri Roll Co., Ltd.), so that the film thickness is 17 μm, the porosity is 62%, and the chlorine ion is contained. Separator S1 which is a white fine cellulose sheet with a concentration of 19 ppm was obtained.
The structural factor and various physical property values of the separator S1 are shown in Table 1 below.

[Evaluation of lithium ion capacitor performance]
The performance of the lithium ion capacitor using the separator S1 was evaluated.
(Preparation of negative electrode)
The pore distribution was measured using a commercially available coconut shell activated carbon with a pore distribution measuring device (AUTOSORB-1 AS-1-MP) manufactured by Yuasa Ionics Co., Ltd. using nitrogen as an adsorbate. The specific surface area was determined by the BET single point method. Further, as described above, using the isotherm on the desorption side, the mesopore amount was determined by the BJH method, and the micropore amount was determined by the MP method. As a result, the BET specific surface area was 1,780 m ² / g, the mesopore volume (V1) was 0.198 cc / g, the micropore volume (V2) was 0.695 cc / g, V1 / V2 = 0.29, the average fineness. The pore diameter was 21.2 mm. 150g of this activated carbon is placed in a stainless steel mesh basket and placed on a stainless steel bat containing 270g of coal-based pitch (softening point: 50 ° C). It was installed and a thermal reaction was performed. The heat treatment is performed in a nitrogen atmosphere for 8 hours up to 600 ° C., held at the same temperature for 4 hours, subsequently cooled to 60 ° C. by natural cooling, and then taken out from the furnace to be a composite porous material 1 serving as a negative electrode material. Got.

The composite porous material 1 has a weight ratio of the deposited carbonaceous material to activated carbon of 73%, a BET specific surface area of 262 m ² / g, a mesopore volume (Vm1) of 0.180 cc / g, and a micropore volume (Vm2). ) Was 0.0843 cc / g. Furthermore, it was 2.88 micrometers as a result of measuring an average particle diameter using the Shimadzu Corporation laser diffraction type particle size distribution analyzer (SALD-2000J).
Next, 83.4 parts by weight of the composite porous material 4 obtained above, 8.3 parts by weight of acetylene black, 8.3 parts by weight of PVDF (polyvinylidene fluoride) and NMP (N-methylpyrrolidone) are mixed. To obtain a slurry. Next, the obtained slurry was applied to one side of a 15 μm thick copper foil, dried and pressed to obtain a negative electrode having a negative electrode active material layer thickness of 60 μm.
The negative electrode obtained above was cut out to 3 cm ² , and the working electrode was a negative electrode, the counter electrode was lithium, the reference electrode was lithium, the electrolyte was 1 mol in a solvent in which ethylene carbonate and methyl ethyl carbonate were mixed at a volume ratio of 1: 4. A negative electrode of Example 1 was prepared by pre-doping 800 mAh / g of lithium ions with respect to the weight of the composite porous material 1 in a tripolar cell in which LiPF ₆ to be / L was dissolved.
(Preparation of positive electrode)
The crushed palm shell carbonized product was carbonized at 500 ° C. in a nitrogen atmosphere in a small carbonization furnace. Then, instead of nitrogen, 1 kg / h of steam was heated into the preheated furnace and taken out after heating up to 900 ° C. over 8 hours, and cooled and activated in a nitrogen atmosphere. Activated carbon was obtained. The obtained activated carbon was washed with water for 10 hours and then drained. Then, after drying for 10 hours in an electric dryer maintained at 115 ° C., pulverization was performed for 1 hour by a ball mill to obtain activated carbon 1 as a positive electrode material.

The pore distribution of activated carbon 1 was measured with a pore distribution measuring device (AUTOSORB-1 AS-1-MP) manufactured by Yuasa Ionics. As a result, the BET specific surface area was 2360 m ² / g, the mesopore volume (V1) was 0.52 cc / g, the micropore volume (V2) was 0.88 cc / g, V1 / V2 = 0.59, and the average pore diameter was It was 22.9 kg. Using this activated carbon as a positive electrode active material, 83.4 parts by weight of activated carbon, 8.3 parts by weight of acetylene black, 8.3 parts by weight of PVDF (polyvinylidene fluoride) and NMP (N-methylpyrrolidone) are mixed, Obtained. Next, the obtained slurry was applied to one side of an aluminum foil having a thickness of 15 μm, dried and pressed to obtain a positive electrode having a positive electrode active material layer thickness of 60 μm.

(Assembly and performance evaluation of storage element)
The positive electrode obtained above was cut out to 2.5 cm ² , and this positive electrode and the negative electrode pre-doped with the above lithium ions were opposed to each other with a cellulose paper separator having a thickness of 30 μm interposed therebetween, and a laminate using polypropylene and aluminum. A non-aqueous lithium storage element was assembled by enclosing it in a film exterior. At this time, a solution in which LiPF ₆ was dissolved to a concentration of 1 mol / l in a solvent in which ethylene carbonate and methyl ethyl carbonate were mixed at a volume ratio of 1: 4 was used as an electrolytic solution.
The following evaluation was performed using the lithium ion capacitor cell produced above. The results are shown in Table 2 below.
Charging capacity: 1 mA / 2.0 V constant current-discharging with constant voltage (2 hours), then charging with 1 mA / 4.0 V constant current.
Discharge capacity: Discharge at a constant current of 1 mA / 2.0 V after charging (2 hours) with a constant current of 1 mA / 4.0 V-constant voltage.
Efficiency: Calculated as efficiency (%) = (discharge capacity / charge capacity) × 100.
Output characteristics: Output characteristics (%) = (discharge capacity at 250 mA / 1 discharge capacity at 1 mA) × 100. (The discharge capacity at 250 mA is the capacity when discharged at a constant current of 250 mA / 2.0 V after charging with a constant current of 1 mA / 4.0 V-constant voltage (2 hours).)
Durability test: After the cell was subjected to a float test at 3.8 V and 1000 hr at 50 ° C., the cell was disassembled, the separator film was taken out and washed, and its appearance and air resistance were measured for 5 samples. did. The average value was calculated based on the result.
Presence / absence of short circuit: A cycle test was performed 200 cycles at 25 ° C. with 1 mA / 4.0 V constant current charging and 1 mA / 2.0 V constant current discharging as one cycle. Before this cycle test, charging at a constant current-constant voltage of 1 mA / 4.0 V was performed for 5 hours at five samples, the charging current transition difference at that time was evaluated, and the presence or absence of an initial short circuit was determined from the average value. Similarly, the same work was performed after 200 cycles to determine the presence or absence of short-circuit in long-term stability.

[Example 2]
In a batch paper machine, using a fine cellulose sheet with a basis weight of 7 g / m ² as a guide, in the same manner as in Example 1, a paper slurry prepared by diluting M2 with water was added and papermaking (dehydration) was carried out. Machine (manufactured by Yuri Roll Co., Ltd.), processed in the same manner as in Example 1 except that a heat press treatment at 150 ° C. × 3.1 t / 20 cm was performed, and the film thickness was 11 μm, the porosity was 58%, and the chloride ion-containing concentration Separator S2 which is a white fine cellulose sheet of 16 ppm was obtained.
The structural factor and various physical property values of the separator S2 are shown in Table 1 below.
The lithium ion capacitor performance evaluation using the separator S2 was performed under exactly the same conditions as in Example 1. The results are shown in Table 2 below.

[Example 3, Example 4]
The linter pulp as a raw material is immersed in water so as to be 4% by weight, heat-treated in an autoclave at 130 ° C. for 4 hours, and the resulting swollen pulp is washed with water many times and swollen in a state impregnated with water. Pulp was obtained and the beating process was continued until the CSF value reached 200 ml ↑ in the same manner as in Example 1, followed by 5 times of refining at an operating pressure of 100 MPa using a high-pressure homogenizer, and the solid content concentration was 1.5 wt%. An aqueous dispersion M3 was obtained. Subsequently, the aqueous dispersion M2 and the aqueous dispersion M3 are mixed so that the solid content weight composition is M2 solid content: M3 solid content = 95: 5, and the solid content concentration is 0.1% by weight, and diluted with water. , Dispersed in a blender, and made in the same manner as in Example 1, using a fine cellulose sheet with a basis weight of 10 g / m ² and a basis weight of 13 g / m ² as a guide, and a film thickness of 15 μm and a porosity of 58% (a basis weight of 10 g / m ² and S3), separators S3 and S4, which are two types of white fine cellulose sheets having a film thickness of 21 μm and a porosity of 61% (weight per unit area 13 g / m ² , S4), were obtained (respectively, Example 3 and implementation) Example 4). The chlorine ion-containing concentrations of S3 and S4 were both 16 ppm.
Table 1 below shows the results of the structural factors and various physical properties of the separators S3 and S4.
The lithium ion capacitor performance evaluation using the separators S3 and S4 was performed under exactly the same conditions as in Example 1. The results are shown in Table 2 below.

[Example 5]
Abaca pulp as a raw material is immersed in water so as to be 4% by weight, heat treated in an autoclave at 130 ° C. for 4 hours, and the resulting swollen pulp is washed with water many times and the swollen pulp impregnated with water In the same manner as in Example 1, the beating process is continued until the CSF value becomes 500 ml ↑, and then the micronization process is performed five times at an operating pressure of 100 MPa using a high-pressure homogenizer, and the solid content concentration is 1.5 wt%. An aqueous dispersion M4 was obtained. Subsequently, the aqueous dispersion M2 and the aqueous dispersion M4 are mixed so that the solid content weight composition is M2 solid content: M4 solid content = 95: 5, and the solid content concentration is 0.1% by weight, and diluted with water. , Dispersed in a blender, and made in the same manner as in Example 1, using a fine cellulose sheet with a basis weight of 10 g / m ² as a guide, and a white fine cellulose sheet with a film thickness of 16 μm, a porosity of 60%, and a chlorine ion-containing concentration of 18 ppm A separator S5 was obtained.
The structural factor and various physical property values of the separator S5 are shown in Table 1 below.
The lithium ion capacitor performance evaluation using the separator S5 was performed under exactly the same conditions as in Example 1. The results are shown in Table 2 below.

[Example 6]
After diluting the aqueous dispersion M2 of fine cellulose fibers (solid content concentration: 1.5% by weight) to a solid content concentration of 0.1% by weight, the diluted aqueous dispersion is stirred with a three-one motor to obtain a cationic block type After adding 3% by weight of an aqueous dispersion of functional isocyanate (trade name “Meikanate WEB” (manufactured by Meisei Chemical Co., Ltd.) to a solid content concentration of 1.0% by weight) with respect to the solid cellulose fiber solids weight, After further dispersion for 2 minutes, paper making (dehydration) and drying were carried out in the same manner as in Example 1, using a fine cellulose sheet having a basis weight of 10 g / m ² as a guide. Furthermore, the dried sheet is sandwiched between two SUS metal frames (25 cm × 25 cm), fixed with clips, heat-treated at 160 ° C. for 2 minutes with a thermostat, and cross-linked with a reactant derived from polyfunctional isocyanate. A separator S6, which is a white fine cellulose sheet having a film thickness of 17 μm, a porosity of 63%, and a chlorine ion-containing concentration of 17 ppm, was obtained in the same manner as in Example 1.
The structure factor and various physical property values of the separator S6 are shown in Table 1 below.
The lithium ion capacitor performance evaluation using the separator S6 was performed under exactly the same conditions as in Example 1. The results are shown in Table 2 below.

[Example 7]
In a commercially available aqueous dispersion of epoxy thermosetting resin (solid content concentration 20% by weight), α-alumina powder (average particle size: 0.9 μm), and distilled water, the composition was changed to epoxy thermosetting resin / α. -The coating solution was adjusted so that alumina / water = 1/20/79. Then, the said coating liquid was apply | coated to single side | surface so that epoxy-type thermosetting resin / alpha-alumina basis weight might be 4 g / m < ² > by the gravure roll method to separator S1 produced in Example 1. FIG. This is a white fine cellulose sheet having a film thickness of 20 μm, a porosity of 56%, and a chlorine ion-containing concentration of 45 ppm by subjecting this to heat treatment at 160 ° C. for 10 minutes with a thermostat to cure the epoxy thermosetting resin. Separator S7 was obtained.
The structural factor and various physical property values of the separator S7 are shown in Table 1 below.
The lithium ion capacitor performance evaluation using the separator S7 was performed under exactly the same conditions as in Example 1. The results are shown in Table 2 below.

[Example 8]
After treating the separator S1 produced in Example 1 by the gravure roll method in the same manner as in Example 6 except that the epoxy thermosetting resin / α-alumina basis weight is 3 g / m ^2. Further, to the back side, the above coating liquid was treated in the same manner as in Example 6 except that the epoxy-based thermosetting resin / α-alumina basis weight was 3 g / m ² by the gravure roll method. Separator S8, which is a white sheet molded body having a film thickness of 22 μm, a porosity of 54%, and a chlorine ion-containing concentration of 56 ppm, each of which was laminated with epoxy thermosetting resin / α-alumina basis weight of 3 g / m ² , was obtained.
Table 1 below shows the results of the structure factor and various physical properties of the separator S8.
The lithium ion capacitor performance evaluation using the separator S8 was performed under exactly the same conditions as in Example 1. The results are shown in Table 2 below.

[Comparative Example 1]
In a batch paper machine, using a fine cellulose sheet with a basis weight of 15 g / m ² as a guide, in the same manner as in Example 1, the paper slurry was prepared by diluting from M2 with water, and papermaking (dehydration) was carried out. Machine (manufactured by Yuri Roll Co., Ltd.), except that a hot press treatment at 150 ° C. × 3.1 t / 20 cm was carried out in the same manner as in Example 1, with a film thickness of 23 μm, a porosity of 59%, and a chloride ion-containing concentration Separator R1 which is a white fine cellulose sheet of 22 ppm was obtained.
The structural factor and various physical property values of the separator R1 are shown in Table 1 below.
The lithium ion capacitor performance evaluation using the separator R1 was performed under exactly the same conditions as in Example 1. The results are shown in Table 2 below.

[Comparative Example 2]
In a batch paper machine, using a fine cellulose sheet with a basis weight of 4 g / m ² as a guide, in the same manner as in Example 1, the paper slurry was prepared by diluting from M2 with water and adjusted to make paper (dehydration). Treatment (manufactured by Yuri Roll Co., Ltd.), treatment as in Example 1 except that a heat press treatment at 150 ° C. × 3.1 t / 20 cm was performed, film thickness 6 μm, porosity 58%, chloride ion concentration 21 ppm Separator R2 which is a white fine cellulose sheet was obtained.
The structural factor and various physical property values of the separator R2 are shown in Table 1 below.
Lithium ion capacitor performance evaluation using the separator R2 was performed under exactly the same conditions as in Example 1. The results are shown in Table 2 below.

[Comparative Example 3]
When the aqueous dispersion M3 prepared in Example 3 was used as a raw material and diluted with water to a solid concentration of 0.2% by weight as a papermaking dispersion, 1-hexanol and hydroxypropylmethylcellulose (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: 60SH-4000) was added in an amount of 1.2% by weight (3.9 g) and 0.012% by weight (0.039 g), respectively, and the resulting composition was emulsified and dispersed in a blender for 4 minutes. In the subsequent steps, the same treatment as in Example 1 was performed to obtain a separator R3, which is a white fine cellulose sheet having a film thickness of 14 μm, a porosity of 55%, and a chlorine ion-containing concentration of 16 ppm.
The structure factor and various physical property values of the separator R3 are shown in Table 1 below.
The lithium ion capacitor performance evaluation using the separator R3 was performed under exactly the same conditions as in Example 1. The results are shown in Table 2 below.

[Comparative Example 4]
In a batch paper machine, using a fine cellulose sheet with a basis weight of 10 g / m ² as a guide, in the same manner as in Example 1, a paper slurry prepared by diluting with M1 from water was added and papermaking (dehydration) was carried out. Machine (manufactured by Yuri Roll Co., Ltd.), except that a hot press treatment at 150 ° C. × 3.6 t / 20 cm is carried out in the same manner as in Example 1, with a film thickness of 16 μm, a porosity of 59%, and a chloride ion-containing concentration Separator R4 which is a white fine cellulose sheet of 17 ppm was obtained.
The structural factor and various physical property values of the separator R4 are shown in Table 1 below.
The lithium ion capacitor performance evaluation using the separator R4 was performed under exactly the same conditions as in Example 1. The results are shown in Table 2 below.

[Examples 9 to 16, Comparative Examples 5 to 8]
(Preparation of negative electrode)
The pore distribution was measured using a commercially available coconut shell activated carbon with a pore distribution measuring device (AUTOSORB-1 AS-1-MP) manufactured by Yuasa Ionics Co., Ltd. using nitrogen as an adsorbate. The specific surface area was determined by the BET single point method. Further, as described above, using the isotherm on the desorption side, the mesopore amount was determined by the BJH method, and the micropore amount was determined by the MP method. As a result, the BET specific surface area was 1,780 m ² / g, the mesopore volume (V1) was 0.198 cc / g, the micropore volume (V2) was 0.695 cc / g, V1 / V2 = 0.29, the average fineness. The pore diameter was 21.2 mm. 150 g of this activated carbon is placed in a stainless steel mesh basket, placed on a stainless steel bat containing 150 g of coal-based pitch (softening point: 90 ° C.), and placed in an electric furnace (effective size in the furnace 300 mm × 300 mm × 300 mm). It was installed and a thermal reaction was performed. The heat treatment was performed in a nitrogen atmosphere by raising the temperature to 630 ° C. in 2 hours, holding the same temperature for 4 hours, subsequently cooling to 60 ° C. by natural cooling, and then removing from the furnace to form a composite porous material 2 that becomes a negative electrode material Got.

The composite porous material 2 has a weight ratio of the deposited carbonaceous material to activated carbon of 38%, a BET specific surface area of 434 m ² / g, a mesopore volume (Vm1) of 0.220 cc / g, and a micropore volume (Vm2). ) Was 0.149 cc / g. Furthermore, it was 2.88 micrometers as a result of measuring an average particle diameter using the Shimadzu Corporation laser diffraction type particle size distribution analyzer (SALD-2000J).
Next, 83.4 parts by weight of the composite porous material 2 obtained above, 8.3 parts by weight of acetylene black, 8.3 parts by weight of PVDF (polyvinylidene fluoride) and NMP (N-methylpyrrolidone) are mixed. To obtain a slurry. Next, the obtained slurry was applied to one side of a 15 μm thick copper foil, dried and pressed to obtain a negative electrode having a negative electrode active material layer thickness of 32 μm.
The negative electrode obtained above was cut out to 3 cm ^2, and a total of 1460 mAh / g of lithium ions was pre-doped with respect to the weight of the composite porous material 2, so that Examples 9 to 16 and Comparative Examples 5 to 8 A negative electrode was produced.

(Preparation of positive electrode)
The phenol resin was carbonized in a firing furnace at 600 ° C. for 2 hours in a nitrogen atmosphere. Thereafter, the fired product was pulverized with a ball mill and classified to obtain a carbide having an average particle size of 7 μm.
This carbide and KOH were mixed at a weight ratio of 1: 5, and the mixture was activated in a firing furnace by heating at 800 ° C. for 1 hour in a nitrogen atmosphere. Thereafter, the mixture was stirred and washed with dilute hydrochloric acid adjusted to 2 mol / L for 1 hour, then boiled and washed with distilled water until it became stable between pH 5 and 6, and dried to produce activated carbon 2.
The activated carbon 2 was obtained by a pore distribution measuring device (AUTOSORB-1 AS-1-MP) manufactured by Yuasa Ionics Co., Ltd., and the pore distribution was determined by the above-described method, and the BET specific surface area was determined by the BET one-point method. As a result, the mesopore volume V1 was 1.50 cc / g, the micropore volume V2 was 2.28 cc / g, and the BET specific surface area was 3627 m ² / g.
Using this activated carbon 2 as a positive electrode active material, 83.4 parts by mass of activated carbon, 8.3 parts by mass of conductive carbon black (Lion Corporation Ketjen Black ECP600JD) and PVDF (polyvinylidene fluoride, Kureha KF Polymer W # 9300) 8.3 parts by mass of mp 163 ° C.) was mixed with NMP (N-methylpyrrolidone) to obtain a slurry-like active material layer. Next, the obtained active material layer was applied to one side of an aluminum foil having a thickness of 15 μm and dried. The bulk density of the electrode active material layer was 0.28 g / cm ³ . The bulk density of the electrode active material layer is determined by the weight of the electrode excluding the current collector and the thickness of the current collector in a dry room where the dew point was controlled at -60 ° C. or lower. The thickness of the removed electrode active material layer was determined and calculated. Ono Sokki DG-4120 was used for the measurement of thickness.

The electrode coated with the active material layer is placed at the unwinding roll position in FIG. 1 and heated for the first time at a linear pressure of 110 kgf / cm in a heated press roll apparatus (MSC-31 manufactured by Yuri Roll Co., Ltd.) heated to 140 ° C. The distance between the rolls was 60 μm, and the pressure was applied at 30 μm for the second time to obtain a positive electrode having a bulk density of 0.46 g / cm ^{3 of} the electrode active material layer and a thickness of 67 μm of the positive electrode active material layer. The pressing speed was 5 m / min. The temperature of the heating roll was measured by detecting the roll surface temperature in a non-contact manner with an infrared radiation thermometer IT2-60 manufactured by KEYENCE, and adjusting the temperature to the set temperature by PID control. The linear pressure was calculated from the pressure applied to the pressure roll and the length of contact between the upper and lower rolls.
The positive electrode produced from the activated carbon 2 was cut out to 2.5 cm ² , and this positive electrode and the negative electrode obtained by pre-doping lithium ions into the composite porous material 2 were used to form separators S1 to S8, respectively, in Examples 9 to 16 and the separators R1 to R4 were used in Comparative Examples 5 to 8, respectively, and the production and performance evaluation of lithium ion capacitors were performed in the same manner as in Example 1. The results are shown in Table 2 below.

  The lithium ion capacitor according to the present invention can be used in combination with an internal combustion engine, a fuel cell, or a motor, for example, in the field of a hybrid drive system of an automobile, and is suitable for, for example, an assist application at an instantaneous power peak. Is available.

Claims (14)

A negative electrode body in which a negative electrode active material layer containing a carbon material as a negative electrode active material is disposed on a negative electrode current collector;
A positive electrode body in which a positive electrode active material layer including a positive electrode active material made of either a carbon material or a carbon compound material is disposed on a positive electrode current collector;
A non-aqueous electrolyte containing a lithium ion-containing electrolyte;
A lithium ion capacitor that is housed in an exterior body,
The separator is composed of a single layer containing at least one cellulose fine fiber layer containing regenerated cellulose fine fibers at 70% by weight or more, or a plurality of layers of 3 layers or less, and the following requirements:
(1) The specific surface area equivalent fiber diameter of the fibers constituting the cellulose fine fiber layer is 0.20 μm or more and 0.45 μm or less;
(2) Air permeability resistance is 5 s / 100 ml or more and 40 s / 100 ml or less; and (3) Film thickness is 8 μm or more and 22 μm or less;
The lithium ion capacitor characterized by being a separator satisfying the following. ^2. The lithium ion capacitor according to claim 1, wherein a basis weight of the cellulose fine fiber layer is 4 g / m ² or more and 13 g / m ² or less.   The lithium ion capacitor according to claim 1 or 2, wherein a fiber diameter corresponding to a specific surface area of the regenerated cellulose fine fiber is 0.20 µm or more and 0.45 µm or less.   The lithium ion capacitor according to any one of claims 1 to 3, wherein the cellulose fine fiber layer contains natural cellulose fine fibers in an amount of less than 30% by weight.   The lithium ion capacitor according to any one of claims 1 to 4, wherein the cellulose fine fiber layer contains natural cellulose fine fibers that are fine fibers having a CSF of 300 ml ↑ or more in an amount of less than 30% by weight.   The lithium ion capacitor of any one of Claims 1-3 in which the fine fiber which consists of organic polymers other than a cellulose is contained in the said cellulose fine fiber layer at less than 30 weight%.   The lithium ion capacitor of any one of Claims 1-6 in which the said cellulose fine fiber layer contains a reactive crosslinking agent by 10 weight% or less. One layer of the three layers following multilayer structure comprises a substrate layer is a basis weight 3 g / m ² or more 15 g / m ² or less of the nonwoven fabric or paper, a lithium ion capacitor according to any one of claims 1 to 7.   The lithium ion capacitor according to claim 1, wherein an insulating porous film is formed on one side or both sides of the separator. The lithium ion capacitor according to claim 9, wherein the insulating porous film includes an inorganic filler and a resin binder and has a basis weight of 2 g / m ² or more and 10 g / m ² or less.   The negative electrode active material is a composite porous material in which the surface of activated carbon is coated with a carbon material, and the amount of mesopores derived from pores having a diameter of 20 mm or more and 500 mm or less calculated by the BJH method is Vm1 (cc / g ), When the amount of micropores derived from pores having a diameter of less than 20 mm calculated by the MP method is Vm2 (cc / g), 0.010 ≦ Vm1 ≦ 0.250, 0.001 ≦ Vm2 ≦ 0.200, And the lithium ion capacitor according to claim 1, wherein 1.5 ≦ Vm1 / Vm2 ≦ 20.0 is satisfied.   The negative electrode active material is a composite porous material in which the surface of activated carbon is coated with a carbonaceous material, and lithium ions of 1,050 mAh / g or more and 2,050 mAh / g or less per unit mass of the composite porous material 2 is pre-doped, the mass ratio of the carbonaceous material to the activated carbon is 10% or more and 60% or less, and the thickness of the negative electrode active material layer is 20 μm or more and 45 μm or less per side. 10. The lithium ion capacitor according to any one of 10 to 10. The positive electrode active material has a mesopore amount derived from pores having a diameter of 20 to 500 mm calculated by the BJH method as V1 (cc / g), and a micropore amount derived from pores having a diameter of less than 20 mm calculated by the MP method. Is V2 (cc / g), 0.3 <V1 ≦ 0.8 and 0.5 ≦ V2 ≦ 1.0 are satisfied, and the specific surface area measured by the BET method is 1,500 m ² / The lithium ion capacitor of any one of Claims 1-12 which is activated carbon which shows g or more and 3000 m < ² > / g or less. The positive electrode active material has a mesopore volume V1 (cc / g) derived from pores having a diameter of 20 mm or more and 500 mm or less calculated by the BJH method satisfying 0.8 <V1 ≦ 2.5, and a diameter calculated by the MP method. The amount of micropores V2 (cc / g) derived from pores less than 20 mm satisfies 0.8 <V2 ≦ 3.0, and the specific surface area measured by the BET method is 3,000 m ² / g or more 4, The lithium ion capacitor of any one of Claims 1-12 which is activated carbon which shows 000 m < ² > / g or less.