JP2009205918A - Power storage device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power storage device capable of realizing at the same time an energy density and high output characteristics, low environmental load, and high safety. <P>SOLUTION: The power storage device consists of a positive electrode 1, a negative electrode 2, and a separator 4 including an electrolyte to separate these electrodes. The positive electrode 1 includes a nitroxyl compound which has a nitroxyl cation partial structure as shown in formula (1) in oxidation state and has a nitroxyl radical partial structure as shown in a formula (2) in reduction state, and an active carbon particle, and the negative electrode 2 includes a substance capable of carrying lithium ions reversibly, and the electrolyte is an aprotic organic solvent that includes lithium salt. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electricity storage device including a positive electrode, a negative electrode, and a separator disposed therebetween.

  As global warming and environmental problems become more serious, electric vehicles or hybrid electric vehicles are being actively developed as clean vehicles to replace gasoline vehicles. Power storage devices used for such applications are required to achieve both high energy density and high output characteristics, and at the same time, are required to have durability exceeding 10 years, high safety, and the like.

  In order to achieve both high energy density and high power density, it is effective to increase the operating voltage. Therefore, for these electricity storage devices, an electrolytic solution including a negative electrode containing a substance capable of reversibly carrying lithium ions and an aprotic organic solvent containing a lithium salt is used.

  As a typical positive electrode material used for these electricity storage devices, a transition metal oxide can be given. This power storage device is called a lithium ion secondary battery and is characterized by a very high energy density. In recent years, output characteristics have also been improved, and compatibility with high energy density has been realized. However, there are still problems such as a decrease in safety due to thermal runaway, a price increase due to resource shortage, a problem of environmental burden, and the like, and it has not been put into practical use for automobiles.

  Another positive electrode material that can be used as a transition metal oxide is activated carbon. These power storage devices using activated carbon for the positive electrode are called lithium ion capacitors. Since electric charges are stored by an electrostatic mechanism using an electric double layer, the energy density is small but the output density is high and the cycle stability is also high. There are no resource and safety issues like transition metal oxides. However, since the energy density is too low, it is difficult to balance the capacity with the negative electrode, and a technique for pre-doping lithium ions to the negative electrode by a chemical method or an electrochemical method is required. (For example, see Patent Document 1)

  In recent years, a method of pre-doping relatively easily has been proposed by providing a hole penetrating the front and back surfaces for each of the positive electrode current collector and the negative electrode current collector, and the practicality of lithium ion capacitors has greatly increased. This is because lithium ions can move between the front and back of the electrode through the through-hole without being blocked by the electrode current collector. (For example, see Patent Document 2)

  As another positive electrode material, a nitroxyl compound that has an oxoammonium cation partial structure in an oxidized state and a nitroxyl radical partial structure in a reduced state has been proposed. This power storage device is called an organic radical secondary battery, and has a performance located between a lithium ion secondary battery and a lithium ion capacitor. (For example, see Patent Document 3)

However, this organic radical secondary battery has a problem in that a large amount of a conductivity-imparting agent must be mixed in the electrode in order to achieve a high output density because the nitroxyl compound itself has poor electronic conductivity. If a large amount of a conductivity-imparting agent is mixed in the electrode, the energy density is lowered. As a result, it is difficult to achieve both a high energy density and a high output density.
JP 2002-185565 A Japanese Patent Laid-Open No. 2-29595 JP 2002-304996 A JP 2005-228705 A

  The present invention provides an energy storage device including an aprotic organic solvent electrolyte in which a lithium salt is dissolved, such as a lithium ion secondary battery, a lithium ion capacitor, and an organic radical secondary battery. It is an object to provide an electricity storage device that can simultaneously realize low environmental load and high safety.

The present invention is an electricity storage device comprising a positive electrode, a negative electrode, and a separator including an electrolyte disposed therebetween, wherein the positive electrode has a nitroxyl cation partial structure represented by formula (I) in an oxidized state, and is reduced A non-nitrogen compound containing a nitroxyl compound represented by formula (II) having a nitroxyl radical partial structure and activated carbon particles, the negative electrode containing a substance capable of reversibly supporting lithium ions, and the electrolyte containing a lithium salt. An electricity storage device, which is a protic organic solvent.

  ADVANTAGE OF THE INVENTION According to this invention, the electrical storage device which implement | achieved the high energy density and the high output characteristic, the low environmental load, and high safety | security simultaneously can be provided. In order to achieve both high energy density and power density, it is effective to increase the operating voltage of the electricity storage device. Therefore, in the electricity storage device of the present invention, an electrolytic solution including a negative electrode containing a substance capable of reversibly supporting lithium ions and an aprotic organic solvent containing a lithium salt is used.

  Furthermore, in the electricity storage device according to the present invention, a nitroxyl compound is used as the positive electrode material in consideration of safety and reduction of environmental load. Further, in order to increase the output density, not the conductivity imparting agent but activated carbon is mixed. As a result, it is possible to provide a power storage device that simultaneously achieves high energy density, high output characteristics, low environmental load, and high safety.

  According to the electricity storage device of the present invention, high energy density, high output characteristics, low environmental load, and high safety can be realized at the same time.

  Hereinafter, the electrical storage device of this embodiment is demonstrated using drawing. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate.

  The electricity storage device in this embodiment will be described. FIG. 1 is a cross-sectional view of an electricity storage device.

  The basic configuration of the electricity storage device in the present embodiment is that a positive electrode 1 containing both a nitroxyl compound and activated carbon, a positive electrode current collector 1A connected to the positive electrode 1, and a positive electrode current collector 1A connected to energy outside the cell. A positive electrode lead 1B to be taken out, a negative electrode 2 containing a substance capable of reversibly carrying lithium ions, a negative electrode current collector 2A connected to the negative electrode 2, and a negative electrode current collector 2A connected to the energy outside the cell A negative electrode lead 2B to be taken out, a lithium supply source 3 for pre-doping the negative electrode 2, a lithium supply source current collector 3A connected to the lithium supply source 3, and the positive electrode 1 and the negative electrode 2 are interposed between them to conduct electrons It consists of the separator 4 which conducts only ions without conducting, and the exterior body 5 which seals them.

  However, the shape of the electricity storage device in the present embodiment is not particularly limited. A cylindrical shape, a square shape, or the like can be appropriately selected depending on the application. The number of electrode layers may be a single layer or a plurality of layers. Further, when there are a plurality of layers, the stacking method or the winding method may be used.

The positive electrode 1 in this embodiment contains a nitroxyl compound and activated carbon at the same time. The nitroxyl compound in the present embodiment is a compound having, as partial structures, a nitroxide radical represented by formula (I) in the reduced state and an oxoammonium (nitroxide cation) represented by formula (II) in the oxidized state.

From the viewpoint of long-term stability, the nitroxyl compound is 2,2,6,6-tetramethylpiperidinoxyl cation represented by the formula (1) and 2,2,6 represented by the formula (2) in an oxidized state. It is preferably one nitroxyl compound selected from the group consisting of a 5,5-tetramethylpyrrolidinoxyl cation and a 2,2,5,5-tetramethylpyrrolinoxyl cation represented by the formula (3).

  The main function of the nitroxyl compound in the positive electrode 1 is a role as an active material contributing to power storage. Therefore, as the proportion of the nitroxyl compound contained in the positive electrode 1 is increased, the energy density is improved. However, since the nitroxyl compound itself has poor conductivity, the output density decreases as the ratio of the nitroxyl compound contained in the positive electrode 1 increases. The ratio of the nitroxyl compound contained in the positive electrode 1 is not particularly limited. If it is 1% by weight or more in the positive electrode 1, it is effective, and if it is 10% by weight or more, a sufficient effect is seen. Furthermore, when it is desired to obtain a power storage effect as large as possible, it is preferably 30% by weight or more, particularly 50% by weight or more.

  The activated carbon in the present embodiment is amorphous charcoal having a strong adsorptivity and mostly composed of carbonaceous matter. Usually, raw materials such as phenol resin, petroleum pitch, petroleum coke, coconut husk, or coal-based coke are calcined in an inert gas atmosphere such as nitrogen gas or argon gas, and the resulting material is steamed or alkali activated. It is obtained by the method of using and activating. Although it does not restrict | limit especially about the raw material of the activated carbon in this embodiment, In order to obtain sufficient specific surface area, it is preferable that they are a phenol resin type activated carbon, a petroleum pitch type activated carbon, a petroleum coke type activated carbon, or a coal coke type activated carbon.

The particle diameter of the activated carbon in the present embodiment is not particularly limited, but usually, pulverized and pulverized powder is used. For example, the 50% volume cumulative diameter (also referred to as D50) is 2 μm or more, preferably 2 to ₅₀ μm, and most preferably 2 to 20 μm. Moreover, it is preferable that the average pore diameter of the activated carbon in this embodiment is 10 nm or less.
In the present embodiment, the average particle size is D ₅₀ value of the particle size distribution was measured with a laser diffraction type particle size distribution measuring apparatus.

When the activated carbon in the present embodiment is used as a conductive auxiliary agent for the positive electrode active material (nitroxyl radical), activated carbon having a small surface area (500 to 1000 m ² // in order to suppress side reactions and ensure sufficient conductivity. g) is often used. However, the present invention has found that the use of activated carbon having a large surface area (1000 m ² / g or more) can improve the capacity of the electricity storage device. On the other hand, when the surface area is not sufficiently large (1500 m ² / g or less), it has also been found that the effect of improving the capacity is relatively small.

On the other hand, if the surface area is too large (2500 m ² / g), side reactions may occur and the performance may be deteriorated, or the output characteristics may be deteriorated due to insufficient conductivity.

Therefore, the specific surface area of the activated carbon in the present embodiment, 1000 m ² / g or more, preferably 1000~3000m ² / g, more preferably 1500~2500m ² / g.

  The main functions of the activated carbon in the positive electrode 1 are a role as an active material that contributes to capacity and a role as a conductive auxiliary agent that supplies electrons to the nitroxyl compound. Depending on the type of material, the capacity of the activated carbon is smaller than the capacity of the nitroxyl compound. In the voltage range of 2.5 to 4.2 V, it is about 1/2 to 1/10 of the nitroxyl compound. Therefore, as the ratio of the activated carbon to the nitroxyl compound is increased, the energy density is decreased, but the output density is improved.

  The proportion of the activated carbon contained in the positive electrode 1 is preferably 10% by weight or more in order to obtain a sufficient capacity when the positive electrode 1 is 100% by weight. On the other hand, in order to contain a sufficient amount of nitroxyl radicals and reduce the internal resistance, it is preferably 90% by weight or less, and more preferably 75% by weight or less.

  Therefore, the activated carbon contained in the positive electrode 1 in the present embodiment acts as a conductive auxiliary agent for the nitroxyl radical, and at the same time, from the viewpoint of operating as an active material, it is in the range of 10 to 90% by weight in the positive electrode 1. It is preferably 10 to 75% by weight.

  The positive electrode 1 in this embodiment may further contain a conductive additive, a binder, and the like. Examples of the conductive auxiliary agent include carbon materials such as carbon black, acetylene black, and carbon fiber, and conductive polymers such as polyacetylene, polyphenylene, polyaniline, and polypyrrole. Examples of the binder include resins such as polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-hexafluoropropylene copolymer, styrene-butadiene copolymer rubber, polypropylene, polyethylene, and polyimide.

  Examples of the material of the positive electrode current collector 1A include aluminum, an aluminum alloy, and stainless steel. As the shape, a foil, a flat plate, or a mesh can be used. In particular, when pre-doping lithium ions to the negative electrode 2, those having holes penetrating the front and back surfaces are preferable. A foil etc. can be mentioned.

  The shape, number, etc. of the through holes of the positive electrode current collector 1A are such that lithium ions in the electrolyte described later can move between the front and back of the electrode without being blocked by the positive electrode current collector 1A. Therefore, it can be set appropriately so as to be easily closed. Examples of the material of the positive electrode lead 1B include aluminum, an aluminum alloy, and stainless steel. As the shape, a foil, a flat plate, or a mesh can be used.

  The negative electrode 2 in the present embodiment includes a substance capable of reversibly supporting lithium ions. Specifically, carbon materials such as graphite, hard carbon and activated carbon, conductive polymers such as polyacene, polyacetylene, polyphenylene, polyaniline and polypyrrole, lithium alloys such as lithium aluminum alloy, lithium oxides such as lithium titanate And lithium metal. Further, the negative electrode 2 in the present embodiment may include a conductivity imparting agent or a binder.

  Examples of the conductivity-imparting agent include carbon materials such as carbon black, acetylene black, and carbon fiber, and metal powder. Examples of the binder include polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-hexafluoropropylene copolymer, styrene-butadiene copolymer rubber, polypropylene, polyethylene, and polyimide.

  Examples of the material of the negative electrode current collector 2A include copper, nickel, and stainless steel. As the shape, a foil, a flat plate, or a mesh can be used. In particular, when pre-doping lithium ions to the negative electrode 2, those having holes penetrating the front and back surfaces are preferable. A foil etc. can be mentioned.

  The shape and number of through-holes of the negative electrode current collector 2A are such that lithium ions in the electrolyte described later can move between the front and back of the electrode without being blocked by the negative electrode current collector 2A. Therefore, it can be set appropriately so as to be easily closed. Examples of the material of the negative electrode lead 2B include copper, nickel, and stainless steel. As the shape, a foil, a flat plate, or a mesh can be used.

  The lithium supply source 3 in this embodiment serves as a supply source for pre-doping lithium ions to the negative electrode 2. Examples of the material include lithium metal and lithium aluminum alloy, and lithium is particularly preferable. When the ratio of the nitroxyl compound contained in the positive electrode 1 is high and the capacity of the positive electrode 1 is sufficiently large, there is no need for pre-doping treatment, and therefore the lithium supply source 3 and the lithium supply source current collector 3A may be removed. Absent. Examples of the material of the lithium supply source current collector 3A include copper, nickel, and stainless steel. As the shape, a foil, a flat plate, or a mesh can be used.

The separator 4 in this embodiment is interposed between the positive electrode 1 and the negative electrode 2 and plays a role of conducting only ions without conducting electrons. The separator 4 in the present embodiment is not particularly limited, and a conventionally known separator can be used. Examples thereof include polyolefins such as polypropylene and polyethylene, and porous films such as fluororesin. In the present embodiment, the separator 4 holds an aprotic organic solvent electrolyte containing a lithium salt and conducts ions. The aprotic organic solvent electrolyte containing a lithium salt desirably has an ionic conductivity of 10 ⁻⁵ to 10 ⁻¹ S / cm at room temperature.

Examples of the lithium salt in the present embodiment include LiPF ₆ , LiClO ₄ , LiBF ₄ , LiSbF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiB (C ₂ O ₄ ) _2. Etc. In addition, examples of the aprotic organic solvent in this embodiment include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), and vinylene carbonate (VC), dimethyl carbonate (DMC), and diethyl carbonate. (DEC), chain carbonates such as ethyl methyl carbonate (EMC) and dipropyl carbonate (DPC), aliphatic carboxylic acid esters such as methyl formate, methyl acetate and ethyl propionate, lactones such as γ-butyrolactone, Chain ethers such as ethoxyethane (DEE) and ethoxymethoxyethane (EME), cyclic ethers such as tetrahydrofuran and methyltetrahydrofuran, 1-ethyl-3-methylimidazolium TFSI, N-butyl-N-methyl Ionic liquids and the like, such as pyrrolidinium TFSI and the like. These aprotic organic solvents may be used individually by 1 type, or may mix 2 or more types. Although it does not restrict | limit especially as a density | concentration of the lithium salt with respect to an aprotic organic solvent, From a viewpoint of showing sufficient ionic conductivity, it is desirable to exist in the range of 0.4-1.5 mol / L.

  The material of the exterior body 5 in the present embodiment is not particularly limited, and a conventionally known material can be used. For example, a metal material such as iron or aluminum, a plastic material, a glass material, or a composite material obtained by laminating them can be used. However, from the viewpoint of miniaturization of the electricity storage device, the laminate film outer package 5 in which aluminum and a polymer film such as nylon or polypropylene are laminated is preferable.

(Example of manufacturing an electricity storage device)
Next, an example of manufacturing the electricity storage device in this embodiment will be described.

(Synthesis example of nitroxyl compound)
In a 100 ml eggplant flask equipped with a reflux tube, 20 g (0.089 mol) of 2,2,6,6-tetramethylpiperidine methacrylate monomer was placed and dissolved in 80 ml of dry tetrahydrofuran. Thereto, 0.29 g (0.00187 mol) (monomer / AIBN mass ratio = 50/1) of azobisisobutyronitrile (AIBN) was added, and the mixture was stirred at 75 to 80 ° C. in an argon atmosphere. After reacting for 6 hours, it was allowed to cool to room temperature. The polymer was precipitated in hexane, separated by filtration, and dried under reduced pressure to obtain 18 g (yield 90%) of poly (2,2,6,6-tetramethylpiperidine methacrylate). Next, 10 g of the obtained poly (2,2,6,6-tetramethylpiperidine methacrylate) was dissolved in 100 ml of dry-treated dichloromethane. To this, 100 ml of a dichloromethane solution of 15.2 g (0.088 mol) of m-chloroperbenzoic acid was added dropwise over 1 hour with stirring at room temperature. After further stirring for 6 hours, precipitated m-chlorobenzoic acid was removed by filtration, and the filtrate was washed with an aqueous sodium carbonate solution and water, and then dichloromethane was distilled off. The remaining solid was pulverized, and the resulting powder was washed with diethyl carbonate (DEC), dried under reduced pressure, and poly (2,2,6,6-tetramethylpiperidin represented by the following chemical formula (1). Noxy radical methacrylate) (PTMA) (7.2 g) was obtained (yield 68.2%, brown powder). The structure of the obtained polymer was confirmed by IR. Moreover, as a result of measuring by GPC, the value of weight average molecular weight Mw = 89000 and dispersion degree Mw / Mn = 3.30 was obtained.

(Preparation example of positive electrode 1)
The phenol resin was carbonized at 700 ° C. for 2 hours, and then activated by steam at 800 ° C. for 3 hours to obtain activated carbon having a specific surface area of 2000 m ² / g. The activated carbon (1200 mg), the finely divided nitroxyl compound (300 mg), carbon black (1200 mg), carboxymethylcellulose (240 mg), Teflon (R) fine powder (60 mg), and water (24 g) were mixed well to prepare a slurry of the positive electrode 1.

  A 38-micron thick expanded metal aluminum current collector was coated with a carbon conductive paint and dried to obtain a positive electrode current collector. The through hole was almost blocked by the carbon-based conductive paint. The slurry of the positive electrode 1 was applied on the positive electrode current collector 1A and water was sufficiently vaporized, and then stored at 80 ° C. overnight by vacuum drying to produce the positive electrode 1. The total thickness of the positive electrode 1 including the current collector was 140 microns.

(Example of production of negative electrode 2)
13.5 g of graphite powder (particle size 6 microns), 1.35 g of polyvinylidene fluoride, 0.15 g of carbon black, and 30 g of N-methylpyrrolidone solvent were mixed well to prepare a negative electrode slurry. A negative electrode slurry was applied to both surfaces of an expanded metal copper foil having a thickness of 32 μm coated with a carbon-based conductive paint and vacuum-dried to prepare negative electrode 2. The total thickness of the negative electrode 2 including the current collector was 90 microns.

(Example of manufacturing an electricity storage device)
In a dry room having a dew point of −60 ° C. or lower, the positive electrode 1 and the negative electrode 2 were sequentially stacked with the separator 4 interposed therebetween to prepare an electrode laminate. A lithium metal-laminated copper foil serving as the lithium supply source 3 was inserted into the uppermost part of the laminate. The aluminum foil as the positive electrode current collector 1A and the positive electrode lead 1B are ultrasonically welded, and the copper foil as the negative electrode current collector 2A, the copper foil as the lithium source current collector 3A, and the negative electrode lead 2B are similarly welded. did. They were covered with an aluminum laminate film having a thickness of 115 microns, and the three sides including the lead portions were heat-sealed first. Next, a mixed electrolyte solution of EC / DEC = 3/7 containing 1 mol / L LiN (C ₂ F ₅ SO ₂ ) ₂ was inserted into the cell and thoroughly impregnated in the electrode. Finally, the last four sides were thermally fused under reduced pressure to produce an electricity storage device.

<Example 1>
A positive electrode 1 was prepared with a mixing ratio of 10 wt% of a nitroxyl compound (PTMA), 40 wt% of activated carbon (phenol resin raw material, specific surface area 2000 m ² / g), 40 wt% of a conductivity imparting agent, and 10 wt% of a binder (cellulose, Teflon). Therefore, a lithium storage source 3 was inserted to produce an electricity storage device. The thickness of the positive electrode 1 was adjusted to a weight of 10 mg per 1 cm ² . After device fabrication, a conditioning process was performed and the battery was charged to 4 V with a current of 50 mA. Thereafter, discharging was performed at a current of 50 mA, and the capacity up to 3 V was measured. At the same time, after charging the device, discharging was performed at a current corresponding to 10 mA per 1 cm ^{2 of} the electrode, and the voltage value after 2 seconds was measured. As a result, the initial capacity of the cell was 3.40 V after 2 seconds when discharged at 55 mAh and 10 mA / cm ² .
In addition, the specific surface area of activated carbon measured the adsorption / desorption isotherm by the gas adsorption method, and calculated | required by BET method.

<Example 2>
For the pre-doping, the positive electrode 1 was prepared with a mixing ratio of 10 wt% of nitroxyl compound (PTMA), 40 wt% of activated carbon (coconut shell raw material, specific surface area 800 m ² / g), 40 wt% of conductivity imparting agent, and 10 wt% of binder (cellulose, Teflon). The lithium supply source 3 was inserted to produce an electricity storage device. The thickness of the positive electrode 1 was adjusted to a weight of 10 mg per 1 cm ² . After device fabrication, a conditioning process was performed and the battery was charged to 4 V with a current of 50 mA. Thereafter, discharging was performed at a current of 50 mA, and the capacity up to 3 V was measured. At the same time, after charging the device, discharging was performed at a current corresponding to 10 mA per 1 cm ^{2 of} the electrode, and the voltage value after 2 seconds was measured. As a result, the initial capacity of the cell was 3.43 V after 2 seconds when discharged at 38 mAh and 10 mA / cm ² .

<Example 3>
The positive electrode 1 was prepared by mixing a nitroxyl compound (PTMA) 10 wt%, activated carbon (phenol resin raw material, specific surface area 2000 m ² / g) 75 wt%, a conductivity imparting agent 5 wt%, and a binder (cellulose, Teflon) 10 wt%. Therefore, a lithium storage source 3 was inserted to produce an electricity storage device. The thickness of the positive electrode 1 was adjusted to a weight of 10 mg per 1 cm ² . After device fabrication, a conditioning process was performed and the battery was charged to 4 V with a current of 50 mA. Thereafter, discharging was performed at a current of 50 mA, and the capacity up to 3 V was measured. At the same time, after charging the device, discharging was performed at a current corresponding to 10 mA per 1 cm ^{2 of} the electrode, and the voltage value after 2 seconds was measured. As a result, the cell had an initial capacity of 79 mAh and 10 mA / cm ² , and the voltage after 2 seconds was 3.36 V.

<Example 4>
The positive electrode 1 was prepared by mixing a nitroxyl compound (PTMA) 30 wt%, activated carbon (phenol resin raw material, specific surface area 2000 m ² / g) 30 wt%, a conductivity imparting agent 30 wt%, and a binder (cellulose, Teflon) 10 wt%. Therefore, a lithium storage source 3 was inserted to produce an electricity storage device. The thickness of the positive electrode 1 was adjusted to a weight of 10 mg per 1 cm ² . After device fabrication, a conditioning process was performed and the battery was charged to 4 V with a current of 50 mA. Thereafter, discharging was performed at a current of 50 mA, and the capacity up to 3 V was measured. At the same time, after charging the device, discharging was performed at a current corresponding to 10 mA per 1 cm ^{2 of} the electrode, and the voltage value after 2 seconds was measured. As a result, the cell had an initial capacity of 118 mAh and 10 mA / cm ² , and the voltage after 2 seconds was 3.32 V.

<Example 5>
The positive electrode 1 was prepared by mixing a nitroxyl compound (PTMA) 50 wt%, activated carbon (phenol resin raw material, specific surface area 2000 m ² / g) 30 wt%, a conductivity imparting agent 10 wt%, and a binder (cellulose, Teflon) 10 wt%. Therefore, a lithium storage source 3 was inserted to produce an electricity storage device. The thickness of the positive electrode 1 was adjusted to a weight of 10 mg per 1 cm ² . After device fabrication, a conditioning process was performed and the battery was charged to 4 V with a current of 50 mA. Thereafter, discharging was performed at a current of 50 mA, and the capacity up to 3 V was measured. At the same time, after charging the device, discharging was performed at a current corresponding to 10 mA per 1 cm ^{2 of} the electrode, and the voltage value after 2 seconds was measured. As a result, the initial capacity of the cell was 188 mAh, 10 mA / cm ² , and the voltage after 2 seconds was 3.26V.

<Example 6>
The positive electrode 1 was prepared by mixing a nitroxyl compound (PTMA) 50 wt%, activated carbon (phenol resin raw material, specific surface area 2000 m ² / g) 30 wt%, a conductivity imparting agent 10 wt%, and a binder (cellulose, Teflon) 10 wt%. Therefore, an electricity storage device was produced without inserting the lithium supply source 3 for the purpose. The thickness of the positive electrode 1 was adjusted to a weight of 10 mg per 1 cm ² . After device fabrication, a conditioning process was performed and the battery was charged to 4 V with a current of 50 mA. Thereafter, discharging was performed at a current of 50 mA, and the capacity up to 3 V was measured. At the same time, after charging the device, discharging was performed at a current corresponding to 10 mA per 1 cm ^{2 of} the electrode, and the voltage value after 2 seconds was measured. As a result, the initial capacity of the cell was 3.19 V after 2 seconds when discharged at 157 mAh and 10 mA / cm ² .

<Example 7>
The positive electrode 1 was prepared with a mixing ratio of 70% by weight of a nitroxyl compound (PTMA), 15% by weight of activated carbon (phenol resin raw material, specific surface area 2000 m ² / g), 10% by weight of a conductivity imparting agent, and 5% by weight of a binder (cellulose, Teflon). Therefore, an electricity storage device was produced without inserting the lithium supply source 3 for the purpose. The thickness of the positive electrode 1 was adjusted to a weight of 10 mg per 1 cm ² . After device fabrication, a conditioning process was performed and the battery was charged to 4 V with a current of 50 mA. Thereafter, discharging was performed at a current of 50 mA, and the capacity up to 3 V was measured. At the same time, after charging the device, discharging was performed at a current corresponding to 10 mA per 1 cm ^{2 of} the electrode, and the voltage value after 2 seconds was measured. As a result, the cell had an initial capacity of 192 mAh and 10 mA / cm ² , and the voltage after 2 seconds was 3.08 V.

<Comparative Example 1>
A positive electrode 1 was prepared at a mixing ratio of 10 wt% of a nitroxyl compound (PTMA), 80 wt% of a conductivity imparting agent, and 10 wt% of a binder (cellulose, Teflon), and a lithium supply source 3 for pre-doping was inserted to manufacture a power storage device. The thickness of the positive electrode 1 was adjusted to a weight of 10 mg per 1 cm ² . After device fabrication, a conditioning process was performed and the battery was charged to 4 V with a current of 50 mA. Thereafter, discharging was performed at a current of 50 mA, and the capacity up to 3 V was measured. At the same time, after charging the device, discharging was performed at a current corresponding to 10 mA per 1 cm ^{2 of} the electrode, and the voltage value after 2 seconds was measured. As a result, the cell had an initial capacity of 27 mAh and 10 mA / cm ² , and the voltage after 2 seconds was 3.41 V.

<Comparative Example 2>
A positive electrode 1 was prepared with a mixing ratio of 30 wt% of a nitroxyl compound (PTMA), 60 wt% of a conductivity imparting agent, and 10 wt% of a binder (cellulose, Teflon), and a lithium supply source 3 for pre-doping was inserted to prepare an electricity storage device. The thickness of the positive electrode 1 was adjusted to a weight of 10 mg per 1 cm ² . After device fabrication, a conditioning process was performed and the battery was charged to 4 V with a current of 50 mA. Thereafter, discharging was performed at a current of 50 mA, and the capacity up to 3 V was measured. At the same time, after charging the device, discharging was performed at a current corresponding to 10 mA per 1 cm ^{2 of} the electrode, and the voltage value after 2 seconds was measured. As a result, the cell had an initial capacity of 104 mAh and 10 mA / cm ² , and the voltage after 2 seconds was 3.36 V.

<Comparative Example 3>
A positive electrode 1 was prepared at a mixing ratio of 50 wt% of a nitroxyl compound (PTMA), 40 wt% of a conductivity imparting agent, and 10 wt% of a binder (cellulose, Teflon), and a lithium supply source 3 for pre-doping was inserted to manufacture an electricity storage device. The thickness of the positive electrode 1 was adjusted to a weight of 10 mg per 1 cm ² . After device fabrication, a conditioning process was performed and the battery was charged to 4 V with a current of 50 mA. Thereafter, discharging was performed at a current of 50 mA, and the capacity up to 3 V was measured. At the same time, after charging the device, discharging was performed at a current corresponding to 10 mA per 1 cm ^{2 of} the electrode, and the voltage value after 2 seconds was measured. As a result, the initial capacity of the cell was 162 mAh, 10 mA / cm ² , and the voltage after 2 seconds was 3.30 V.

<Comparative example 4>
A positive electrode 1 was prepared with a mixing ratio of 50 wt% of a nitroxyl compound (PTMA), 40 wt% of a conductivity-imparting agent, and 10 wt% of a binder (cellulose, Teflon), and an electricity storage device was manufactured without inserting a lithium supply source 3 for pre-doping. The thickness of the positive electrode 1 was adjusted to a weight of 10 mg per 1 cm ² . After device fabrication, a conditioning process was performed and the battery was charged to 4 V with a current of 50 mA. Thereafter, discharging was performed at a current of 50 mA, and the capacity up to 3 V was measured. At the same time, after charging the device, discharging was performed at a current corresponding to 10 mA per 1 cm ^{2 of} the electrode, and the voltage value after 2 seconds was measured. As a result, the cell had an initial capacity of 140 mAh and 10 mA / cm ² , and the voltage after 2 seconds was 3.25 V.

<Comparative Example 5>
A positive electrode 1 was prepared with a mixing ratio of 70 wt% of a nitroxyl compound (PTMA), 25 wt% of a conductivity imparting agent, and 5 wt% of a binder (cellulose, Teflon), and an electricity storage device was manufactured without inserting the lithium supply source 3 for pre-doping. The thickness of the positive electrode 1 was adjusted to a weight of 10 mg per 1 cm ² . After device fabrication, a conditioning process was performed and the battery was charged to 4 V with a current of 50 mA. Thereafter, discharging was performed at a current of 50 mA, and the capacity up to 3 V was measured. At the same time, after charging the device, discharging was performed at a current corresponding to 10 mA per 1 cm ^{2 of} the electrode, and the voltage value after 2 seconds was measured. As a result, the initial capacity of the cell was 184 mAh and 10 seconds after discharge at 10 mA / cm ² , the voltage after 2 seconds was 3.14V.

  The charge / discharge curves of the electricity storage devices produced in Example 1 and Comparative Example 1 are shown in FIG. Although the capacity of the flat part by the nitroxyl compound does not change, it can be seen that the total capacity is increased by adding activated carbon.

FIG. 3 shows the cell voltage after 2 seconds when the electricity storage devices produced in Example 1 and Comparative Example 1 were discharged at 1, ² , 3, 5, 10 mA / cm ² , respectively. When the current is increased, the cell voltage tends to decrease due to the direct current resistance of the electricity storage device. However, there was no significant difference between Example 1 and Comparative Example 1. In this composition, it was confirmed that the DC resistance did not increase even when a part of the conductivity-imparting agent was replaced with activated carbon.

Table 1 below summarizes the composition of the positive electrode 1 used in each example and comparative example, the presence or absence of the lithium supply source 3, the initial capacity of the obtained cell, and the voltage after 2 seconds when discharged at 10 mA / cm ^2. .
When Example 1 and Comparative Example 1 were compared, it was found that the capacity of the electricity storage device could be increased without increasing the direct current resistance by replacing part of the conductivity-imparting agent with activated carbon. Further, comparing Example 1 and Example 2, it was found that the activated carbon of the phenol resin raw material having a large specific surface area of the activated carbon had a larger capacity increasing effect than the coconut shell activated carbon having a small specific surface area.

  From the results of Example 3, it was found that when the ratio of the activated carbon was increased to 75 wt%, the DC resistance slightly increased with the increase in capacity. From Examples 4 and 5 and Comparative Examples 4 and 5, even when the ratio of the nitroxyl compound is 30 wt% and 50 wt%, the effect of increasing the capacity can be seen without significant increase in DC resistance by mixing with activated carbon. I understood.

  By comparing Example 6 and Comparative Example 4, it was found that even when there was no lithium supply source 3, the effect of increasing the capacity was seen by mixing activated carbon. From the results of Example 7 and Comparative Example 5, it was found that when the proportion of the nitroxyl compound was increased to 70 wt%, the effect of increasing the capacity due to mixing with activated carbon was reduced.

  Since the power storage device of the present invention can simultaneously achieve high energy density and high output characteristics, low environmental load, and high safety, various types of storage power sources for driving or auxiliary use such as electric vehicles and hybrid electric vehicles, or high output are required. Can be used as a power source for portable electronic devices, a power storage device for various types of energy such as solar energy and wind power generation, or a storage power source for household appliances

It is sectional drawing which shows the structure of the electrical storage device quoted in embodiment. It is a charging / discharging curve of the electrical storage device produced in Example 1 and Comparative Example 1. FIG. It is the discharge current density dependence of the cell voltage in the electrical storage device produced in Example 1 and Comparative Example 1. FIG.

Explanation of symbols

1 Positive electrode
1A Positive electrode current collector
1B Positive lead
2 Negative electrode
2A Negative electrode current collector
2B Negative electrode lead
3 Lithium supply source
3A Lithium source collector
4 Separator
5 exterior body

Claims (5)

An electricity storage device comprising a positive electrode, a negative electrode, and a separator including an electrolyte disposed therebetween,
The positive electrode has a nitroxyl cation partial structure represented by formula (I) in an oxidized state, and a nitroxyl compound having a nitroxyl radical partial structure represented by formula (II) in a reduced state, and activated carbon particles,
The negative electrode includes a substance capable of reversibly supporting lithium ions,
An electricity storage device, wherein the electrolyte is an aprotic organic solvent containing a lithium salt.

In the oxidized state, the nitroxyl compound is a 2,2,6,6-tetramethylpiperidinoxyl cation represented by the following formula (1), a 2,2,5,5-tetramethylpyrrole represented by the formula (2) 2. The electricity storage device according to claim 1, which has at least one structure selected from the group consisting of a dinoxyl cation and a 2,2,5,5-tetramethylpyrrolinoxyl cation represented by the formula (3). .

The electrical storage device according to claim 1, wherein the activated carbon particles have a specific surface area of 1000 m ² / g or more.   4. The electricity storage device according to claim 3, wherein the activated carbon particles are phenol resin activated carbon, petroleum pitch activated carbon, petroleum coke activated carbon, or coal coke activated carbon.   Each of the positive electrode and / or the negative electrode includes a current collector having holes penetrating the front and back surfaces, and the current collector is preliminarily provided with lithium ions by electrochemical contact between the negative electrode and a lithium ion supply source. The electric storage device according to claim 1, wherein the electric storage device is doped.

Images