JP2013098123A - Binder composition for electrode, slurry for electrode, electrode, and energy storage device - Google Patents

Abstract

Provided is an electrode binder capable of producing an electricity storage device having excellent adhesion and excellent charge / discharge characteristics.
The electrode binder composition according to the present invention comprises polymer particles (A) having a number average particle diameter in the range of 50 to 400 nm and a dispersion medium (B), and the polymer particles The ratio (Rmax / Rmin) between the major axis (Rmax) and the minor axis (Rmin) of (A) is in the range of 1.1 to 1.5.
[Selection] Figure 4

Description

  The present invention relates to an electrode binder composition, an electrode slurry containing the binder composition and an electrode active material, an electrode formed by applying the slurry to a current collector, and an electricity storage device including the electrode. .

  In recent years, a power storage device having a high voltage and a high energy density has been required as a power source for driving electronic equipment. In particular, lithium ion batteries and lithium ion capacitors are expected as power storage devices having high voltage and high energy density.

  The electrode for an electricity storage device used for such an electricity storage device is usually produced by applying and drying a mixture of active material particles and polymer particles functioning as an electrode binder on the surface of the current collector. The properties required for the polymer particles used as the binder for the electrode include the bonding between the active material particles and the bonding ability between the active material particles and the current collector, the abrasion resistance in the step of winding the electrode, There is a powder fall resistance in which fine powder of the active material is not generated from the electrode composition layer (hereinafter also referred to as “active material layer”) applied by cutting or the like. When the polymer particles satisfy these required characteristics, the degree of freedom in the structural design of the electricity storage device, such as the method of folding the obtained electrode and the setting of the winding radius, is increased, and the size reduction of the electricity storage device is achieved. Can do.

  In addition, it has been empirically clarified that the quality of the active material particles is substantially proportional to the ability to bind the active material particles, the binding ability between the active material particles and the current collector, and the powder-off resistance. . Therefore, in the present specification, these may be collectively expressed below using the term “adhesion”.

  In the case of the positive electrode, the polymer used as the electrode binder is advantageously a fluorine-containing organic polymer having excellent ionic conductivity and oxidation resistance, such as polyvinylidene fluoride (PVDF (registered trademark)). is there. In the case of the negative electrode, it is advantageous to use a (meth) acrylic acid-based polymer that is inferior in oxidation resistance but excellent in adhesion. For these polymers, various techniques for further improving adhesion while maintaining ionic conductivity and oxidation resistance have been proposed.

  For example, Patent Document 1 proposes a technique for making lithium ion conductivity and oxidation resistance and adhesion of a negative electrode binder compatible by using PVDF (registered trademark) and a rubber polymer in combination. ing. In Patent Document 2, PVDF (registered trademark) is dissolved in a specific organic solvent, applied to the surface of the current collector, and then subjected to a process of removing the solvent at a low temperature to improve adhesion. Techniques to do this have been proposed. Further, Patent Document 3 proposes a technique for improving adhesion by applying an electrode binder having a structure having a side chain having a fluorine atom to a main chain made of a vinylidene fluoride copolymer. Furthermore, a technique for improving the above characteristics by controlling the binder composition (see Patent Document 4) and a technique for improving the above characteristics using a binder having an epoxy group or a hydroxyl group (see Patent Documents 5 and 6) are studied. Has been.

JP 2011-3529 A JP 2010-55847 A JP 2002-42819 A JP 2000-299109 A JP 2010-205722 A JP 2010-3703 A

  However, according to the technique disclosed in Patent Document 1 that uses both a fluorine-containing organic polymer and a rubber-based polymer, the adhesion is improved, but the ionic conductivity of the organic polymer is reduced and the oxidation resistance is greatly impaired. Therefore, an electricity storage device manufactured using this has a problem that charge / discharge characteristics are irreversibly deteriorated by repeated charge / discharge. On the other hand, according to the techniques of Patent Documents 2 and 3 using only a fluorine-containing organic polymer as an electrode binder, the level of adhesion is still insufficient. Moreover, although the binder composition like patent document 4 and 5 improves adhesiveness, the binder itself adhering to an active material becomes a resistance component of an electrode, and it is difficult to maintain favorable charging / discharging characteristics over a long period of time. there were.

  Accordingly, some aspects of the present invention provide an electrode binder composition that can produce an electricity storage device that has excellent adhesion and excellent charge / discharge characteristics by solving the above-described problems.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following aspects or application examples.

[Application Example 1]
One aspect of the binder composition for electrodes according to the present invention is:
Polymer particles (A) having a number average particle diameter in the range of 50 to 400 nm;
A dispersion medium (B);
Containing
The ratio (Rmax / Rmin) of the major axis (Rmax) to the minor axis (Rmin) of the polymer particles (A) is in the range of 1.1 to 1.5.

[Application Example 2]
In the binder composition for electrodes of Application Example 1,
The polymer particles (A) are
A repeating unit (a) derived from a fluorine-containing compound;
A repeating unit (b) derived from a polyfunctional (meth) acrylic acid ester;
Can be contained at least.

[Application Example 3]
In the binder composition for electrodes of Application Example 2,
The quantity ratio of the monomer constituting the repeating unit (a) and the monomer constituting the repeating unit (b) may be in the range of 2: 1 to 10: 1 on a mass basis.

[Application Example 4]
The binder composition for electrodes of Application Example 2 or Application Example 3 can be used for producing a positive electrode of an electricity storage device.

[Application Example 5]
In the binder composition for electrodes of Application Example 1,
The polymer particles (A) are
A repeating unit (c) derived from an unsaturated carboxylic acid;
A repeating unit (b) derived from a polyfunctional (meth) acrylic acid ester;
Can be contained at least.

[Application Example 6]
In the electrode binder composition of Application Example 5,
The quantitative ratio between the monomer constituting the repeating unit (c) and the monomer constituting the repeating unit (b) may be in the range of 1: 1 to 1: 3 on a mass basis.

[Application Example 7]
The binder composition for electrodes of Application Example 5 or Application Example 6 can be used for producing a negative electrode of an electricity storage device.

[Application Example 8]
In the electrode binder composition of any one of Application Examples 1 to 7,
When differential scanning calorimetry (DSC) was performed on the polymer particles (A) according to JIS K7121, one endothermic peak in the temperature range of -30 ° C to 30 ° C and a temperature of 80 ° C to 150 ° C One endothermic peak in the range can be observed.

[Application Example 9]
One aspect of the slurry for electrodes according to the present invention is:
It contains the binder composition for electrodes as described in any one of the application examples 1 to 8, and an electrode active material.

[Application Example 10]
One aspect of the electrode for an electricity storage device according to the present invention is:
It is characterized by comprising: a current collector; and an electrode active material layer produced by applying and drying the electrode slurry of Application Example 9 on the surface of the current collector.

[Application Example 11]
One aspect of the electricity storage device according to the present invention is:
The power storage device electrode of Application Example 10 is provided.

  According to the binder composition for an electrode according to the present invention, it is possible to produce an electrode excellent in the binding ability between active material particles and the binding ability between the active material particles and the current collector as well as the powder fall resistance, so-called adhesion. it can. Moreover, according to an electrical storage device provided with the electrode manufactured using the binder composition for electrodes which concerns on this invention, the discharge rate characteristic which is one of the electrical characteristics becomes very favorable.

It is explanatory drawing which shows typically the concept of the long diameter and short diameter of a polymer particle (A). It is explanatory drawing which shows typically the concept of the long diameter and short diameter of a polymer particle (A). It is explanatory drawing which shows typically the concept of the long diameter and short diameter of a polymer particle (A). It is explanatory drawing which shows the concept of an irregular shape particle | grain schematically. It is explanatory drawing which shows the concept of an irregular shape particle | grain schematically. It is explanatory drawing which shows the concept of an irregular shape particle | grain schematically. It is explanatory drawing which shows the concept of an irregular shape particle | grain schematically. It is explanatory drawing which shows the concept of an irregular shape particle | grain schematically. It is explanatory drawing which shows the concept of an irregular shape particle | grain schematically. It is explanatory drawing which shows typically the production | generation mechanism of irregular-shaped particle | grains. It is explanatory drawing which shows typically the production | generation mechanism of irregular-shaped particle | grains. It is explanatory drawing which shows typically the production | generation mechanism of irregular-shaped particle | grains.

  Hereinafter, preferred embodiments according to the present invention will be described in detail. It should be understood that the present invention is not limited only to the embodiments described below, and includes various modifications that are implemented within a scope that does not change the gist of the present invention. In the present specification, “(meth) acrylic acid” is a concept encompassing both “acrylic acid” and “methacrylic acid”. Further, “˜ (meth) acrylic acid ester” is a concept encompassing both “˜acrylic acid ester” and “˜methacrylic acid ester”.

1. Electrode binder composition The electrode binder composition according to the present embodiment contains polymer particles (A) having a number average particle diameter in the range of 50 to 400 nm, and a dispersion medium (B), The ratio (Rmax / Rmin) of the major axis (Rmax) and the minor axis (Rmin) of the polymer particles (A) is in the range of 1.1 to 1.5. Hereinafter, each component contained in the binder composition for electrodes which concerns on this Embodiment is demonstrated in detail.

1.1. Polymer particles (A)
1.1.1. Shape and size of polymer particles (A) The polymer particles (A) contained in the electrode binder composition according to the present embodiment have a number average particle diameter (Da) of 50 to 400 nm and a long diameter (Rmax ) And the minor axis (Rmin) (Rmax / Rmin) is 1.1 to 1.5.

  The number average particle diameter (Da) of the polymer particles (A) may be in the range of 50 to 400 nm, and is preferably in the range of 100 to 250 nm. When the number average particle diameter of the polymer particles is in the above range, the polymer particles can be sufficiently adsorbed on the surface of the active material particles, so that the polymer particles move following the movement of the active material particles. be able to. As a result, since only one of the particles can be prevented from migrating alone, deterioration of electrical characteristics can be reduced. If the number average particle diameter of the polymer particles is less than the above range, the electrical characteristics deteriorate due to migration of any of the above particles, such being undesirable. On the other hand, when the number average particle diameter of the polymer particles exceeds the above range, the ratio of the surface area to the addition amount of the polymer particles becomes small, so that good binder characteristics cannot be expressed. As a result, the adhesiveness is lowered, which is not preferable.

  The number average particle size (Da) of the polymer particles is a particle size distribution measuring device using a light scattering method as a measurement principle, and a cumulative frequency of the number of particles when particles are accumulated from small particles. The particle diameter (D50) is 50%. Examples of such a particle size distribution measuring apparatus include Coulter LS230, LS100, LS13320 (above, manufactured by Beckman Coulter. Inc), FPAR-1000 (manufactured by Otsuka Electronics Co., Ltd.), and the like. These particle size distribution measuring devices are not intended to evaluate only primary particles of polymer particles, but can also evaluate secondary particles formed by aggregation of primary particles. Therefore, the particle size distribution measured by these particle size distribution measuring devices can be used as an indicator of the dispersion state of the polymer particles contained in the electrode binder composition. The number average particle diameter (Da) of the polymer particles can also be determined by a method in which the slurry for electrodes described later is centrifuged to precipitate the active material particles, and then the supernatant is measured by the above particle size distribution measuring apparatus. Can be measured.

  The ratio (Rmax / Rmin) between the major axis (Rmax) and the minor axis (Rmin) of the polymer particles (A) may be in the range of 1.1 to 1.5, and is in the range of 1.2 to 1.4. It is preferable that it exists in. When the ratio (Rmax / Rmin) is within the above range, the surface area of the polymer particles (A) increases and the surface of the polymer particles (A) is not a true curved surface. In addition, the adhesion between the current collector and the active material layer is improved. As a result, the electrical characteristics of the electricity storage device are improved. When the ratio (Rmax / Rmin) is less than the above range, the polymer particles (A) are close to true spheres, so that they are less likely to come into contact with active material particles close to true spheres, and the binding properties between the active material particles are low. In addition, the adhesion between the current collector and the active material layer tends to decrease. As a result, the electrode tends to crack, and the electrical characteristics of the electricity storage device tend to be impaired. On the other hand, when the ratio (Rmax / Rmin) exceeds the above range, the surface area of the polymer particles (A) increases, but it becomes difficult to contact the active material particles close to the true sphere, and the binding property between the active material particles is increased. In addition, the adhesion between the current collector and the active material layer tends to decrease. As a result, the electrode tends to crack, and the electrical characteristics of the electricity storage device tend to be impaired.

  The major axis (Rmax) of the polymer particle means the distance of the longest straight line among the straight lines connecting the end portions of the image of one independent polymer particle taken by a transmission electron microscope. The short diameter (Rmin) means the distance of the shortest straight line among the straight lines connecting the end portions of the image.

  For example, when the image of one independent polymer particle 10a photographed by a transmission electron microscope as shown in FIG. 1 is elliptical, the major axis a of the elliptical shape is defined as the major axis (Rmax) of the polymer particle. The minor axis b is judged as the minor axis (Rmin) of the polymer particles. As shown in FIG. 2, when an image of 10 b of one independent polymer particle taken by a transmission electron microscope is an aggregate of two primary particles, a straight line connecting the end portions of the image Of these, the longest distance c is determined as the long diameter (Rmax) of the polymer particles, and the shortest diameter d of the straight lines connecting the end portions of the image is determined as the short diameter (Rmin) of the polymer particles. As shown in FIG. 3, when the image of 10 c of one independent polymer particle photographed by a transmission electron microscope is an aggregate of three or more primary particles, the ends of the image are connected to each other. The longest distance e of the straight lines is determined as the long diameter (Rmax) of the polymer particles, and the shortest diameter f of the straight lines connecting the end portions of the image is determined as the short diameter (Rmin) of the polymer particles. .

  For example, by measuring the major axis (Rmax) and minor axis (Rmin) of 10 polymer particles by the above-described determination method, and calculating the average value of the major axis (Rmax) and minor axis (Rmin), the major axis and The ratio to the minor axis (Rmax / Rmin) can be calculated and obtained.

  The polymer particles (A) may be “deformed particles” having a structure in which the first polymer particles and the second polymer particles are in close contact with each other. In this case, the polymer particle (A) can have a structure in which the other polymer particle is disposed on at least a part of the surface of one of the polymer particles. Here, “an irregular shape” in the present specification means that two particles are arranged asymmetrically with respect to the center point of the whole particle.

  4 to 9 are explanatory views schematically showing the concept of irregularly shaped particles. Examples of the “irregular particles” include structures as shown in FIGS.

  In the irregularly shaped particle 20a shown in FIG. 4, the second polymer particle 24a is in close contact with a part of the surface of the first polymer particle 22a, and the second polymer particle 24a is the first polymer particle 22a. It has a structure protruding from the surface.

  The deformed particle 20b shown in FIG. 5 includes the first polymer particle 22b completely including the second polymer particle 24b, and the second polymer particle 22b has a second weight at one point on the surface of the first polymer particle 22b. It is in contact with the coalesced particles 24b and has a substantially spherical structure as a whole.

  The deformed particle 20c shown in FIG. 6 has a substantially spherical structure as a whole, with the first polymer particle 22c and the second polymer particle 24c being in close contact with each other. In the deformed particle 20c shown in FIG. 6, the first polymer particle 22c and the second polymer particle 24c have the same surface area, but this is not particularly limited.

  The deformed particle 20d shown in FIG. 7 includes the second polymer particle 24d inside the first polymer particle 22d, and the curved surface of the second polymer particle 24d appears on the surface of the deformed particle 20d. As a whole, it has a substantially spherical structure.

  The deformed particle 20e shown in FIG. 8 has an oval spherical structure like a rugby ball as a whole of the deformed particle 20c shown in FIG. In addition, in the irregular shaped particle 20e shown in FIG. 8, the first polymer particle 22e and the second polymer particle 24e have the same surface area, but this point is not particularly limited.

  The deformed particle 20f shown in FIG. 9 has a substantially spherical first polymer particle 22f and a substantially spherical second polymer particle 24f in close contact with each other, and has a twin-spherical structure as a whole. Yes.

  The irregularly shaped particles that can be used in the present embodiment are preferably composed of the first polymer particles and the second polymer particles as described above. In such a case, the composition of the first polymer particles and the composition of the second polymer particles may be the same or different, but at least of the monomer units contained in the first polymer particles. One type is preferably different from the monomer unit contained in the second polymer particle. That is, in this case, at least one kind of monomer units constituting the irregularly shaped particles is contained only in one of the first polymer particles and the second polymer particles. It will be. Thereby, as shown in FIGS. 4 to 9, the first polymer particles and the second polymer particles can be asymmetrically separated.

  When the polymer particles (A) are irregularly shaped particles, since the irregularly shaped particles substantially constitute one particle, the major axis and minor axis of the irregularly shaped particles are measured as follows. For example, when the polymer particle (A) is a substantially spherical particle 20a having spherical protrusions as shown in FIG. 4, the major axis (Rmax) is the second polymer particle from the end of the first polymer particle 22a. It is represented by the distance to the end of 24a. The short diameter (Rmin) is represented by the diameter of the larger particle (first polymer particle 22a in FIG. 4).

  In the electrode binder composition according to the present embodiment, the polymer particles (A) as described above are dispersed in the dispersion medium (B). In addition, the binder composition for electrodes which concerns on this Embodiment can be used for both a positive electrode and a negative electrode. When used for producing a positive electrode, the polymer particle (A) comprises a repeating unit (a) derived from a fluorine-containing compound and a repeating unit (b) derived from a polyfunctional (meth) acrylate. It is preferable to contain at least. On the other hand, when used for producing a negative electrode, the polymer particles (A) are a repeating unit (c) derived from an unsaturated carboxylic acid and a repeating unit (b) derived from a polyfunctional (meth) acrylic ester. It is preferable to contain at least. Hereinafter, the repeating unit which comprises a polymer particle (A) is demonstrated.

1.1.2. Repeating units constituting the polymer particles (A) 1.1.2.1. Repeating unit derived from fluorine-containing compound (a)
The polymer particles (A) preferably contain a repeating unit (a) derived from a fluorine-containing compound. The repeating unit (a) derived from the fluorine-containing compound is preferably a repeating unit (a) derived from the fluorine-containing compound having an ethylenically unsaturated bond. Among the fluorine-containing compounds having an ethylenically unsaturated bond, at least one selected from the group consisting of vinylidene fluoride, ethylene tetrafluoride and propylene hexafluoride is particularly preferable. When the polymer particles (A) have the repeating unit (a), ionic conductivity and oxidation resistance are improved. For this reason, it is particularly suitable when the electrode binder composition according to the present embodiment is used for producing a positive electrode. This is because, when polymer particles having low oxidation resistance are used in the positive electrode of the electricity storage device, good charge / discharge characteristics cannot be obtained because they are oxidized and decomposed by repeated charge / discharge.

  The content ratio of the repeating unit (a) in the polymer particles (A) is preferably 1 part by mass or more and more preferably 10 parts by mass or more with respect to 100 parts by mass of the polymer particles (A). .

1.1.2.2. Repeating unit (b) derived from polyfunctional (meth) acrylic acid ester
The polymer particles (A) preferably contain a repeating unit (b) derived from a polyfunctional (meth) acrylic acid ester. When the polymer particles (A) contain the repeating unit (b), it becomes easy to produce irregular shaped particles as described above. That is, according to the example of the irregularly shaped particles shown in FIGS. 4 to 9 described above, the repeating unit (b) existing on the surface and / or the inside of the first polymer particle serving as the seed particle serves as a starting point or an opportunity. As a result, second polymer particles are formed. The generation mechanism will be described in detail later.
In the present invention, “polyfunctional” means at least one selected from the group consisting of a polymerizable double bond, an epoxy group, and a hydroxyl group, in addition to the polymerizable double bond of (meth) acrylic acid ester. It has the functional group of.

  Specific examples of polyfunctional (meth) acrylic acid esters include glycidyl (meth) acrylate, hydroxymethyl (meth) acrylate, hydroxyethyl (meth) acrylate, allyl (meth) acrylate, and di (meth) acrylic acid. Ethylene glycol, propylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, ethylene di (meth) acrylate, etc. And can be one or more selected from these. Of these, at least one selected from glycidyl (meth) acrylate and hydroxyethyl (meth) acrylate is preferable, and glycidyl (meth) acrylate is particularly preferable.

  The content ratio of the repeating unit (b) in the polymer particles (A) is preferably 1 to 10 parts by mass, and 2 to 8 parts by mass with respect to 100 parts by mass of the polymer particles (A). More preferred. It is preferable for the content ratio to be in the above-mentioned range since it becomes easy to produce irregular shaped particles as described above. When the content ratio is less than the above range, the contact area between the particles becomes small, so the first polymer particles and the second polymer particles may not adhere to each other, and irregular shaped particles may not be produced. Absent. On the other hand, if the content ratio exceeds the above range, the entire surface of the seed particle is covered with the repeating unit (b), so that it may become a so-called core-shell particle and it may not be possible to produce a deformed particle.

  In addition, when the binder composition for electrodes which concerns on this Embodiment is used in order to produce a positive electrode, the monomer which comprises the said repeating unit (a), and the monomer which comprises the said repeating unit (b) Is preferably in the range of 2: 1 to 10: 1, and more preferably in the range of 3: 1 to 9: 1. A quantitative ratio in the above range is preferable because it becomes easier to produce irregularly shaped particles as described above.

  On the other hand, when the electrode binder composition according to the present embodiment is used for producing a negative electrode, the monomer constituting the repeating unit (c) and the monomer constituting the repeating unit (b) are described below. Is preferably in the range of 1: 1 to 1: 3, more preferably in the range of 1: 2 to 1: 3. A quantitative ratio in the above range is preferable because it becomes easier to produce irregularly shaped particles as described above.

1.1.2.3. Repeating unit derived from unsaturated carboxylic acid (c)
The polymer particles (A) preferably contain a repeating unit (c) derived from an unsaturated carboxylic acid. When the polymer particles (A) have the structural unit (c) derived from the unsaturated carboxylic acid, the stability of the electrode slurry using the electrode binder composition of the present invention is improved.

  Specific examples of the unsaturated carboxylic acid include mono- or dicarboxylic acids (anhydrides) such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, and the like. It can be more than a seed. In particular, at least one selected from acrylic acid, methacrylic acid and itaconic acid is preferable.

  The content ratio of the repeating unit (c) in the polymer particles (A) is preferably 15 parts by mass or less, and 0.3 to 10 parts by mass with respect to 100 parts by mass of the polymer particles (A). Is more preferable. When the content ratio of the repeating unit (c) is in the above range, the dispersion stability of the polymer particles (A) is excellent during the preparation of the electrode slurry, and aggregates are hardly generated. Further, an increase in slurry viscosity over time can be suppressed.

1.1.2.4. Repeating unit derived from monofunctional (meth) acrylic acid ester (d)
The polymer particle (A) preferably further contains a repeating unit (d) derived from a monofunctional (meth) acrylic ester. When the polymer particle (A) has a structural unit (d) derived from a monofunctional (meth) acrylic acid ester compound, the resulting polymer particle (A) has an appropriate affinity with the electrolytic solution. In addition, it is possible to suppress an increase in internal resistance due to the binder becoming an electrical resistance component in the electricity storage device, and to prevent a decrease in binding property due to excessive absorption of the electrolytic solution.
In the present invention, “monofunctional” is selected from the group consisting of a polymerizable double bond, an epoxy group, a hydroxyl group, and a carboxylic acid in addition to the polymerizable double bond of (meth) acrylic acid ester. It indicates that it does not have at least one functional group.

  Specific examples of such monofunctional (meth) acrylic acid esters include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, N-butyl (meth) acrylate, i-butyl (meth) acrylate, n-amyl (meth) acrylate, i-amyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, (Meth) acrylic acid 2-ethylhexyl, (meth) acrylic acid n-octyl, (meth) acrylic acid nonyl, (meth) acrylic acid decyl, etc. can be mentioned, and one or more selected from these be able to. Among these, at least one selected from methyl (meth) acrylate, ethyl (meth) acrylate and 2-ethylhexyl acrylate is preferable, and methyl (meth) acrylate is particularly preferable.

  The content ratio of the repeating unit (d) in the polymer particles (A) is preferably 40 parts by mass or more and more preferably 45 parts by mass or more with respect to 100 parts by mass of the polymer particles (A). . When the content ratio of the repeating unit (d) is within the above range, the resulting polymer particles (A) have an appropriate affinity with the electrolytic solution, and the internal content of the binder as an electrical resistance component in the electricity storage device. While suppressing an increase in resistance, it is possible to prevent a decrease in binding property due to excessive absorption of the electrolytic solution.

1.1.2.5. Repeating units derived from α, β-unsaturated nitrile compounds (e)
The polymer particle (A) preferably further contains a repeating unit (e) derived from an α, β-unsaturated nitrile compound. When polymer particle (A) has a repeating unit (e), the swelling property with respect to the electrolyte solution of polymer particle (A) can be improved more. That is, the presence of a nitrile group makes it easier for the solvent to enter the network structure composed of polymer chains and the network interval is widened, so that the solvated lithium ions can easily move through the network structure. Thereby, it is thought that the diffusibility of lithium ion improves, As a result, electrode resistance falls and it can implement | achieve more favorable charging / discharging characteristics.

  Specific examples of the α, β-unsaturated nitrile compound include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile, vinylidene cyanide and the like. Can be. Among these, at least one selected from acrylonitrile and methacrylonitrile is preferable, and acrylonitrile is particularly preferable.

  The content ratio of the repeating unit (e) in the polymer particles (A) is preferably 35 parts by mass or less and more preferably 10 to 25 parts by mass with respect to 100 parts by mass of the polymer particles (A). preferable. When the content ratio of the repeating unit (e) is in the above range, the compatibility with the electrolyte solution to be used is excellent, and the swelling rate does not become too large, which can contribute to the improvement of battery characteristics.

1.1.2.6. Repeating unit (f) derived from conjugated diene compound
The polymer particle (A) preferably further contains a repeating unit (f) derived from a conjugated diene compound. When polymer particle (A) has a repeating unit (f), it becomes easy to manufacture polymer particle (A) excellent in viscoelastic properties and strength. That is, when the polymer particle (A) having the repeating unit (f) is used, the polymer particle (A) can have a strong binding force. That is, since rubber elasticity derived from the conjugated diene compound is imparted to the polymer particles (A), it becomes possible to follow changes such as volume shrinkage and expansion of the electrode. Thereby, it is thought that it has the durability which improves a binding property and maintains a charging / discharging characteristic for a long term.

  Specific examples of the conjugated diene compound include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene and the like. It can be one or more selected from these. Of the above, 1,3-butadiene is particularly preferable as the conjugated diene compound.

  The content ratio of the repeating unit (f) in the polymer particles (A) is preferably 35 parts by mass or less and more preferably 25 parts by mass or less with respect to 100 parts by mass of the polymer particles (A). . When the content ratio of the repeating unit (f) is in the above range, the binding property can be further improved.

1.1.2.7. Repeating units derived from aromatic vinyl compounds (g)
The polymer particles (A) preferably further contain a repeating unit (g) derived from an aromatic vinyl compound. When the polymer particles (A) have the repeating unit (g), when the electrode slurry contains a conductivity-imparting agent, the affinity for this can be made better.

  Specific examples of the aromatic vinyl compound include styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, chlorostyrene, divinylbenzene, and the like, and one or more selected from these can be used. be able to. Among the above, the aromatic vinyl compound is particularly preferably styrene.

  The content ratio of the repeating unit (g) in the polymer particles (A) is preferably 50 parts by mass or less and more preferably 45 parts by mass or less with respect to 100 parts by mass of the polymer particles (A). . When the content ratio of the repeating unit (g) is within the above range, the polymer particles have an appropriate binding property to graphite used as an active material. In addition, the obtained electrode layer has excellent flexibility and binding property to the current collector.

1.1.2.8. Repeating units derived from other compounds The polymer particles (A) may further contain repeating units derived from compounds other than those described above, if necessary. Specific examples of other compounds include alkyl amides of ethylenically unsaturated carboxylic acids such as (meth) acrylamide and N-methylol acrylamide; vinyl carboxylic acid esters such as vinyl acetate and vinyl propionate; ethylenically unsaturated dicarboxylic acids Monoalkyl esters; monoamides; aminoalkyl amides of ethylenically unsaturated carboxylic acids such as aminoethyl acrylamide, dimethylaminomethyl methacrylamide, methylaminopropyl methacrylamide, and the like. Can be one or more.

1.1.3. Characteristics of polymer particles (A) 1.1.3.1. Thermal properties of polymer particles (A) The polymer particles (A) have one endothermic peak in the temperature range of -30 ° C to 30 ° C when measured by differential scanning calorimetry (DSC) in accordance with JIS K7121. One endothermic peak in the temperature range of 80 ° C. to 150 ° C. is preferably observed. When two endothermic peaks are observed in this way, it is understood that the polymer particles (A) are irregularly shaped particles formed from two types of polymer particles having different components. When one temperature of the endothermic peak of the polymer particle (A) is in the range of −30 to + 30 ° C., the particle can impart better flexibility and tackiness to the active material layer. Therefore, the adhesion can be further improved.

1.1.3.2. Tetrahydrofuran (THF) Insoluble Content The THF insoluble content of the polymer particles (A) is preferably 80% or more, and more preferably 90% or more. The THF-insoluble content is estimated to be approximately proportional to the amount of insoluble content in the electrolytic solution used in the electricity storage device. For this reason, if the THF-insoluble content is within the above range, it is preferable that an electricity storage device is produced and elution of the polymer particles (A) into the electrolytic solution can be suppressed even when charging / discharging is repeated for a long period of time. I can guess.

1.1.4. Production method of polymer particle (A) The polymer particle (A) contained in the electrode binder composition according to the present embodiment is not particularly limited as long as it has the above-described configuration. However, it can be easily synthesized by, for example, a known emulsion polymerization process or an appropriate combination thereof. For example, it can be produced by the method described in JP-A-2007-197588.

  The polymer particles (A) contained in the electrode binder composition according to the present embodiment can be produced, for example, according to the following method. First, the first polymer particles can be obtained by a usual emulsion polymerization method using an aqueous medium. The “aqueous medium” means a medium containing water as a main component. Specifically, the water content in the aqueous medium is preferably 40% by mass or more, and more preferably 50% by mass or more. Other media that can be used in combination with water include compounds such as esters, ketones, phenols, and alcohols.

  The conditions for emulsion polymerization may be in accordance with known methods. For example, when the total amount of monomers used is 100 parts, usually 100 to 500 parts of water is used, and the polymerization temperature is −10 to 100 ° C. (preferably −5 to 100 ° C., more preferably 0 to 90 ° C. ), Polymerization time can be carried out under conditions of 0.1 to 30 hours (preferably 2 to 25 hours). As a method of emulsion polymerization, a batch method in which monomers are charged all together, a method in which monomers are divided or continuously supplied, a method in which a monomer pre-emulsion is divided or continuously added, or these A method that combines methods in stages can be adopted. Moreover, the molecular weight regulator used for normal emulsion polymerization, a chelating agent, an inorganic electrolyte, etc. can be used 1 type, or 2 or more types as needed.

  When an initiator is used in the emulsion polymerization, the initiator includes persulfates such as potassium persulfate and ammonium persulfate; benzoyl peroxide, lauroyl peroxide, tert-butylperoxy-2-ethylhexanoate, etc. Organic peroxides; azo compounds such as azobisisobutyronitrile, dimethyl-2,2′-azobisisobutyrate, 2-carbamoylazaisobutyronitrile; containing radical emulsifying compounds having a peroxide group A redox system combining a reducing agent such as a radical emulsifier, sodium hydrogen sulfite, and ferrous sulfate; Moreover, when using an emulsifier, 1 or more types selected from the group which consists of a well-known anionic emulsifier, a nonionic emulsifier, and an amphoteric emulsifier can be used as this emulsifier. In addition, you may use the reactive emulsifier etc. which have an unsaturated double bond in a molecule | numerator.

  There is no restriction | limiting in particular in the molecular weight modifier used for emulsion polymerization. Specific examples of molecular weight regulators include n-hexyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-hexadecyl mercaptan, n-tetradecyl mercaptan, t-tetradecyl mercaptan, thioglycolic acid Mercaptans such as dimethyl xanthogen disulfide, diethyl xanthogen disulfide, diisopropyl xanthogen disulfide, etc .; Xanthogen disulfides such as tetramethyl thiuram disulfide, tetraethyl thiuram disulfide, tetrabutyl thiuram disulfide; chloroform, carbon tetrachloride, tetrabromide Halogenated hydrocarbons such as carbon and ethylene bromide; hydrocarbons such as pentaphenylethane and α-methylstyrene dimer; Kurorein, methacrolein, allyl alcohol, 2-ethylhexyl thioglycolate, terpinolene, alpha-Terunepin, .gamma. Terunepin can include dipentene, 1,1-diphenylethylene and the like. These molecular weight regulators can be used singly or in combination of two or more. Of these, mercaptans, xanthogen disulfides, thiuram disulfides, 1,1-diphenylethylene, α-methylstyrene dimer and the like are more preferably used.

  The polymerization conversion rate of the monomer at the end of the emulsion polymerization is preferably 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 95% by mass or more. The first polymer particles and the second polymer particles formed when the monomer for the second polymer particles is added in a state where the polymerization addition rate of the first polymer particles is less than 80% by mass. It becomes difficult to clearly separate. The obtained first polymer particles are usually substantially spherical particles.

  In the presence of the obtained first polymer particles, the monomer for the second polymer particles is polymerized. More specifically, the second polymer particles are formed by seed-polymerizing the monomer for the second polymer particles in a state where the obtained first polymer particles are used as seed particles. be able to. For example, the second polymer particle monomer or a pre-emulsion thereof may be added all at once, in a divided manner, or continuously in an aqueous medium in which the first polymer particles are dispersed. The amount of the first polymer particles used at this time is preferably 1 to 100 parts by mass, and preferably 2 to 80 parts by mass with respect to 100 parts by mass of the monomer for the second polymer particles. It is more preferable. When an initiator or an emulsifier is used in the polymerization, the same one as used in the production of the first polymer particles can be used. Also, the conditions such as the polymerization time may be the same as in the production of the first polymer particles.

  10 to 12 are explanatory views schematically showing a generation mechanism of irregularly shaped particles. As shown in FIG. 10, when the second polymer particle monomer 23 is introduced into the aqueous medium in which the first polymer particles 22 are dispersed, the second polymer particle monomer is introduced. Most of 23 is normally occluded once by the first polymer particles, and the polymerization is started in or on the surface of the first polymer particles 22. The second polymer particle monomer 23 decreases in compatibility with the first polymer particle 22 as the polymerization proceeds, and phase-separates with the first polymer particle 22. Therefore, at the initial stage of the polymerization, the polymerization can proceed at a plurality of locations of the first polymer particles 22 as shown in FIG. 11, but the monomer units constituting each polymer have been described so far. If the relationship is satisfied, the second polymer particles 24 tend to be polymerized at various locations of the first polymer particles 22 to form a single second polymer particle 24. Then, when the second polymer particle 24 grows to a certain size, the subsequent polymerization proceeds mainly by the second polymer particle 24 as shown in FIG. In this way, deformed particles in which the first polymer particles and the second polymer particles are asymmetrically separated are formed.

  In the irregularly shaped particles formed as described above, the mass ratio (first / second) between the first polymer particles and the second polymer particles is 2/98 to 98/2. It is preferably 5/95 to 95/5. The ratio of the exposed surface formed by the first polymer particles to the exposed surface formed by the second polymer particles in the total surface area of the irregularly shaped particles (area ratio = first / second) is 5/95 to 95/5 are preferable, and 10/90 to 90/10 are more preferable. When the proportion of either one of the first polymer particles and the second polymer particles is less than the above range, the effect due to the irregular particles being “abnormal” may not be sufficiently obtained. . In addition, the ratio of the exposed surface of each primary particle which occupies for the total surface area of a deformed particle can be measured from an electron micrograph, for example.

  The shape of the irregularly shaped particles is the mass ratio between the first polymer particles and the second polymer particles, the separability between the first polymer particles and the second polymer particles, and the second polymer particles. Various changes occur depending on the polymerization conditions and the like when forming. For example, when the mass ratio between the first polymer particles and the second polymer particles and the polymerization conditions are constant, as the separability between the first polymer particles and the second polymer particles increases, The shape of irregularly shaped particles tends to change in the order of FIG. 5, FIG. 7, and FIG.

1.2. Dispersion medium (B)
The binder composition for electrodes according to the present embodiment contains a dispersion medium (B). The dispersion medium (B) is preferably an aqueous medium containing water. This aqueous medium can contain a small amount of non-aqueous medium in addition to water. Examples of such non-aqueous media include amide compounds, hydrocarbons, alcohols, ketones, esters, amine compounds, lactones, sulfoxides, sulfone compounds, and the like, and one or more selected from these are used. can do. The content ratio of such a non-aqueous medium is preferably 10 parts by mass or less, more preferably 5 parts by mass or less with respect to 100 parts by mass of the aqueous medium, and only water without containing the non-aqueous medium. It is most preferable that it consists of.

  The electrode binder composition according to the present embodiment uses an aqueous medium as a medium, and preferably contains no non-aqueous medium other than water, so that it has a low adverse effect on the environment and is safe for handling workers. Also gets higher.

1.3. Other Additives The electrode binder composition according to the present embodiment can further contain other additives as necessary in addition to the polymer particles (A) and the liquid medium (B) described above. . For example, a thickener can be contained from the viewpoint of further improving the applicability and the charge / discharge characteristics of the electricity storage device.

  Examples of such thickeners include cellulose compounds such as carboxymethylcellulose, methylcellulose, and hydroxypropylcellulose; ammonium salts or alkali metal salts of the above cellulose compounds; poly (meth) acrylic acid, modified poly (meth) acrylic acid, and the like. Polycarboxylic acid; alkali metal salt of the above polycarboxylic acid; polyvinyl alcohol (co) polymer such as polyvinyl alcohol, modified polyvinyl alcohol, ethylene-vinyl alcohol copolymer; (meth) acrylic acid, maleic acid, fumaric acid, etc. And a water-soluble polymer such as a saponified product of a copolymer of an unsaturated carboxylic acid and a vinyl ester. Among these, particularly preferred thickeners are alkali metal salts of carboxymethyl cellulose, alkali metal salts of poly (meth) acrylic acid, and the like.

  Examples of commercially available products of these thickeners include CMC 1120, CMC 1150, CMC 2200, CMC 2280, CMC 2450 (manufactured by Daicel Chemical Industries, Ltd.) and the like as alkali metal salts of carboxymethyl cellulose.

  When the binder composition for electrodes which concerns on this Embodiment contains a thickener, as a usage-ratio of a thickener, Preferably it is 15 mass% or less with respect to the total amount of solids in the binder composition for electrodes. Yes, more preferably 0.1 to 10% by mass.

2. Electrode slurry Using the electrode binder composition described above, the electrode slurry according to the present embodiment can be produced. The electrode slurry is a dispersion used to form an electrode active material layer on the current collector surface after being applied to the current collector surface and then dried. The electrode slurry according to the present embodiment contains the above-described electrode binder composition, an electrode active material, and water. Hereinafter, each component contained in the electrode slurry according to the present embodiment will be described in detail. However, the components contained in the electrode binder composition are omitted because they are as described above.

2.1. Electrode active material There is no restriction | limiting in particular as a material which comprises the electrode active material contained in the slurry for electrodes, A suitable material can be selected suitably according to the kind of the electrical storage device made into the objective.

For example, when producing a positive electrode of a lithium ion secondary battery, a lithium atom-containing oxide is preferable, and a lithium atom-containing oxide having an olivine structure is more preferable. The lithium atom-containing oxide having the olivine structure is a compound represented by the following general formula (1) and having an olivine type crystal structure.
Li _1-x M _x (XO ₄ ) (1)
(Wherein M is at least a metal ion selected from the group consisting of Mg, Ti, V, Nb, Ta, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Ge, and Sn) X is at least one selected from the group consisting of Si, S, P and V; x is a number and satisfies the relationship 0 <x <1; and Li ions and M ions The total valence of is +3.)

The lithium atom-containing oxide having the olivine structure has different electrode potentials depending on the type of the metal element M. Therefore, the battery voltage can be arbitrarily set by selecting the type of the metal element M. Typical examples of the lithium atom-containing oxide having an olivine structure include LiFePO ₄ , LiCoPO ₄ , Li _0.90 Ti _0.05 Nb _0.05 Fe _0.30 Co _0.30 Mn _0.30 PO _{4, and the} like. Can be mentioned. Among these, LiFePO ₄ is particularly preferable because it is easy to obtain an iron compound as a raw material and is inexpensive. Moreover, since the compound which substituted Fe ion in said compound by Co ion, Ni ion, or Mn ion also has the same crystal structure as said each compound, it has the same effect as an electrode active material.

  On the other hand, when producing a negative electrode of a lithium ion secondary battery, carbon can be used. Specific examples of carbon include carbon materials obtained by firing organic polymer compounds such as phenol resin, polyacrylonitrile, and cellulose; carbon materials obtained by firing coke and pitch; artificial graphite; natural graphite and the like Can be mentioned.

  When producing an electric double layer capacitor electrode, activated carbon, activated carbon fiber, silica, alumina or the like can be used. When producing lithium ion capacitor electrodes, carbon materials such as amorphous carbon, natural graphite, artificial graphite, non-graphitizable carbon, hard carbon, soft carbon, coke, polyacene organic semiconductor (PAS), etc. are used. be able to.

  The number average particle diameter (Db) of the electrode active material is preferably in the range of 0.4 to 10 μm, and more preferably in the range of 0.5 to 7 μm. When the number average particle diameter of the electrode active material is within the above range, the diffusion distance of lithium in the electrode active material is shortened, so that the resistance associated with lithium insertion / desorption during charge / discharge can be reduced, As a result, the charge / discharge characteristics are further improved. Furthermore, when the electrode slurry contains a conductivity-imparting agent described later, the contact area between the electrode active material and the conductivity-imparting agent is sufficiently ensured by the number average particle diameter of the electrode active material being within the above range. As a result, the electronic conductivity of the electrode is improved, and the electrode resistance is further reduced.

  Here, the number average particle diameter (Db) of the electrode active material is the number of particles when the particle size distribution is measured using a particle size distribution measuring apparatus based on the laser diffraction method and the particles are accumulated from small particles. This is the value of the particle diameter (D50) at which the cumulative frequency is 50%. Examples of such a laser diffraction particle size distribution measuring apparatus include HORIBA LA-300 series, HORIBA LA-920 series (above, manufactured by Horiba, Ltd.) and the like. This particle size distribution measuring apparatus is not intended to evaluate only the primary particles of the electrode active material, but also evaluates the secondary particles formed by aggregation of the primary particles. Therefore, the average particle diameter (Db) obtained by this particle size distribution measuring apparatus can be used as an indicator of the dispersion state of the electrode active material contained in the electrode slurry. The average particle diameter (Db) of the electrode active material is measured by centrifuging the electrode slurry to settle the electrode active material, then removing the supernatant and measuring the precipitated electrode active material by the above method. Can also be measured.

2.2. Other Components The electrode slurry can contain components other than the components described above as necessary. Examples of such components include a conductivity-imparting agent, a non-aqueous medium, and a thickener.

2.2.1. Conductivity-imparting agent Specific examples of the above-mentioned conductivity-imparting agent include carbon in a lithium ion secondary battery; in a nickel-hydrogen secondary battery, cobalt oxide at the positive electrode: nickel powder, cobalt oxide, titanium oxide, carbon at the negative electrode Etc. are used respectively. In both the batteries, examples of carbon include graphite, activated carbon, acetylene black, furnace black, graphite, carbon fiber, and fullerene. Among these, acetylene black or furnace black can be preferably used. The use ratio of the conductivity-imparting agent is preferably 20 parts by mass or less, more preferably 1 to 15 parts by mass, and particularly preferably 2 to 10 parts by mass with respect to 100 parts by mass of the electrode active material.

2.2.2. Non-aqueous medium The electrode slurry may contain a non-aqueous medium having a standard boiling point of 80 to 350 ° C. from the viewpoint of improving the applicability. Specific examples of such a non-aqueous medium include amide compounds such as N-methylpyrrolidone, dimethylformamide and N, N-dimethylacetamide; hydrocarbons such as toluene, xylene, n-dodecane and tetralin; 2-ethyl- Alcohols such as 1-hexanol, 1-nonanol and lauryl alcohol; ketones such as methyl ethyl ketone, cyclohexanone, phorone, acetophenone and isophorone; esters such as benzyl acetate, isopentyl butyrate, methyl lactate, ethyl lactate and butyl lactate; o-toluidine, m Examples include amine compounds such as toluidine and p-toluidine; lactones such as γ-butyrolactone and δ-butyrolactone; sulfoxide and sulfone compounds such as dimethyl sulfoxide and sulfolane, and the like. More than seeds can be used. Among these, it is preferable to use N-methylpyrrolidone from the viewpoints of stability of polymer particles, workability when applying the slurry for electrodes, and the like.

2.2.3. Thickener The said electrode slurry can contain a thickener from a viewpoint of improving the coating property. Specific examples of the thickener include various compounds described in the above-mentioned “1.3. Other additives”.

  When the electrode slurry contains a thickener, the use ratio of the thickener is preferably 20% by mass or less, more preferably 0.1 to 15% by mass with respect to the total solid content of the electrode slurry. %, Particularly preferably 0.5 to 10% by mass.

2.3. Method for Producing Electrode Slurry The electrode slurry according to the present embodiment is produced by mixing the above-mentioned electrode binder composition, electrode active material, water, and additives used as necessary. can do. These can be mixed by stirring by a known method. For example, a stirrer, a defoamer, a bead mill, a high-pressure homogenizer, or the like can be used.

The preparation of the electrode slurry (mixing operation of each component) is preferably performed at least part of the process under reduced pressure. Thereby, it can prevent that a bubble arises in the electrode layer obtained. The degree of pressure reduction is preferably about 5.0 × 10 ^{4 to} 5.0 × 10 ⁵ Pa as an absolute pressure.

  As mixing and stirring for producing the electrode slurry, it is necessary to select a mixer capable of stirring to such an extent that no aggregates of the electrode active material remain in the slurry and a sufficient dispersion condition as necessary. The degree of dispersion can be measured by a particle gauge, but it is preferable to mix and disperse so that aggregates larger than at least 100 μm are eliminated. Examples of the mixer that meets such conditions include a ball mill, a sand mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, a planetary mixer, a Hobart mixer, and the like.

2.4. Characteristics of electrode slurry The ratio (Da / Db) of the number average particle diameter (Da) of the polymer particles (A) contained in the electrode binder composition and the number average particle diameter (Db) of the electrode active material is as follows. It is preferably in the range of 0.01 to 1.0, more preferably in the range of 0.05 to 0.5. The technical meaning of this is as follows.

  It has been confirmed that at least one of the polymer particles and the electrode active material migrates in the step of drying the formed coating film after applying the electrode slurry to the surface of the current collector. That is, the particles move along the thickness direction of the coating film by receiving the action of surface tension. More specifically, at least one of the polymer particles and the electrode active material moves to the side of the coating film surface opposite to the surface in contact with the current collector, that is, the gas-solid interface side where water evaporates. To do. When such migration occurs, the distribution of the polymer particles and the electrode active material becomes uneven in the thickness direction of the coating film, causing problems such as deterioration of electrode characteristics and loss of adhesion. For example, when polymer particles functioning as a binder bleed (transfer) to the gas-solid interface side of the electrode active material layer, and the amount of polymer particles at the interface between the current collector and the electrode active material layer becomes relatively small If the penetration of the electrolytic solution into the electrode active material layer is inhibited, sufficient electrical characteristics cannot be obtained, and the binding property between the current collector and the electrode active material layer is insufficient and the electrode active material layer is peeled off. Furthermore, the smoothness of the surface of the electrode active material layer is impaired when the polymer particles bleed.

  However, when the ratio of the number average particle diameter of both particles (Da / Db) is in the above range, the occurrence of the problems as described above can be suppressed, and both good electrical characteristics and binding properties are compatible. The electrode can be easily manufactured. When the ratio (Da / Db) is less than the above range, the difference between the average particle diameters of the polymer particles and the electrode active material is small, so the area where the polymer particles and the electrode active material are in contact with each other is small, and the powder-off resistance. May become insufficient. On the other hand, when the ratio (Da / Db) exceeds the above range, the difference in the average particle diameter between the polymer particles and the electrode active material becomes too large, resulting in insufficient adhesion of the polymer particles, and the current collector. The binding between the electrode active material layer and the electrode active material layer may be insufficient.

  The electrode slurry according to the present embodiment preferably has a solid content concentration (a ratio of the total mass of components other than the solvent in the slurry to the total mass of the slurry) of 20 to 80% by mass, 30 More preferably, it is -75 mass%.

  In the electrode slurry according to the present embodiment, the spinnability is preferably 30 to 80%, more preferably 33 to 79%, and particularly preferably 35 to 78%. When the spinnability is less than the above range, the leveling property is insufficient when the electrode slurry is applied onto the current collector, and thus it may be difficult to obtain uniformity of the electrode thickness. If such an electrode having a non-uniform thickness is used, an in-plane distribution of charge / discharge reaction occurs, making it difficult to achieve stable battery performance. On the other hand, if the spinnability exceeds the above range, dripping easily occurs when the electrode slurry is applied onto the current collector, and it becomes difficult to obtain an electrode with stable quality. Therefore, if the spinnability is within the above range, the occurrence of these problems can be suppressed, and it becomes easy to produce an electrode that achieves both good electrical characteristics and adhesion.

The “threadability” in the present specification is measured as follows.
First, a Zaan cup (made by Dazai Equipment Co., Ltd., Zaan Bisco City Cup No. 5) having an opening with a diameter of 5.2 mm at the bottom is prepared. With this opening closed, 40 g of electrode slurry is poured into the Zahn cup. Thereafter, when the opening is opened, the electrode slurry flows out from the opening. Here, when T ₀ when opening the _opening, the T _A when the thread of the electrode slurry is _completed, when the outflow of the electrode slurry is completed the T _B, "hauls herein “Thread property” can be obtained from the following mathematical formula (2).
Spinnability (%) = ((T _A −T ₀ ) / (T _B −T ₀ )) × 100 (2)

3. Electrode The electrode according to the present embodiment includes a current collector and a layer formed by applying and drying the electrode slurry on the surface of the current collector. Such an electrode can be manufactured by applying the aforementioned electrode slurry to the surface of an appropriate current collector such as a metal foil to form a coating film, and then drying the coating film. The electrode manufactured in this manner is formed by binding an electrode active material layer containing the above-described polymer particles (A) and an electrode active material, and optionally added optional components, on a current collector. It will be. Such an electrode has excellent binding properties between the current collector and the electrode active material layer, and also has good charge / discharge rate characteristics, which is one of electrical characteristics. Therefore, such an electrode is suitable as an electrode for an electricity storage device.

  The current collector is not particularly limited as long as it is made of a conductive material. In a lithium ion secondary battery, a current collector made of metal such as iron, copper, aluminum, nickel, and stainless steel is used. In particular, when aluminum is used for the positive electrode and copper is used for the negative electrode, the above-mentioned electrode binder is used. The effect of the slurry for an electrode manufactured using is best exhibited. As the current collector in the nickel metal hydride secondary battery, a punching metal, an expanded metal, a wire mesh, a foam metal, a mesh metal fiber sintered body, a metal plated resin plate, or the like is used. The shape and thickness of the current collector are not particularly limited, but it is preferable that the current collector has a sheet shape with a thickness of about 0.001 to 0.5 mm.

  There is no particular limitation on the method of applying the electrode slurry to the current collector. The coating can be performed by an appropriate method such as a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, a dipping method, or a brush coating method. The coating amount of the electrode slurry is not particularly limited, but the electrode active material layer formed after the liquid medium is removed preferably has a thickness of 0.005 to 5 mm, preferably 0.01 to 2 mm. It is more preferable to set it as an amount.

  There is no particular limitation on the drying method from the coated film after coating (method for removing water and optionally used non-aqueous medium); for example, drying with warm air, hot air, low humidity air; vacuum drying; (far) infrared , Drying by irradiation with an electron beam or the like. The drying speed is appropriately set so that the liquid medium can be removed as quickly as possible within a speed range in which the electrode active material layer does not crack due to stress concentration or the electrode active material layer does not peel from the current collector. Can be set.

Furthermore, it is preferable to increase the density of the electrode active material layer by pressing the current collector after drying. Examples of the pressing method include a mold press and a roll press. The density of the electrode active material layer after the press, preferably in the 1.6~2.4g / cm ^3, and more preferably to 1.7~2.2g / cm ^3.

4). Electric storage device An electric storage device can be manufactured using the electrodes as described above. The electricity storage device according to the present embodiment includes the above-described electrode, and further contains an electrolytic solution, and can be manufactured according to a conventional method using components such as a separator. As a specific manufacturing method, for example, a negative electrode and a positive electrode are overlapped via a separator, and this is wound into a battery container according to a battery shape, put into a battery container, an electrolyte is injected into the battery container, and sealing is performed. The method of doing is mentioned. The shape of the battery can be an appropriate shape such as a coin shape, a button shape, a sheet shape, a cylindrical shape, a square shape, or a flat shape.

  The electrolyte may be liquid or gel, and an electrolyte that effectively expresses the function as a battery may be selected from known electrolytes used for the electricity storage device according to the type of the electrode active material. The electrolytic solution can be a solution in which an electrolyte is dissolved in a suitable solvent.

As the electrolyte, in the lithium ion secondary battery, any conventionally known lithium salt can be used, and specific examples thereof include, for example, LiClO ₄ , LiBF ₄ , LiPF ₆ , LiCF ₃ CO ₂ , LiAsF. ₆ , LiSbF ₆ , LiB ₁₀ Cl ₁₀ , LiAlCl ₄ , LiCl, LiBr, LiB (C ₂ H ₅ ) ₄ , LiCF ₃ SO ₃ , LiCH ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, lithium of lower fatty acid carboxylate etc. can be illustrated. In a nickel metal hydride secondary battery, for example, an aqueous potassium hydroxide solution having a conventionally known concentration of 5 mol / liter or more can be used.

  The solvent for dissolving the electrolyte is not particularly limited. Specific examples thereof include carbonate compounds such as propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate; Lactone compounds such as butyl lactone; ether compounds such as trimethoxymethane, 1,2-dimethoxyethane, diethyl ether, 2-ethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran; sulfoxide compounds such as dimethyl sulfoxide, etc. One or more selected from these can be used. The concentration of the electrolyte in the electrolytic solution is preferably 0.5 to 3.0 mol / L, more preferably 0.7 to 2.0 mol / L.

5. EXAMPLES Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. “Part” and “%” in Examples and Comparative Examples are based on mass unless otherwise specified. Examples 1 to 3 and Comparative Examples 1 and 4 are specific examples in which the binder composition for an electrode of the present invention was used to produce a positive electrode. Examples 4 to 6 and 7 and Comparative Example 2 3, 5, and 6 are specific examples in which the electrode binder composition according to the present invention was used to produce a negative electrode.

5.1. Example 1
5.1.1. Preparation of Binder Composition for Electrode After the inside of an autoclave having an internal volume of about 6 L equipped with an electromagnetic stirrer was sufficiently purged with nitrogen, 2.5 L of deoxygenated pure water and 25 g of ammonium perfluorodecanoate as an emulsifier were charged. The temperature was raised to 60 ° C. while stirring at 350 rpm. Next, a mixed gas composed of 70% of the monomer vinylidene fluoride (VDF (registered trademark)) and 30% propylene hexafluoride (HFP) was charged until the internal pressure reached 20 kg / cm ² . 25 g of Freon 113 solution containing 20% of diisopropyl peroxydicarbonate as a polymerization initiator was injected using nitrogen gas to initiate polymerization. During the polymerization, a mixed gas consisting of 60.2% VDF (registered trademark) and 39.8% HFP was sequentially injected so that the internal pressure was maintained at 20 kg / cm ² to maintain the pressure at 20 kg / cm ² . Further, since the polymerization rate decreased as the polymerization progressed, the same amount of the same polymerization initiator solution as that described above was injected using nitrogen gas after 3 hours, and the reaction was continued for 3 hours. By adding 5 parts of glycidyl methacrylate (GMA) to the reaction solution and continuing the reaction for 3 hours, cooling the reaction solution and simultaneously stopping stirring and releasing the unreacted monomer and then stopping the reaction An aqueous dispersion containing 40% polymer particles was obtained. The obtained polymer particles were analyzed by ¹⁹ F-NMR and ¹ H-NMR. As a result, the mass composition ratio of each monomer was VDF (registered trademark) / HFP / GMA = 40/5/5. It was.

  Subsequently, 2 parts of 3,5,5-trimethylhexanoyl peroxyside (trade name “Perroyl 355”, manufactured by NOF Corporation, water solubility: 0.01%) was added to a 7 L separable flask, sodium lauryl sulfate 0 .1 part and 20 parts of water were stirred and emulsified. Further, 50 parts of the polymer particles prepared above were added and stirred for 16 hours. Next, after sufficiently replacing the inside of the separable flask with nitrogen, 20 parts of methyl methacrylate (MMA), 25 parts of 2-ethylhexyl acrylate (EHA) and 5 parts of methacrylic acid (MAA) were added and stirred at 40 ° C. . Then, it heated up at 75 degreeC and reacted for 3 hours, and also reacted at 85 degreeC for 2 hours. Thereafter, the reaction was stopped after cooling, and the aqueous dispersion (electrode binder composition) containing 40% of polymer particles was obtained by adjusting the pH to 7 with a 2.5N aqueous sodium hydroxide solution.

  About the aqueous dispersion of the obtained polymer particles, the particle size distribution is measured using a particle size distribution measuring apparatus (manufactured by Otsuka Electronics Co., Ltd., “FPAR-1000”) based on the dynamic light scattering method. The number average particle diameter (Da) was determined from the particle size distribution to be 330 nm.

  Further, the major axis (Rmax) and minor axis (Rmin) of ten polymer particles were measured with a transmission electron microscope (manufactured by Hitachi High-Technologies Corporation, model “H-7650”), and the average value was calculated. The major axis was 360 nm, the minor axis was 300 nm, and the ratio of the major axis to the minor axis (Rmax / Rmin) was 1.20.

  Furthermore, as a result of performing differential scanning calorimetry (DSC) on the obtained film (polymer) according to JIS K7121, the endothermic peaks are 120 ° C. (melting temperature Tm) and −5 ° C. (glass transition temperature Tg). Two were observed.

5.1.2. Preparation of slurry for electrode First, active material particles having a number average particle diameter (Db) of 0.5 μm are obtained by pulverizing commercially available lithium iron phosphate (LiFePO ₄ ) in an agate mortar and classifying with a sieve. Obtained.

Next, 1 part of the thickener (trade name “CMC1120”, manufactured by Daicel Chemical Industries, Ltd., trade name) in a biaxial planetary mixer (trade name “TK Hibismix 2P-03”, manufactured by Primix Co., Ltd.) (solid content conversion) Then, 100 parts of the active material particles, 5 parts of acetylene black and 68 parts of water were added and stirred at 60 rpm for 1 hour. Next, the electrode binder composition prepared in the above “5.1.1. Preparation of electrode binder composition” was added so that the polymer particles contained in the composition were 1 part, and further 1 hour. The paste was obtained by stirring. Water was added to the obtained paste to adjust the solid content concentration to 50%, and then the mixture was stirred at 200 rpm for 2 minutes using a stirring defoamer (trade name “Awatori Nertaro” manufactured by Shinky Co., Ltd.). The mixture was stirred and mixed at 1,800 rpm for 1.5 minutes at 800 rpm for 5 minutes and further under vacuum (about 5.0 × 10 ³ Pa) to prepare an electrode slurry.

The spinnability of the electrode slurry thus obtained was measured as follows.
First, a Zaan cup (made by Dazai Equipment Co., Ltd., Zaan Biscocity Cup No. 5) having an opening with a diameter of 5.2 mm at the bottom of the container was prepared. With the opening of the Zahn cup closed, 40 g of the electrode slurry prepared above was poured. When the opening was opened, the slurry flowed out. In this case, the time instant of opening the opening and T _0, the time continued to flow out so as to draw the yarn when the slurry flows measured visually, the time was T _A. Moreover, to continue the measurement from no longer attracted yarn was measured time T _B until no flow out electrode slurry. The measured values T ₀ , T _A and T _B were substituted into the following formula (2) to obtain the spinnability.
Spinnability (%) = ((T _A −T ₀ ) / (T _B −T ₀ )) × 100 (2)
The spinnability in the electrode slurry can be judged to be good when it is 30 to 80%.

5.1.3. Production and evaluation of electrodes and electricity storage devices 5.1.3.1. Production of Electrode (Positive Electrode) On the surface of a current collector made of an aluminum foil having a thickness of 30 μm, the electrode slurry prepared in the above “5.1.2. Preparation of electrode slurry” had a film thickness after drying of 100 μm. The mixture was uniformly applied by a doctor blade method and dried at 120 ° C. for 20 minutes. Then, the electrode (positive electrode) was obtained by pressing with a roll press so that the density of a film | membrane (active material layer) might become the value of Table 1.

5.1.3.2. Electrode evaluation (crack rate)
The produced electrode was cut out into an electrode plate having a width of 2 cm and a length of 10 cm, and the electrode plate was repeatedly bent 100 times along a round bar having a diameter of 2 mm in the width direction. The size of the crack along the round bar was visually observed and measured, and the crack rate was measured. The crack rate was defined by the following mathematical formula (3).
Crack rate (%) = {length with crack (mm) ÷ total length of electrode plate (mm)} × 100 (3)
Here, the electrode plate excellent in flexibility and adhesion tends to have a low crack rate. The crack rate is preferably 0%, but when the electrode plate group is manufactured by winding the electrode in a spiral shape through a separator, the crack rate is allowed up to 20%. However, if the crack rate is greater than 20%, the electrodes are easily cut off, making it impossible to manufacture the electrode plate group, and the productivity of the electrode plate group decreases. From this, it is considered that a good range is up to 20% as the threshold of the crack rate. The measurement results of the crack rate are also shown in Table 1.

5.1.3.3. Manufacture of counter electrode (negative electrode) Biaxial planetary mixer (product name “TK Hibismix 2P-03” manufactured by PRIMIX Corporation), 4 parts of polyvinylidene fluoride (PVDF (registered trademark)) (solid content conversion), negative electrode As active materials, 100 parts of graphite (in terms of solid content) and 80 parts of N-methylpyrrolidone (NMP) were added and stirred at 60 rpm for 1 hour. Thereafter, 20 parts of NMP was further added, and then using a stirring defoamer (product name “Awatori Nertaro” manufactured by Shinky Co., Ltd.) for 2 minutes at 200 rpm, then 5 minutes at 1,800 rpm, and further under vacuum The slurry for counter electrode (negative electrode) was prepared by stirring and mixing for 1.5 minutes at 1,800 rpm.

Next, the obtained slurry for the counter electrode (negative electrode) is uniformly applied to the surface of the current collector made of copper foil by a doctor blade method so that the film thickness after drying is 150 μm, and dried at 120 ° C. for 20 minutes. did. Then, the counter electrode (negative electrode) was obtained by pressing using a roll-press machine so that the density of a film | membrane may be 1.5 g / cm < ³ >.

5.1.3.4. Assembly of lithium ion battery cell The diameter of the counter electrode (negative electrode) manufactured in “5.1.3.3. Preparation of counter electrode (negative electrode)” in the glove box substituted with Ar so that the dew point is −80 ° C. or less. What was punched and molded to 15.95 mm was placed on a bipolar coin cell (made by Hosen Co., Ltd., trade name “HS Flat Cell”). Next, a separator made of a polypropylene porous film punched to a diameter of 24 mm (product name “Celguard # 2400” manufactured by Celgard Co., Ltd.) was placed, and after injecting 500 μL of electrolyte so that air did not enter, Place the positive electrode produced in “5.1.3.1. Production of electrode (positive electrode)” by punching and molding it to a diameter of 16.16 mm, and seal the outer body of the bipolar coin cell with a screw. By doing so, the lithium ion battery cell (electric storage device) was assembled. The electrolytic solution used was a solution in which LiPF ₆ was dissolved at a concentration of 1 mol / L in a solvent of ethylene carbonate / ethyl methyl carbonate = 1/1 (mass ratio).

5.1.3.5. Evaluation of electricity storage devices (evaluation of discharge rate characteristics)
For the electricity storage device manufactured in “5.1.3.4. Assembly of lithium ion battery cell” above, charging was started at a constant current (0.2 C), and when the voltage reached 4.2 V, the charging was continued. Charging was continued at a voltage (4.2 V), and the charging capacity at 0.2 C was measured with the charging completed (cut off) when the current value reached 0.01 C. Next, discharge was started at a constant current (0.2 C), and when the voltage reached 2.7 V, the discharge was completed (cut off), and the discharge capacity at 0.2 C was measured.

  Next, charging is started at a constant current (3C) for the same cell, and when the voltage reaches 4.2V, charging is continued at a constant voltage (4.2V). The charging capacity at 3C was measured with the time point of becoming the completion of charging (cut-off). Next, discharge was started at a constant current (3C), and when the voltage reached 2.7 V, the discharge was completed (cut off), and the discharge capacity at 3C was measured.

  Using the above measured values, the discharge rate (%) was calculated by calculating the ratio (percent%) of the discharge capacity at 3C to the discharge capacity at 0.2C. When the discharge rate is 80% or more, it can be evaluated that the discharge rate characteristics are good. The measured discharge rate values are also shown in Table 1.

  In the measurement conditions, “1C” indicates a current value at which discharge is completed in one hour after constant current discharge of a cell having a certain electric capacity. For example, “0.1 C” is a current value at which discharge is completed over 10 hours, and 10 C is a current value at which discharge is completed over 0.1 hours.

5.2. Example 2 and Comparative Examples 1 and 4
5.2.1. Preparation of Electrode Binder Composition As in Example 1, except that the composition of the monomer and the amount of emulsifier were appropriately changed in “5.1.1. Preparation of Electrode Binder Composition” in Example 1 above. Then, an aqueous dispersion containing polymer particles having the composition shown in Table 1 is prepared, and water is removed under reduced pressure or added according to the solid content concentration of the aqueous dispersion, whereby an aqueous dispersion having a solid content concentration of 40% is prepared. Got the body. The number average particle diameter measurement, the ratio calculation result of the major axis and minor axis, and DSC measurement were performed in the same manner as in Example 1 for the obtained polymer particles. The results are also shown in Table 1.

5.2.2. Preparation of electrode slurry A slurry for an electrode (positive electrode) in the same manner as in "5.1.2. Preparation of electrode slurry" in Example 1, except that the thickeners of the type and amount described in Table 1 were used. Was prepared and its spinnability was measured. The value of the spinnability is also shown in Table 1.

5.2.3. Production and Evaluation of Electrode and Electric Storage Device An electrode (positive electrode) and an electric storage device were produced and evaluated in the same manner as in Example 1 except that each material obtained above was used. The evaluation results are also shown in Table 1.

5.3. Example 3
5.3.1. Preparation of electrode binder composition The same as in Example 1 except that the composition of the monomer gas and the amount of emulsifier were changed appropriately in “5.1.1. Preparation of electrode binder composition” in Example 1 above. Then, an aqueous dispersion containing polymer particles having the composition shown in Table 1 is prepared, and water is removed under reduced pressure or added according to the solid content concentration of the aqueous dispersion, whereby an aqueous system having a solid content concentration of 40% is prepared. A dispersion was obtained. N-methylpyrrolidone (NMP) was added to the obtained aqueous dispersion, and water was removed under reduced pressure to obtain a binder composition using NMP as a dispersion medium. Table 1 shows the number average particle diameter measurement, ratio calculation result of major axis and minor axis, and result of DSC measurement performed on the obtained polymer particles.

5.3.2. Preparation of electrode slurry The number average particle diameter (Db) of 3 μm was obtained by appropriately changing the sieve opening used in “5.1.2. Preparation of electrode slurry” in Example 1 above. Material particles were prepared.

  Next, a biaxial planetary mixer (product name “TK Hibismix 2P-03” manufactured by PRIMIX Co., Ltd.) and a thickener (product name “CMC1150” manufactured by Daicel Chemical Industries, Ltd.) 10 parts (solid content conversion) 100 parts of active material particles having a number average particle diameter of 3 μm, 5 parts of acetylene black, 4 parts of the binder composition prepared in the above “5.3.1. Preparation of binder composition for electrodes” (in terms of solid content) ) And 68 parts of NMP were added and stirred at 60 rpm for 2 hours to obtain a paste. After adding NMP to the obtained paste to adjust the solid content concentration to 45%, using a stirring defoaming machine (trade name “Awatori Netaro”, manufactured by Shinky Co., Ltd.), 2 minutes at 200 rpm, 1800 rpm The mixture was stirred and mixed for 5 minutes at 1,800 rpm for 1.5 minutes under vacuum to prepare a slurry for electrodes.

5.3.3. Production and evaluation of electrode and electricity storage device A positive electrode and electricity storage device were produced in the same manner as in "5.1.3. Production and evaluation of electrode and electricity storage device" in Example 1, except that the above slurry for electrodes was used. ,evaluated. The evaluation results are also shown in Table 1.

5.4. Example 4
5.4.1. Preparation of Binder Composition for Electrode After the inside of a 7 L capacity separable flask was sufficiently purged with nitrogen, 0.5 parts of emulsifier “ADEKA rear soap SR1025” (trade name, manufactured by ADEKA Corporation), 45 parts of styrene (ST) , And 130 parts of water sequentially, and then 20 mL of a tetrahydrofuran solution containing 0.5 part of azobisisobutyronitrile, which is an oil-soluble polymerization initiator, is added, heated to 75 ° C. and reacted for 3 hours, The reaction was further carried out at 85 ° C. for 2 hours. After adding 10 parts of hydroxyethyl methacrylate (HEMA) to the reaction solution and continuing the reaction for 3 hours, the reaction solution was cooled and simultaneously stirred to obtain an aqueous dispersion containing 40% of polymer particles.

  Subsequently, 2 parts of 3,5,5-trimethylhexanoyl peroxyside (trade name “Perroyl 355”, manufactured by NOF Corporation, water solubility: 0.01%) was added to a 7 L separable flask, sodium lauryl sulfate 0 .1 part and 20 parts of water were stirred and emulsified. Further, 55 parts of the previously produced polymer particles were added and stirred for 16 hours. Next, after sufficiently replacing the inside of the separable flask with nitrogen, 30 parts of methyl methacrylate (MMA), 10 parts of 2-ethylhexyl acrylate (EHA) and 5 parts of methacrylic acid (MAA) were added, and the mixture was heated at 40 ° C. for 3 hours. The monomer component was absorbed into the polymer particles by stirring slowly. Then, it heated up at 75 degreeC and reacted for 3 hours, and also reacted at 85 degreeC for 2 hours. Then, after cooling, the reaction was stopped, and the aqueous dispersion (binder composition) containing 40% polymer particles was obtained by adjusting the pH to 7 with a 2.5N aqueous sodium hydroxide solution. The number average particle diameter measurement performed on the obtained polymer particles, the ratio calculation result of the major axis and minor axis, and DSC measurement were performed in the same manner as in Example 1. The results are also shown in Table 1.

5.4.2. Preparation of electrode slurry Next, a thickener (trade name “CMC2200”, manufactured by Daicel Chemical Industries, Ltd.) 1 part to a biaxial planetary mixer (trade name “TK Hibismix 2P-03” manufactured by PRIMIX Corporation) (In terms of solid content), 100 parts of commercially available graphite (in terms of solid content) and 68 parts of water were added as the negative electrode active material, and the mixture was stirred at 60 rpm for 1 hour. Thereafter, 2 parts (in terms of solid content) of the electrode binder composition prepared in “5.4.1. Preparation of electrode binder composition” was added, and the mixture was further stirred for 1 hour to obtain a paste. Water was added to the obtained paste to adjust the solid content to 50%, and then the mixture was stirred at 200 rpm for 2 minutes at 1800 rpm at 200 rpm using a stirring defoamer (trade name “Netaro Awatori” manufactured by Shinky Co., Ltd.). The mixture was stirred and mixed for 5 minutes at 1,800 rpm for 1.5 minutes under vacuum to prepare a slurry for electrodes. The spinnability of the negative electrode slurry was measured by the method described in “5.1.2. Preparation of electrode slurry” in Example 1. The results are also shown in Table 1.

5.4.3. Manufacture and evaluation of electrodes and electricity storage devices 5.4.3.1. Production of Electrode (Negative Electrode) The electrode (negative electrode) slurry prepared in the above “5.4.2. Preparation of electrode slurry” on the surface of a current collector made of 20 μm thick copper foil was dried. Was uniformly applied by a doctor blade method so as to be 150 μm, and dried at 120 ° C. for 20 minutes. Then, the electrode (negative electrode) was obtained by pressing using a roll-press machine so that the density of a film | membrane may be 1.5 g / cm < ³ >.

5.4.3.2. Evaluation of Crack Rate of Negative Electrode The crack rate of the negative electrode was measured in the same manner as in “5.1.3.2. Electrode Evaluation (Crack Rate)” in Example 1. The results are also shown in Table 1.

5.4.3.3. Manufacture of counter electrode (positive electrode) Biaxial planetary mixer (product name "TK Hibismix 2P-03" manufactured by PRIMIX Corporation) and binder for electrochemical device electrode (product name "KF polymer # 1120" manufactured by Kureha Corporation) ) 4.0 parts (in terms of solid content), 3.0 parts of conductive assistant (manufactured by Denki Kagaku Kogyo Co., Ltd., trade name “Denka Black 50% pressed product”), LiCoO _{2 having a} particle size of 5 μm as a positive electrode active material (Hayashi 100 parts (made by Kasei Co., Ltd.) (solid content conversion) and 36 parts of N-methylpyrrolidone (NMP) were added and stirred at 60 rpm for 2 hours. After adding NMP to the obtained paste to adjust the solid content to 65%, using a stirring defoaming machine (trade name “Awatori Netaro”, manufactured by Shinky Co., Ltd.), 2 minutes at 200 rpm, 1800 rpm The slurry for positive electrode was prepared by stirring and mixing for 5 minutes at 1800 rpm for 1 minute at 1800 rpm. The obtained positive electrode slurry was uniformly applied to the surface of a current collector made of aluminum foil by a doctor blade method so that the film thickness after drying was 80 μm, followed by drying treatment at 120 ° C. for 20 minutes. Then, the positive electrode for secondary batteries was obtained by pressing with a roll press so that the density of an electrode layer may be 3.0 g / cm < ³ >.

5.4.3.4. Assembly of Lithium Ion Battery Cell A lithium ion battery cell was assembled in the same manner as in “5.1.3.4. Assembly of lithium ion battery cell” in Example 1.

5.4.3.5. Evaluation of electricity storage devices (evaluation of discharge rate characteristics)
The electricity storage device was evaluated in the same manner as in “5.1.3.5. Evaluation of electricity storage device (evaluation of discharge rate characteristics)” in Example 1. The results are also shown in Table 1.

5.5. Examples 5, 6, 7 and Comparative Examples 2, 3, 5, 6
5.5.1. Preparation of Binder Composition for Electrode For Examples 5 and 6 and Comparative Examples 2, 3, 5, and 6, in “5.4. 1. Preparation of Binder Composition for Electrode” in Example 4 above, An aqueous dispersion containing polymer particles having the composition shown in Table 1 was prepared in the same manner as in Example 4 except that the composition and the amount of the emulsifier were appropriately changed, and water was added according to the solid content concentration of the aqueous dispersion. Was removed or added under reduced pressure to obtain an aqueous dispersion having a solid content of 40%. The number average particle diameter measurement, the ratio calculation result of the major axis and the minor axis, and DSC measurement were performed in the same manner as Example 4 for the obtained polymer particles. The results are also shown in Table 1.
For Example 7, the electrode binder composition prepared in “5.1.1. Preparation of Electrode Binder Composition” in Example 1 above was used.

5.5.2. Preparation of slurry for electrode (negative electrode) The same procedure as in “5.4.2. Preparation of slurry for electrode (negative electrode)” in Example 4 was used, except that the type and amount of thickener described in Table 1 were used. An electrode (negative electrode) slurry was prepared and its spinnability was measured. The results are also shown in Table 1.

5.5.3. Production and Evaluation of Electrode (Negative Electrode) and Electric Storage Device An electrode (negative electrode) and an electric storage device were produced and evaluated in the same manner as in Example 4 except that each material obtained above was used. The results are also shown in Table 1.

Abbreviations of each component in Table 1 are as follows.
<Fluorine-containing compounds>
-VDF (registered trademark): vinylidene fluoride-HFP: propylene hexafluoride-TFE: tetrafluoroethylene <polyfunctional (meth) acrylic acid ester>
AMA: allyl methacrylate GMA: glycidyl methacrylate HEMA: hydroxyethyl methacrylate <unsaturated carboxylic acid>
AA: acrylic acid MAA: methacrylic acid <monofunctional (meth) acrylic ester>
-MMA: methyl methacrylate-EHA: 2-ethylhexyl acrylate <other monomer>
・ AN: Acrylonitrile ・ ST: Styrene ・ BD: Butadiene <Active material>
LFP: lithium iron phosphate (LiFePO ₄ )
・ GF: Graphite

  CMC1120, CMC1150, CMC2200, and CMC2280 described in the thickener column are all trade names of Daicel Chemical Industries, Ltd., and are alkali metal salts of carboxymethylcellulose.

  The notation “-” in Table 1 indicates that the corresponding component was not used or the corresponding operation was not performed.

5.6. Evaluation results As is apparent from Table 1 above, the electrode slurry prepared using the electrode binder composition according to the present invention shown in Examples 1 to 7 was formed between the current collector and the active material layer. An electrode having good binding properties, a low crack rate, and excellent adhesion was provided. Moreover, the electrical storage device (lithium ion battery) provided with these electrodes had good discharge rate characteristics.

  The present invention is not limited to the above-described embodiments, and various modifications can be made. For example, the present invention includes substantially the same configuration (for example, a configuration having the same function, method, and result, or a configuration having the same purpose and effect) as the configuration described in the embodiment. In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that achieves the same effect as the configuration described in the embodiment or a configuration that can achieve the same object. In addition, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

10a, 10b, 10c: polymer particles, 20a, 20b, 20c, 20d, 20e, 20f ... irregularly shaped particles, 22, 22a, 22b, 22c, 22d, 22e, 22f ... first polymer particles, 23 ... second Monomer for polymer particles, 24, 24a, 24b, 24c, 24d, 24e, 24f ... second polymer particles

Claims (11)

Polymer particles (A) having a number average particle diameter in the range of 50 to 400 nm;
A dispersion medium (B);
Containing
A binder composition for an electrode, wherein a ratio (Rmax / Rmin) of a major axis (Rmax) to a minor axis (Rmin) of the polymer particles (A) is in a range of 1.1 to 1.5. The polymer particles (A) are
A repeating unit (a) derived from a fluorine-containing compound;
A repeating unit (b) derived from a polyfunctional (meth) acrylic acid ester;
The binder composition for electrodes according to claim 1 containing at least.   The quantity ratio of the monomer constituting the repeating unit (a) and the monomer constituting the repeating unit (b) is in the range of 2: 1 to 10: 1 on a mass basis. The binder composition for electrodes as described.   The binder composition for electrodes according to claim 2 or 3, which is used for producing a positive electrode of an electricity storage device. The polymer particles (A) are
A repeating unit (c) derived from an unsaturated carboxylic acid;
A repeating unit (b) derived from a polyfunctional (meth) acrylic acid ester;
The binder composition for electrodes according to claim 1 containing at least.   The quantity ratio of the monomer constituting the repeating unit (c) and the monomer constituting the repeating unit (b) is in the range of 1: 1 to 1: 3 on a mass basis. The binder composition for electrodes as described in 2.   The binder composition for electrodes according to claim 5 or 6, which is used for producing a negative electrode of an electricity storage device.   When differential scanning calorimetry (DSC) was performed on the polymer particles (A) according to JIS K7121, one endothermic peak in the temperature range of -30 ° C to 30 ° C and a temperature of 80 ° C to 150 ° C The electrode binder composition according to any one of claims 1 to 7, wherein one endothermic peak in the range is observed.   The electrode slurry containing the binder composition for electrodes as described in any one of Claims 1 thru | or 8, and an electrode active material.   An electrode for an electrical storage device, comprising: a current collector; and an electrode active material layer produced by applying and drying the electrode slurry according to claim 9 on a surface of the current collector.   An electricity storage device comprising the electrode for an electricity storage device according to claim 10.

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