JP5348444B1 - Binder composition for power storage device, slurry for power storage device electrode, power storage device electrode, slurry for protective film formation, protective film, and power storage device - Google Patents

Abstract

  The binder composition for an electricity storage device according to the present invention is a polymer particle (A) containing a repeating unit (a) derived from a fluorine-containing compound and a repeating unit (b) derived from a polyfunctional (meth) acrylic ester, An endothermic peak in a temperature range of −30 ° C. to 30 ° C. when differential scanning calorimetry (DSC) is performed on the polymer particles (A) according to JIS K7121. And one endothermic peak in the temperature range of 80 ° C. to 150 ° C. are observed.

Description

  The present invention includes a power storage device binder composition, a power storage device electrode slurry containing the binder composition and an active material, a power storage device electrode formed by applying the slurry to a current collector, and the electrode The present invention relates to a power storage device, a slurry for forming a protective film containing the binder composition and inorganic particles, a protective film formed from the slurry, and a power storage device including the protective film.

  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.

  An electricity storage device electrode 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 onto a current collector surface. The properties required for the polymer particles used as the binder for the electrode include the bonding between the active material particles and the binding 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 oxidation resistance, such as polyvinylidene fluoride. 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 oxidation resistance have been proposed.

  For example, Japanese Patent Application Laid-Open No. 2011-3529 proposes a technique for achieving both the oxidation resistance and adhesion of a negative electrode binder by using polyvinylidene fluoride and a rubber-based polymer in combination. Japanese Patent Application Laid-Open No. 2010-55847 improves the adhesion by dissolving polyvinylidene fluoride in a specific organic solvent, coating it on the current collector surface, and then removing the solvent at a low temperature. Techniques to do so have been proposed. Furthermore, Japanese Patent Application Laid-Open No. 2002-42819 proposes a technique for improving the 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. Has been. Furthermore, JP 2000-299109 A discloses a technique for improving the above characteristics by controlling the binder composition, and JP 2010-205722 A and JP 2010-3703 A have an epoxy group or a hydroxyl group. Techniques for improving the above characteristics using a binder have been studied.

  On the other hand, in order to achieve downsizing of the electricity storage device, it is also essential to make a thin film such as a separator that separates the positive electrode and the negative electrode. However, when the space between the positive electrode and the negative electrode is narrowed due to the miniaturization of the electricity storage device, there is a problem that a short circuit easily occurs. In particular, in an electricity storage device using metal ions such as lithium ions, dendrites due to metal ions are likely to occur on the electrode surface by repeated charge and discharge. Such dendrites usually precipitate as needle-like crystals, so that they tend to grow through the separator, which is a porous film. When the dendrite grows through the separator and reaches the surface of the counter electrode, the electricity storage device is short-circuited and loses the charge / discharge function.

  As the thickness of the separator is reduced and the distance between the positive electrode and the negative electrode is reduced, the risk of occurrence of such a phenomenon increases, and the reliability decreases accordingly. In order to avoid such a phenomenon, in WO 2009/041395 pamphlet and JP 2009-87562 A, a porous layer containing a resin binder containing polyamide, polyimide and polyamideimide is formed on a porous separator substrate. A technique for improving the battery characteristics by forming them has been studied. Japanese Patent Application Laid-Open No. 2009-54455 improves battery characteristics by forming a porous protective film including a binder containing a fluorine-based resin and a rubber-based resin on at least one surface of a positive electrode and a negative electrode. Technology is being considered.

  However, according to the technique described in JP2011-3529 in which a fluorine-containing organic polymer and a rubber-based polymer are used in combination, the adhesion is improved, but the oxidation resistance of the organic polymer 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 technique described in Japanese Patent Application Laid-Open Nos. 2010-55847 and 2002-42819 using only a fluorine-containing organic polymer as an electrode binder, the level of adhesion is still insufficient. . In addition, the binder composition described in JP 2000-299109 A, JP 2010-205722 A, and JP 2010-3703 A improves the adhesion, but the binder itself attached to the active material itself. Becomes a resistance component of the electrode, and it has been difficult to maintain good charge / discharge characteristics over a long period of time.

  On the other hand, according to the materials described in International Publication No. 2009/041395 pamphlet, Japanese Unexamined Patent Application Publication No. 2009-87562 and Japanese Unexamined Patent Application Publication No. 2009-54455, by forming a protective film on the separator or electrode surface Although a short circuit caused by dendrite generated along with charging / discharging can be suppressed, the permeability and liquid retention of the electrolytic solution are lowered, so that lithium ions are prevented from being adsorbed to and desorbed from the active material. As a result, there is a problem that the internal resistance of the electricity storage device increases and the charge / discharge characteristics are deteriorated.

  Accordingly, some embodiments according to the present invention provide a binder composition for an electricity storage device capable of producing an electricity storage device having excellent adhesion and excellent charge / discharge characteristics by solving at least a part of the above problems. To do.

  Further, some aspects of the present invention provide a protective film that solves at least a part of the above-described problems, and is excellent in electrolyte permeability and liquid retention, and can suppress an increase in internal resistance of the electricity storage device, The present invention provides a slurry for producing the protective film and an electricity storage device provided with the protective film.

  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 an electricity storage device according to the present invention is:
An electricity storage device comprising polymer particles (A) containing a repeating unit (a) derived from a fluorine-containing compound and a repeating unit (b) derived from a polyfunctional (meth) acrylate, and a liquid medium (B) In binder composition for
When differential scanning calorimetry (DSC) was performed on the polymer particles (A) in accordance with 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 is observed.

[Application Example 2]
In the binder composition for an electricity storage device of Application Example 1,
The amount ratio of the repeating unit (a) and the repeating unit (b) in the polymer particles (A) may be in the range of 2: 1 to 10: 1 on a mass basis.

[Application Example 3]
In the binder composition for an electricity storage device of Application Example 1 or Application Example 2,
The number average particle diameter of the polymer particles (A) may be in the range of 50 to 400 nm.

[Application Example 4]
In the binder composition for an electricity storage device according to any one of Application Examples 1 to 3,
The ratio (Rmax / Rmin) of the major axis (Rmax) to the minor axis (Rmin) of the polymer particles (A) may be in the range of 1.1 to 1.5.

[Application Example 5]
In the binder composition for an electricity storage device according to any one of Application Examples 1 to 4,
The polymer particle (A) further includes a repeating unit (c) derived from an unsaturated carboxylic acid, and the repeating unit derived from the fluorine-containing compound (a) with respect to 100 parts by mass of the polymer particle (A) (a ) 5-50 parts by mass and 1-10 parts by mass of the repeating unit (c) derived from the unsaturated carboxylic acid.

[Application Example 6]
The binder composition for an electricity storage device according to any one of Application Example 1 to Application Example 5,
It can be used for the purpose of producing a positive electrode of an electricity storage device.

[Application Example 7]
One aspect of the slurry for the electricity storage device electrode according to the present invention is:
It contains the binder composition for electrical storage devices of any one example of the application example 1 thru | or the application example 6, and an active material, It is characterized by the above-mentioned.

[Application Example 8]
One aspect of the electricity storage device electrode according to the present invention is:
It is characterized by comprising: a current collector; and an active material layer produced by applying and drying the electricity storage device electrode slurry of Application Example 7 on the surface of the current collector.

[Application Example 9]
One aspect of the slurry for forming a protective film according to the present invention is:
It contains the binder composition for electrical storage devices of any one example of the application example 1 thru | or the application example 5, and an inorganic particle.

[Application Example 10]
In the protective film-forming slurry of Application Example 9,
The inorganic particles may be at least one particle selected from the group consisting of silica, titanium oxide, aluminum oxide, zirconium oxide, and magnesium oxide.

[Application Example 11]
One aspect of the protective film according to the present invention is:
It is produced using the protective film-forming slurry of Application Example 9 or Application Example 10.

[Application Example 12]
One aspect of the electricity storage device according to the present invention is:
The power storage device electrode according to Application Example 8 is provided.

[Application Example 13]
One aspect of the electricity storage device according to the present invention is:
The protective film of Application Example 11 is provided.

[Application Example 14]
In the electricity storage device of Application Example 13,
A positive electrode and a negative electrode may be further provided, and the protective film may be in contact with at least one surface of the positive electrode and the negative electrode.

[Application Example 15]
In the electricity storage device of Application Example 14,
A separator disposed between the positive electrode and the negative electrode can be further provided.

[Application Example 16]
In the electricity storage device of Application Example 13,
A positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode may be further provided, and a surface of the separator may be covered with the protective film.

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

  According to the electricity storage device provided with the protective film produced using the binder composition for an electricity storage device according to the present invention, it is excellent in electrolyte permeability and liquid retention, and it is possible to suppress an increase in internal resistance. That is, the power storage device according to the present invention has excellent charge / discharge characteristics because the degree of increase in the internal resistance of the power storage device is small even after repeated charge / discharge or overcharge. In addition, since the said protective film is arrange | positioned between a positive electrode and a negative electrode, it can also suppress the short circuit resulting from the dendride which generate | occur | produces with charging / discharging. Since the binder composition for an electricity storage device according to the present invention is further excellent in oxidation resistance, it can be particularly suitably used for forming a protective film facing the positive electrode of the electricity storage device.

FIG. 1 is an explanatory view schematically showing the concept of the major axis and the minor axis of the polymer particles (A). FIG. 2 is an explanatory view schematically showing the concept of the major axis and the minor axis of the polymer particles (A). FIG. 3 is an explanatory view schematically showing the concept of the major axis and the minor axis of the polymer particles (A). FIG. 4 is an explanatory view schematically showing the concept of irregularly shaped particles. FIG. 5 is an explanatory diagram schematically showing the concept of irregularly shaped particles. FIG. 6 is an explanatory view schematically showing the concept of irregularly shaped particles. FIG. 7 is an explanatory view schematically showing the concept of irregularly shaped particles. FIG. 8 is an explanatory view schematically showing the concept of irregularly shaped particles. FIG. 9 is an explanatory view schematically showing the concept of irregularly shaped particles. FIG. 10 is an explanatory view schematically showing the generation mechanism of irregularly shaped particles. FIG. 11 is an explanatory view schematically showing the generation mechanism of irregularly shaped particles. FIG. 12 is an explanatory view schematically showing the generation mechanism of irregularly shaped particles. FIG. 13 is a schematic diagram illustrating a cross section of the electricity storage device according to the first specific example. FIG. 14 is a schematic diagram illustrating a cross section of the electricity storage device according to the second specific example. FIG. 15 is a schematic diagram illustrating a cross section of an electricity storage device according to a third specific example.

  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. Binder composition for an electricity storage device The binder composition for an electricity storage device according to the present embodiment includes a repeating unit (a) derived from a fluorine-containing compound and a repeating unit (b) derived from a polyfunctional (meth) acrylate. When the polymer particle (A) and the liquid medium (B) are contained, and the polymer particle (A) is subjected to differential scanning calorimetry (DSC) in accordance with JIS K7121, the temperature ranges from −30 ° C. One endothermic peak in the temperature range of 30 ° C. and one endothermic peak in the temperature range of 80 ° C. to 150 ° C. are observed. The binder composition for an electricity storage device according to the present embodiment is present in a latex state in which the polymer particles (A) are dispersed in the liquid medium (B).

  In addition, the binder composition for an electricity storage device according to the present embodiment is a binder for an electricity storage device electrode for improving the binding ability between active material particles, the adhesion adhesion between the active material particles and the current collector, and the powder fall resistance. It can be used as a composition (hereinafter referred to as “binder composition for electrodes” when used in this application), or a protective film for suppressing a short circuit caused by dendrid that occurs during charge and discharge. It can also be used as a binder composition for formation. Hereafter, each component contained in the binder composition for electrical storage devices 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 binder composition for an electricity storage device according to this embodiment have a number average particle diameter (Da) in the range of 50 to 400 nm. It is preferable that it is in the range of 100 to 250 nm. When the number average particle diameter of the polymer particles (A) is in the above range, the polymer particles can be sufficiently adsorbed on the surfaces of the active material particles and inorganic particles as described later. With the movement of the polymer particles, the polymer particles can also follow and move. As a result, since only one of the particles can be prevented from migrating alone, deterioration of electrical characteristics can be reduced.

  The number average particle diameter (Da) of the polymer particles (A) is a particle size distribution measured using a particle size distribution measuring apparatus based on the light scattering method, and the number of particles when 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 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 (A) contained in the binder composition for an electricity storage device. In addition, the number average particle diameter (Da) of the polymer particles (A) is obtained by centrifuging a slurry for forming an electricity storage device electrode and a slurry for forming a protective film, which will be described later, to precipitate active material particles, It can also be measured by a method of measuring with a particle size distribution measuring apparatus.

  The polymer particles (A) contained in the binder composition for an electricity storage device according to the present embodiment have a ratio (Rmax / Rmin) of the major axis (Rmax) to the minor axis (Rmin) of 1.1 to 1.5. Is preferably in the range of 1.2 to 1.4. When the ratio (Rmax / Rmin) is in the above range, the surface area of the polymer particles (A) increases and the surface of the polymer particles (A) is not a true spherical surface. In addition, the bonding ability between the inorganic particles, the adhesion ability between the current collector and the active material layer, and the adhesion ability between the protective film and the electrode or the separator are improved. As a result, the electrical characteristics of the electricity storage device are improved.

  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 shortest diameter among 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) are preferably “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. 4 to 9.

  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 a structure in which the deformed particle 20c shown in FIG. 6 has an oval shape like a rugby ball as a whole. 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).

1.1.2. The repeating unit which comprises polymer particle (A) The binder composition for electrical storage devices which concerns on this Embodiment is the repeating unit derived from the repeating unit (a) derived from a fluorine-containing compound, and polyfunctional (meth) acrylic acid ester The polymer particle (A) containing (b) is included. Hereinafter, the repeating unit which comprises a polymer particle (A) is demonstrated.

1.1.2.1. Repeating unit derived from fluorine-containing compound (a)
The polymer particles (A) 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. Examples of the fluorine-containing compound having an ethylenically unsaturated bond include an olefin compound having a fluorine atom and a (meth) acrylic acid ester having a fluorine atom. Examples of the olefin compound having a fluorine atom include vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, ethylene trifluoride chloride, and perfluoroalkyl vinyl ether. As the (meth) acrylic acid ester having a fluorine atom, for example, a compound represented by the following general formula (1), (meth) acrylic acid 3 [4 [1-trifluoromethyl-2,2-bis [bis (tri Fluoromethyl) fluoromethyl] ethynyloxy] benzooxy] 2-hydroxypropyl and the like.

（一般式（１）中、Ｒ^１は水素原子またはメチル基であり、Ｒ^２はフッ素原子を含有する炭素数１〜１８の炭化水素基である。）

(In the general formula (1), R ¹ is a hydrogen atom or a methyl group, and R ² is a C 1-18 hydrocarbon group containing a fluorine atom.)

Examples of R ² in the general formula (1) include a fluorinated alkyl group having 1 to 12 carbon atoms, a fluorinated aryl group having 6 to 16 carbon atoms, and a fluorinated aralkyl group having 7 to 18 carbon atoms. It is preferably a fluorinated alkyl group having 1 to 12 carbon atoms. Preferable specific examples of R ^{2 in} the general formula (1) include, for example, 2,2,2-trifluoroethyl group, 2,2,3,3,3-pentafluoropropyl group, 1,1,1, 3,3,3-hexafluoropropan-2-yl group, β- (perfluorooctyl) ethyl group, 2,2,3,3-tetrafluoropropyl group, 2,2,3,4,4,4- Hexafluorobutyl group, 1H, 1H, 5H-octafluoropentyl group, 1H, 1H, 9H-perfluoro-1-nonyl group, 1H, 1H, 11H-perfluoroundecyl group, perfluorooctyl group, etc. Can do. Of these, the fluorine-containing compound having an ethylenically unsaturated bond is preferably an olefin compound having a fluorine atom, and is at least one selected from the group consisting of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene. It is particularly preferred. Only 1 type may be used for the said fluorine-containing compound which has an ethylenically unsaturated bond, and 2 or more types may be mixed and used for it. When the polymer particles (A) have the repeating unit (a), the oxidation resistance of the polymer particles tends to be good.

  The binder composition for an electricity storage device according to the present embodiment can be used for producing any of the positive electrode, the negative electrode, and the protective film, but from the viewpoint of imparting good oxidation resistance, It can be suitably used as a binder composition for forming a protective film or a binder composition for forming a protective film. This is because, when polymer particles having low oxidation resistance are used in the positive electrode or the protective film 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 to 50 parts by mass with respect to 100 parts by mass of the polymer particles (A). preferable.

1.1.2.2. Repeating unit (b) derived from polyfunctional (meth) acrylic acid ester
The polymer particles (A) 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 shows having a functional group.

  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 ground contact area between the particles becomes small, so the first polymer particles and the second polymer particles may not be in close contact, and irregularly shaped particles may not be produced. On the other hand, when 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 the irregularly shaped particle may not be produced.

  The polymer particles (A) preferably have a quantitative ratio of the repeating unit (a) to the repeating unit (b) in the range of 2: 1 to 10: 1 on a mass basis. More preferably, it is in the range of 9: 1. 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 further contain a repeating unit (c) derived from an unsaturated carboxylic acid. When the polymer particles (A) have a structural unit (c) derived from an unsaturated carboxylic acid, a slurry for an electricity storage device electrode and a slurry for forming a protective film using the binder composition for an electricity storage device according to the present embodiment (Hereinafter, these are collectively referred to simply as “slurry”), and the stability is improved.

  Specific examples of the unsaturated carboxylic acid include mono- or dicarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, and one or more selected from these. Can be. 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, and it is especially preferable that it is 1-10 mass parts. 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 slurry preparation, 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 repeating unit (d) derived from a monofunctional (meth) acrylic acid ester compound, the obtained polymer particle (A) has an appropriate affinity for the electrolytic solution. In addition, while suppressing an increase in internal resistance due to the binder becoming an electrical resistance component in the electricity storage device, it is possible to prevent a decrease in adhesion 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. Of these, one or more selected from methyl (meth) acrylate, ethyl (meth) acrylate and 2-ethylhexyl (meth) acrylate is preferable, and methyl (meth) acrylate is particularly preferable. 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 a raise of resistance, the fall of adhesiveness by absorbing electrolyte excessively can be prevented.

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 particles (A) may further contain a repeating unit (f) derived from a conjugated diene compound. 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. The content rate of the repeating unit (f) in a polymer particle (A) can be 35 mass parts or less with respect to 100 mass parts of polymer particles (A).

1.1.2.7. Repeating units derived from aromatic vinyl compounds (g)
The polymer particles (A) may further contain a repeating unit (g) derived from an aromatic vinyl compound. Specific examples of the aromatic vinyl compound include styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, chlorostyrene, divinylbenzene and the like. The content rate of the repeating unit (g) in a polymer particle (A) can be 50 mass parts or less with respect to 100 mass parts of polymer particles (A).

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 An amino acid amide of ethylenically unsaturated carboxylic acid such as aminoethyl acrylamide, dimethylaminomethyl methacrylamide, methylaminopropyl methacrylamide, etc., and one or more selected from these be able to.

1.1.3. Characteristics of polymer particles (A) 1.1.3.1. Thermal characteristics of polymer particles (A) When the above polymer particles (A) are measured by differential scanning calorimetry (DSC) in accordance with JIS K7121, an endothermic peak in the temperature range of -30 ° C to 30 ° C is observed. One and one endothermic peak in the temperature range of 80 ° C. to 150 ° C. are observed. When two endothermic peaks are observed in this way, it is understood that there are at least two transition temperatures in the polymer particles (A). When one temperature of the endothermic peak of the polymer particles (A) is in the range of −30 to + 30 ° C., when used as a binder composition for an electrode, the particles are better than the active material layer. Flexibility and tackiness can be imparted, and therefore adhesion can be further improved. On the other hand, when used as a binder composition for forming a protective film, the particles can impart good flexibility and tackiness to the protective film, and therefore the adhesion can be further improved.

  In general, in an electricity storage device, the temperature rises during charging and discharging, and may be locally heated to near 80 ° C. In such a case, if the other temperature of the endothermic peak of the polymer particles (A) is less than the above range, the polymer may be deteriorated, so that stable charge / discharge characteristics cannot be achieved. On the other hand, it is necessary to sufficiently remove the dispersion medium in the step of producing a slurry for an electricity storage device electrode using the binder composition for an electrode and applying the slurry to a current collector to produce an electrode. It is common to dry by heating to about 150 ° C. Moreover, when forming a protective film, it is common to perform the drying process of a coating film on the same conditions. At this time, if any phase change occurs in the polymer particles, the wettability of the contact surface between the active material or inorganic particle surface and the polymer particles changes, and the polymer particles can be bonded more firmly. Therefore, when another temperature of the endothermic peak of the polymer particles (A) is in the range of 80 ° C. to 150 ° C., the binding capacity between the active material or inorganic particles and the polymer particles can be improved, and the electricity storage device Deterioration of the polymer during use can be effectively prevented.

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 THF insoluble content is the said range, even when an electrical storage device is produced and charging / discharging is repeated over a long period of time, elution of the polymer particle (A) to electrolyte solution can be suppressed.

1.1.4. Method for producing polymer particles (A) The polymer particles (A) contained in the binder composition for an electricity storage device according to the present embodiment have a particularly limited synthesis method as long as the polymer particles (A) have the above-described configuration. However, it can be easily synthesized by, for example, a known emulsion polymerization process or a suitable combination thereof. For example, it can be produced by the method described in JP-A-2007-197588.

  Specifically, the polymer particles (A) contained in the binder composition for an electricity storage device according to the present embodiment can be produced according to the method described below. 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, as the initiator, persulfates such as potassium persulfate and ammonium persulfate; diisopropyl peroxydicarbonate, benzoyl peroxide, lauroyl peroxide, tert-butylperoxy-2 Organic peroxides such as ethylhexanoate; azo compounds such as azobisisobutyronitrile, dimethyl-2,2′-azobisisobutyrate, 2-carbamoylazaisobutyronitrile; having a peroxide group A redox system in which a reducing agent such as a radical emulsifier containing a radical emulsifying compound, sodium hydrogen sulfite, and ferrous sulfate is combined can be used.

  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.

  Examples of the emulsifier used in the emulsion polymerization include an anionic surfactant, a nonionic surfactant, an amphoteric surfactant, and a fluorosurfactant. In addition, you may use the reactive emulsifier etc. which have an unsaturated double bond in a molecule | numerator.

  Examples of the anionic surfactant include sulfates of higher alcohols, alkylbenzene sulfonates, aliphatic sulfonates, sulfates of polyethylene glycol alkyl ethers, etc .; examples of the nonionic surfactants include polyethylene glycol Examples thereof include alkyl esters, alkyl ethers of polyethylene glycol, alkyl phenyl ethers of polyethylene glycol, and the like.

  As the amphoteric surfactant, for example, the anion portion is composed of carboxylate, sulfate ester salt, sulfonate salt or phosphate ester salt, and the cation portion is composed of amine salt, quaternary ammonium salt or the like. Things can be mentioned. Specific examples of such amphoteric surfactants include betaine compounds such as lauryl betaine and stearyl betaine; surface activity of amino acid types such as lauryl-β-alanine, lauryl di (aminoethyl) glycine, octyldi (aminoethyl) glycine, and the like. An agent can be mentioned.

  Examples of the fluorosurfactant include fluorobutyl sulfonate, phosphoric acid ester having a fluoroalkyl group, carboxylate having a fluoroalkyl group, and a fluoroalkylethylene oxide adduct. Examples of such commercially available fluorosurfactants include F-top EF301, EF303, EF352 (above, manufactured by Tochem Products Co., Ltd.); Megafac F171, F172, F173 (above, manufactured by DIC Corporation); FC430, FC431 (above, manufactured by Sumitomo 3M Limited); Asahi Guard AG710, Surflon S-381, S-382, SC101, SC102, SC103, SC104, SC105, SC106, Surfinol E1004, KH-10, KH-20, KH-30, KH-40 (above, manufactured by Asahi Glass Co., Ltd.); Footents 250, 251, 222F, FTX-218 (above, manufactured by Neos Co., Ltd.), and the like. As an emulsifier, the 1 type (s) or 2 or more types selected from the above can be 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. Liquid medium (B)
The binder composition for an electricity storage device according to the present embodiment contains a liquid medium (B). The liquid 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 binder composition for an electricity storage device 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. Increases the nature.

1.3. Other additives The binder composition for an electricity storage device according to the present embodiment may further contain other additives as necessary in addition to the polymer particles (A) and the liquid medium (B) described above. it can. 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 Corporation) as alkali metal salts of carboxymethyl cellulose.

  When the binder composition for an electricity storage device according to the present embodiment contains a thickener, the use ratio of the thickener is preferably 15% by mass with respect to the total solid content in the binder composition for an electricity storage device. It is below, More preferably, it is 0.1-10 mass%.

2. Power storage device electrode slurry The power storage device electrode slurry according to the present embodiment can be produced using the power storage device binder composition described above. The slurry for an electricity storage device electrode refers to a dispersion used to form an active material layer on the surface of the current collector after being applied to the surface of the current collector and then dried. The slurry for an electricity storage device electrode according to the present embodiment contains the aforementioned binder composition for an electricity storage device, an active material, and water. Hereinafter, each component contained in the slurry for an electricity storage device electrode according to the present embodiment will be described in detail. However, the components contained in the binder composition for an electricity storage device are omitted because they are as described above.

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

For example, when producing a positive electrode of a lithium ion secondary battery, the positive electrode active material is not particularly limited as long as it is a positive electrode material that can be doped / undoped with lithium and contains a sufficient amount of lithium. An 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 (2) and having an olivine type crystal structure.
Li _1-x M _x (XO ₄ ) (2)
(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 depending on the valence of M and (XO ₄ ), the formula (2 ) The overall valence is selected to be zero, and satisfies the relationship 0 <x <1.)

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.

  On the other hand, when producing the negative electrode of a lithium ion secondary battery, as a negative electrode active material, a carbon material, a crystalline or an amorphous metal oxide etc. can be used suitably, for example. Examples of carbon materials include non-graphitizable carbon materials such as coke and glassy carbon, and graphites of highly crystalline carbon materials having a developed crystal structure. Specifically, pyrolytic carbons, cokes ( Pitch coke, needle coke, petroleum coke, etc.), graphite, glassy carbons, polymer compound fired bodies (phenol resins, furan resins, etc. fired and carbonized at an appropriate temperature), carbon fibers, activated carbon, etc. Can be mentioned. Examples of crystalline or amorphous metal oxides include magnesium (Mg), boron (B), aluminum (Al), gallium (Ga), indium (In), silicon (Si), germanium (Ge), tin (Sn ), Lead (Pb), bismuth (Bi), cadmium (Cd), silver (Ag), zinc (Zn), hafnium (Hf), zirconium (Zr), yttrium (Y), palladium (Pd) or platinum (Pt) ) As a constituent element. In particular, those containing silicon (Si) or tin (Sn) as constituent elements can be suitably used.

  When the active material is a positive electrode active material, the number average particle diameter (Db) of the 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 (Db) of the positive electrode active material is within the above range, the diffusion distance of lithium in the positive electrode active material is shortened, so that the resistance associated with lithium desorption / insertion during charge / discharge can be reduced. As a result, the charge / discharge characteristics are further improved. Further, when the slurry for the electricity storage device electrode contains a conductivity-imparting agent described later, the contact area between the cathode active material and the conductivity-imparting agent is sufficient because the average particle diameter (Db) of the cathode active material is within the above range. Therefore, the electronic conductivity of the electrode is improved, and the electrode resistance is further reduced.

  When the active material is a negative electrode active material, the number average particle diameter (Db) of the active material is preferably in the range of 1 to 50 μm, more preferably in the range of 5 to 40 μm, and 10 to 30 μm. It is especially preferable that it is in the range. When the number average particle diameter (Db) of the negative electrode active material is in the above range, the aggregation of the negative electrode active material particles in the negative electrode slurry can be suppressed, and the negative electrode active material layer has a uniform distribution of the negative electrode active material particles. Since the fabrication becomes easy, the power storage characteristics of the power storage device can be improved.

  Here, the number average particle diameter (Db) of the active material is the accumulation of the number of particles when the particle size distribution is measured using a particle size distribution measuring apparatus based on a laser diffraction method and the particles are accumulated from small particles. This is the value of the particle diameter (D50) at which the 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 does not only evaluate primary particles of the active material, but also evaluates secondary particles formed by aggregation of the primary particles. Therefore, the number average particle diameter (Db) obtained by the particle size distribution measuring apparatus can be used as an index of the dispersion state of the active material contained in the slurry for the electricity storage device electrode. The number average particle diameter (Db) of the active material is measured by centrifuging the slurry for power storage device electrodes to precipitate the active material, then removing the supernatant, and measuring the precipitated active material by the above method. Can also be measured.

2.2. Other components The said slurry for electrical storage device electrodes can contain components other than the component mentioned above as needed. 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 active material.

2.2.2. Non-aqueous medium The slurry for an electricity storage device electrode 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 and workability when applying a slurry for an electricity storage device electrode.

2.2.3. Thickener The said slurry for electrical storage device electrodes 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 slurry for power storage device electrodes contains a thickener, the use ratio of the thickener is preferably 20% by mass or less, more preferably 0. 0% by weight based on the total solid content of the slurry for power storage device electrodes. It is 1-15 mass%, Most preferably, it is 0.5-10 mass%.

2.3. Manufacturing method of slurry for power storage device electrode The slurry for power storage device electrode according to the present embodiment is a mixture of the binder composition for power storage device, the active material, water, and an additive used as necessary. Can be manufactured. 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 slurry for an electricity storage device electrode (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 ^{3 to} 5.0 × 10 ⁵ Pa as an absolute pressure.

  As mixing and stirring for producing a slurry for an electricity storage device electrode, it is necessary to select a mixer that can stir to such an extent that no agglomerates of active material remain in the slurry and, if necessary, sufficient dispersion conditions. 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) and the number average particle diameter (Db) of the active material contained in the binder composition for an electricity storage device described above 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 active material migrates in the step of drying the formed coating film after applying the power storage device 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 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. . When such migration occurs, the distribution of the polymer particles and the active material becomes non-uniform 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 (migrate) to the gas-solid interface side of the active material layer, and the amount of polymer particles at the interface between the current collector and the active material layer is relatively small, When the penetration of the electrolyte solution into the material layer is hindered, sufficient electrical characteristics cannot be obtained, and the adhesion between the current collector and the active material layer is insufficient, resulting in peeling. Furthermore, the smoothness of the surface of the active material layer is impaired by bleeding of the polymer particles.

  However, when the ratio of the number average particle diameter of both particles (Da / Db) is in the above range, it is possible to suppress the occurrence of the problems as described above, and to achieve both the electrical characteristics and the good adhesion. The device 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 active material is small, so the area where the polymer particles and the active material are in contact with each other is small, and the powder fall resistance is not good. May be sufficient. On the other hand, if the ratio (Da / Db) exceeds the above range, the difference in the average particle size between the polymer particles and the active material becomes too large, resulting in insufficient binding force of the polymer particles, Adhesion between the active material layer may be insufficient.

  The slurry for the electricity storage device electrode 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 to 75% by mass is more preferable.

  As for the slurry for electrical storage device electrodes which concerns on this Embodiment, it is preferable that the spinnability is 30 to 80%, It is more preferable that it is 33 to 79%, It is especially preferable that it is 35 to 78%. When the spinnability is less than the above range, the leveling property may be insufficient when the slurry for an electricity storage device electrode is applied onto the current collector, and thus the electrode thickness may not be uniform. When such an electricity storage device electrode having a non-uniform thickness is used, an in-plane distribution of charge / discharge reaction occurs, making it difficult to develop stable battery performance. On the other hand, if the spinnability exceeds the above range, dripping is likely to occur when the slurry for the electricity storage device electrode is applied on the current collector, and the electricity storage device electrode having a stable quality may not be obtained. Therefore, if the spinnability is in the above range, the occurrence of these problems can be suppressed, and it becomes easy to produce an electricity storage device 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 being closed, 40 g of slurry for an electricity storage device electrode is poured into the Zahn cup. Then, when an opening part is open | released, the slurry for electrical storage device electrodes will flow out from an opening part. Here, T ₀ when opening the _opening, the T _A when the thread has finished slurry for an electricity storage device _electrode, when the when the outflow of the slurry for an electricity storage device electrodes is terminated and the T _B, hereby The “threadability” in the calligraphy can be obtained from the following mathematical formula (3).
Spinnability (%) = ((T _A −T ₀ ) / (T _B −T ₀ )) × 100 (3)

3. The electricity storage device electrode according to the present embodiment includes a current collector and a layer formed by applying and drying the above-mentioned slurry for an electricity storage device electrode on the surface of the current collector. is there. Such an electricity storage device electrode can be manufactured by applying the aforementioned slurry for an electricity storage device electrode 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 power storage device electrode thus manufactured has an active material layer containing the above-described polymer particles (A) and an active material, and optionally added optional components, on a current collector. It will be. Such an electricity storage device electrode has excellent adhesion between the current collector and the active material layer, and also has good charge / discharge rate characteristics, which is one of electrical characteristics.

  The current collector is not particularly limited as long as it is made of a conductive material. In the lithium ion secondary battery, a current collector made of metal such as iron, copper, aluminum, nickel, and stainless steel is used. Especially when aluminum is used for the positive electrode and copper is used for the negative electrode, the above-mentioned storage device is used. The effect of the slurry for an electricity storage device electrode manufactured using a binder is most apparent. 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 for applying the slurry for the electricity storage device electrode 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 amount of the electricity storage device electrode slurry applied is not particularly limited, but it is preferable that the thickness of the active material layer formed after removing the liquid medium be 0.005 to 5 mm, 0.01 to 2 mm. It is more preferable to set the amount to be.

  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 active material layer does not crack due to stress concentration or the active material layer does not peel from the current collector. be able to.

Furthermore, it is preferable to increase the density of the active material layer by pressing the dried active material layer. Examples of the pressing method include a mold press and a roll press. The density of the 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). Protective film-forming slurry The protective film-forming slurry according to the present embodiment contains the above-described binder composition for an electricity storage device (a binder composition for forming a protective film) and inorganic particles. The slurry for forming a protective film is a dispersion used for forming a protective film on the surface of the electrode or the separator or both by applying the slurry to the surface or both of the electrode and the separator and then drying the slurry.

  Along with the long life of electronic equipment in recent years, there has been a demand for longer life of power storage devices that are power sources for driving, and it is required to improve charge / discharge characteristics more than before. ing. Specifically, the following two characteristics are required. First, it is required that the internal resistance of the electricity storage device does not increase even when the electricity storage device is repeatedly charged and discharged many times. Second, it is required that the internal resistance of the electricity storage device does not increase even when the electricity storage device is overcharged. One example of an index representing such characteristics is “resistance increase rate”. An electricity storage device having a small resistance increase rate is excellent in both repeated charge / discharge resistance and overcharge resistance, and thus has excellent charge / discharge characteristics.

  Fluorine-containing organic polymers, polyamides, polyimides, and polyamideimides in the prior art have been used extensively in electricity storage devices because of their excellent oxidation resistance, but they do not satisfy the severe demands for the rate of increase in resistance in recent years. There wasn't. As a result of repeated studies in view of the above circumstances, the present inventors have formed a protective film containing polymer particles (A) containing the specific repeating unit as described above and having an endothermic peak observed in a specific range. The present inventors have found that the protective film produced from the slurry for use does not increase the internal resistance of the electricity storage device and can reduce the rate of increase in resistance.

  The polymer particles (A) contained in the protective film-forming binder composition have a repeating unit (a) of 5 to 50 parts by mass derived from the fluorine-containing compound with respect to 100 parts by mass of the polymer particles (A). And 1 to 10 parts by mass of a repeating unit (c) derived from an unsaturated carboxylic acid. Since such polymer particles (A) can firmly capture inorganic particles, both lithium ion permeability and improved toughness in the formed protective film can be achieved. As a result, the resistance increase rate can be further reduced.

  Hereinafter, each component contained in the slurry for forming a protective film according to the present embodiment will be described in detail. In addition, since it is as having mentioned above about the binder composition for electrical storage devices, description is abbreviate | omitted.

4.1. Inorganic particles The protective film-forming slurry according to the present embodiment can improve the toughness of the formed protective film by containing inorganic particles.

  As the inorganic particles, at least one kind of particles selected from the group consisting of silica, titanium oxide (titania), aluminum oxide (alumina), zirconium oxide (zirconia), and magnesium oxide (magnesia) can be used. Among these, titanium oxide and aluminum oxide are preferable from the viewpoint of further improving the toughness of the protective film. Further, as the titanium oxide, rutile type titanium oxide is more preferable.

  The number average particle diameter (Db) of the inorganic particles is preferably 1 μm or less, and more preferably in the range of 0.1 to 0.8 μm. When the number average particle diameter (Db) of the inorganic particles is within the above range, a smooth and flexible protective film can be formed, and when an electricity storage device is produced, it comes into contact with a separator or electrode disposed adjacent to the protective film. However, since the risk of damaging them is reduced, the durability of the electricity storage device is improved. In addition, it is preferable that the number average particle diameter (Db) of an inorganic particle is larger than the average hole diameter of the separator which is a porous film. Thereby, the damage to a separator can be reduced and it can prevent that an inorganic particle is clogged with the microporous of a separator.

  Here, the number average particle diameter (Db) of the inorganic particles is the accumulation of 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 frequency is 50%. Examples of such a laser diffraction particle size distribution measuring apparatus include HORIBA LA-300 series, HORIBA LA-920 series (manufactured by Horiba, Ltd.) and the like. This particle size distribution measuring apparatus is not intended to evaluate only primary particles of inorganic particles, but also targets secondary particles formed by aggregation of primary particles. Therefore, the number average particle diameter (Db) obtained by this particle size distribution measuring apparatus can be used as an indicator of the dispersion state of the inorganic particles contained in the protective film-forming slurry. The average particle diameter (Db) of the inorganic particles is measured by centrifuging the protective film-forming slurry and allowing the inorganic particles to settle, then removing the supernatant and measuring the precipitated inorganic particles by the above method. Can also be measured.

4.2. Other Components The protective film-forming slurry according to the present embodiment can contain other components such as a conductivity-imparting agent, water, a non-aqueous medium, a thickener, and a surfactant as necessary.

4.2.1. Conductivity-imparting agent As the conductivity-imparting agent, the materials and addition amounts described in the above "2.2.1. Conductivity-imparting agent" can be used as necessary.

4.2.2. Water The protective film-forming slurry according to the present embodiment can contain water. By containing water, the stability of the slurry for forming the protective film is improved, and the protective film can be produced with good reproducibility. Water has a higher evaporation rate than commonly used high-boiling solvents (for example, N-methylpyrrolidone, etc.), and is effective in improving productivity and reducing particle migration by shortening the solvent removal time. Can be expected.

  When the binder composition for an electricity storage device according to the present embodiment contains water as the liquid medium (B), the water in the protective film-forming slurry is only from the water brought in from the binder composition for an electricity storage device. Or may be the total of water brought in from the binder composition for an electricity storage device and newly added water.

4.2.3. Non-aqueous medium As the non-aqueous medium, the materials and addition amounts described in the above "2.2.2 Non-aqueous medium" can be used as necessary. Among these, when the binder composition for an electricity storage device contains water as a liquid medium, it is preferable to mix with water.

4.2.4. Thickener As the thickener, various compounds described in the above-mentioned "1.3. Other additives" can be mentioned. When the protective film-forming slurry contains a thickener, the use ratio of the thickener is preferably 20% by mass or less, more preferably 0. 0% by mass with respect to the total solid content of the slurry for the electricity storage device electrode. It is 1-15 mass%, Most preferably, it is 0.5-10 mass%.

4.2.5. Surfactant The slurry for forming a protective film according to the present embodiment can contain a surfactant from the viewpoint of improving its dispersibility and dispersion stability. Examples of the surfactant include those described in “1.1.4. Production method of polymer particles (A)”.

4.3. Method for Producing Slurry for Protective Film Formation The slurry for protective film formation according to the present embodiment is such that the binder composition for an electricity storage device described above is 0.1 to 20 mass in terms of solid content with respect to 100 parts by mass of the inorganic particles. It is preferably contained in an amount of 1 to 10 parts by mass. When the content ratio of the binder composition for an electricity storage device is 0.1 to 10 parts by mass in terms of solid content, the balance between the toughness of the protective film to be formed and the lithium ion permeability is improved. The rate of increase in resistance of the obtained electricity storage device can be further reduced.

  The slurry for forming a protective film according to this embodiment is prepared by mixing the binder composition for an electricity storage device as described above, the inorganic particles as described above, and other components used as necessary. Is done. As a means for mixing them, for example, a known mixing device such as a ball mill, a sand mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, a planetary mixer, a Hobart mixer can be used.

  For the mixing and stirring for producing the slurry for forming a protective film according to the present embodiment, a mixer capable of stirring to such an extent that the aggregate of inorganic particles does not remain in the slurry and a sufficient dispersion condition as necessary are selected. There is a need to. The degree of dispersion is preferably mixed and dispersed so that aggregates larger than at least 20 μm are eliminated. The degree of dispersion can be measured with a grain gauge.

  The slurry for forming a protective film for an electricity storage device as described above is excellent in adhesion between inorganic particles, between inorganic particles and electrodes, and between inorganic particles and separators by containing the binder composition for an electricity storage device described above. An electricity storage device electrode provided with a protective film can be formed, and an electricity storage device provided with such an electricity storage device electrode has a sufficiently low resistance increase rate.

5. Protective film The protective film according to the present embodiment can be formed by applying and drying the above-described protective film-forming slurry on the surface of the positive electrode, the negative electrode, or the separator.

  There is no particular limitation on the method for applying the protective film-forming slurry to the positive electrode, negative electrode or separator. 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 protective film forming slurry is not particularly limited, but it is preferable that the thickness of the protective film formed after removing the liquid medium is 0.5 to 4 μm, and 0.5 to 3 μm. It is more preferable to set it as an amount. When the thickness of the protective film is in the above range, the permeability of the electrolytic solution into the electrode and the liquid retaining property are improved, and an increase in the internal resistance of the electrode can be suppressed.

  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 can be appropriately set so that the liquid medium can be removed as quickly as possible within a speed range in which the protective film does not crack due to stress concentration. Specifically, the coating film is preferably dried at a temperature of 20 to 250 ° C., more preferably 50 to 150 ° C., preferably for 1 to 120 minutes, more preferably 5 to 60 minutes. be able to.

6). Electric storage device 6.1. 1st Embodiment The electrical storage device which concerns on one Embodiment of this invention is equipped with the electrical storage device electrode mentioned above, Furthermore, electrolyte solution is contained and it can manufacture 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 solution may be liquid or gel, and an electrolyte that effectively expresses the function as a battery may be selected from the known electrolytes used for the electricity storage device according to the type of the 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.

6.2. Second Embodiment In addition, an electricity storage device according to an embodiment of the present invention includes a positive electrode, a negative electrode, a protective film disposed between the positive electrode and the negative electrode, and an electrolytic solution, and the protective film Is the above-mentioned protective film. Specific examples will be described below with reference to the drawings.

6.2.1. First Specific Example FIG. 13 is a schematic diagram illustrating a cross section of an electricity storage device according to a first specific example. As shown in FIG. 13, in the electricity storage device 100, the positive electrode 30 having the positive electrode active material layer 34 formed on the surface of the positive electrode current collector 32 and the negative electrode active material layer 44 formed on the surface of the negative electrode current collector 42. A negative electrode 40, a protective film 50 provided between the positive electrode 30 and the negative electrode 40, and an electrolytic solution 60 that fills between the positive electrode 10 and the negative electrode 20 are provided. In the electricity storage device 100, no separator is provided between the positive electrode 30 and the negative electrode 40. This is because if the positive electrode 30 and the negative electrode 40 are completely fixed with a solid electrolyte or the like, the positive electrode 30 and the negative electrode 40 will not contact and short-circuit.

  The positive electrode 30 shown in FIG. 13 is formed such that the positive electrode active material layer 34 is not provided on one surface along the longitudinal direction and the positive electrode current collector 32 is exposed, but the positive electrode active material is formed on both surfaces. A layer 34 may be provided. Similarly, the negative electrode 40 shown in FIG. 13 is formed such that the negative electrode active material layer 44 is not provided on one surface along the longitudinal direction and the negative electrode current collector 42 is exposed, A negative electrode active material layer 44 may be provided.

  As the positive electrode active material and the negative electrode active material, the materials described in “2.1. Active material” can be used as necessary. As the positive electrode current collector 32 and the negative electrode current collector 42, the materials described in “3. Electric storage device electrode” can be used as necessary. The positive electrode active material layer 34 and the negative electrode active material layer 44 can be manufactured as necessary under the conditions described in “3. Power storage device electrode”.

  The protective film 50 can be formed, for example, by applying the above-described slurry for forming a protective film on the surface of the positive electrode 30 (or the negative electrode 40) and drying it. As a method for applying the protective film-forming slurry to the surface of the positive electrode 30 (or the negative electrode 40), it can be manufactured under the conditions described in the above-mentioned "5. Protective film".

  The protective film 50 is disposed between the positive electrode 30 and the negative electrode 40. In the electricity storage device 100 illustrated in FIG. 13, the protective film 50 is disposed between the positive electrode 30 and the negative electrode 40 so as to be in contact with the positive electrode active material layer 34, but is disposed so as to be in contact with the negative electrode active material layer 44. May be. The protective film 50 may be disposed as a self-supporting film between the positive electrode 30 and the negative electrode 40 without being in contact with the positive electrode 30 or the negative electrode 40. Thereby, even if it is a case where dendrites precipitate by repeating charging / discharging, since it is guarded by the protective film 50, a short circuit does not occur. Therefore, the function as an electricity storage device can be maintained.

  Although the film thickness of the protective film 50 is not specifically limited, It is preferable that it is the range of 0.5-4 micrometers, and it is more preferable that it is the range of 0.5-3 micrometers. When the thickness of the protective film 50 is within the above range, the permeability of the electrolytic solution into the electrode and the liquid retaining property are improved, and an increase in the internal resistance of the electrode can be suppressed.

  The electrolytic solution 60 is appropriately selected and used according to the type of the target power storage device. As the electrolytic solution 60, a solution in which an appropriate electrolyte is dissolved in a solvent is used.

  The type and concentration of the electrolyte in the case of manufacturing a lithium ion capacitor are the same as in the case of the lithium ion secondary battery.

6.2.2. Second Specific Example FIG. 14 is a schematic diagram illustrating a cross section of an electricity storage device according to a second specific example. As shown in FIG. 14, in the electricity storage device 200, the positive electrode 130 in which the positive electrode active material layer 134 is formed on the surface of the positive electrode current collector 132 and the negative electrode active material layer 144 in the surface of the negative electrode current collector 142 are formed. A negative electrode 140, a protective film 150 provided between the positive electrode 130 and the negative electrode 140, an electrolyte 160 filling between the positive electrode 130 and the negative electrode 140, and a separator 170 provided between the positive electrode 130 and the negative electrode 140 , With.

  The electricity storage device 200 is different from the electricity storage device 100 described above in that the protective film 150 is disposed so as to be sandwiched between the positive electrode 130 and the separator 170. In the power storage device 200 illustrated in FIG. 14, the protective film 150 is disposed so as to be sandwiched between the positive electrode 130 and the separator 170, but the protective film 150 is sandwiched between the negative electrode 140 and the separator 170. It may be arranged so that. By adopting such a configuration, even when dendrites are deposited by repeated charge and discharge, the protective film 150 guards the short circuit. Therefore, the function as an electricity storage device can be maintained.

  The protective film 150 can be formed, for example, by applying the above-described protective film-forming slurry to the surface of the positive electrode 130 (or the negative electrode 140) or the separator 170 and drying it. As a method of applying the protective film-forming slurry to the surface of the positive electrode 130 (or the negative electrode 140) or the separator 170, it can be manufactured under the conditions described in the above-mentioned “5. Protective film”.

  Any separator 170 may be used as long as it is electrically stable, chemically stable with respect to the positive electrode active material, the negative electrode active material, or the solvent, and has no electrical conductivity. . For example, a polymer nonwoven fabric, a porous film, glass or ceramic fibers in a paper shape can be used, and a plurality of these may be laminated. In particular, a porous polyolefin film is preferably used, and a composite of this with a heat-resistant material made of polyimide, glass, ceramic fibers or the like may be used.

  The other configuration of the power storage device 200 according to the second specific example is the same as that of the power storage device 100 according to the first specific example described with reference to FIG.

6.2.3. Third Specific Example FIG. 15 is a schematic diagram illustrating a cross section of an electricity storage device according to a third specific example. As illustrated in FIG. 15, in the electricity storage device 300, the positive electrode 230 in which the positive electrode active material layer 234 is formed on the surface of the positive electrode current collector 232 and the negative electrode active material layer 244 is formed on the surface of the negative electrode current collector 242. A negative electrode 240, an electrolyte solution 260 that fills between the positive electrode 230 and the negative electrode 240, a separator 270 provided between the positive electrode 230 and the negative electrode 240, and a protective film 250 formed to cover the surface of the separator 270, , With.

  The electricity storage device 300 is different from the electricity storage device 100 and the electricity storage device 200 described above in that the protective film 250 is formed so as to cover the surface of the separator 270. By adopting such a configuration, even when dendrite is deposited by repeated charge and discharge, the protective film 250 guards and no short circuit occurs. Therefore, the function as an electricity storage device can be maintained.

  The protective film 250 can be formed, for example, by applying the above-described protective film-forming slurry to the surface of the separator 270 and drying it. As a method of applying the protective film-forming slurry to the surface of the separator 270, the separator 270 can be manufactured under the conditions described in "5. Protective film".

  Regarding other configurations of the power storage device 300 according to the third specific example, the power storage device 100 according to the first specific example described with reference to FIG. 13 and the power storage according to the second specific example described with reference to FIG. Since it is the same as that of the device 200, description thereof is omitted.

6.2.4. Manufacturing Method As a manufacturing method of the electricity storage device according to the second embodiment as described above, for example, two electrodes (two of a positive electrode and a negative electrode or two of a capacitor electrode) are interposed via a separator as necessary. And a method of winding and folding the battery according to the shape of the battery, putting the battery in a battery container, injecting an electrolyte into the battery container, and sealing. 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.

6.3. Applications The power storage device as described above is suitable as a secondary battery or a capacitor mounted on an automobile such as an electric vehicle, a hybrid car, or a truck, and a secondary battery used for an AV device, an OA device, a communication device, or the like. It is also suitable as a capacitor.

7). 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. In addition, the binder composition for electrical storage devices of Examples 1-3 and Comparative Examples 1-5 is a binder composition for electrical storage devices for producing a positive electrode, and the binder composition for electrical storage devices of Examples 4, 5 is It was set as the binder composition for electrical storage devices for producing a negative electrode. The binder composition for an electricity storage device of Examples 6 to 10 and Comparative Examples 6 to 12 was a binder composition for an electricity storage device for forming a protective film.

7.1. Example 1
7.1.1. Preparation of binder composition for electricity storage device 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 were charged as an emulsifier. The temperature was raised to 60 ° C. while stirring at 350 rpm. Next, a mixed gas composed of 70% of vinylidene fluoride (VDF) as a monomer and 30% of 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 composed of 60.2% VDF 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 / HFP / GMA = 40/5/5.

  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 the inside of the separable flask was sufficiently replaced 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 the mixture was heated at 40 ° C. for 3 hours. By stirring slowly, these monomer components were absorbed by the polymer particles. 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 for an electricity storage device) 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.

7.1.2. Preparation of slurry for electricity storage device electrode First, an active material having a number average particle diameter (Db) of 0.5 μm by pulverizing commercially available lithium iron phosphate (LiFePO ₄ ) in an agate mortar and classifying with a sieve. Particles were 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 binder composition for an electricity storage device prepared above was added so that the polymer particles contained in the composition became 1 part, 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 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 electricity storage device electrode slurry.

The spinnability of the electricity storage device 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 slurry for the electricity storage device electrode 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 to the slurry for an electricity storage device electrode can not flow out. The measured values T ₀ , T _A and T _B were substituted into the following formula (3) to obtain the spinnability.
Spinnability (%) = ((T _A −T ₀ ) / (T _B −T ₀ )) × 100 (3)

  It can be judged that the spinnability in the electricity storage device electrode slurry is good when it is 30 to 80%.

7.1.3. Production and evaluation of electricity storage device electrode and electricity storage device 7.1.3.1. Production of electricity storage device electrode (positive electrode) The slurry for electricity storage device electrode prepared above is uniformly applied to the surface of a current collector made of aluminum foil having a thickness of 30 μm by a doctor blade method so that the film thickness after drying becomes 100 μm. It was applied and dried at 120 ° C. for 20 minutes. Then, the electrical storage device 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.

7.1.3.2. Evaluation of power storage device electrodes (crack rate)
The produced electricity storage device electrode was cut into an electrode plate having a width of 2 cm and a length of 10 cm, and the electrode plate was repeatedly bent at 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 (4).
Crack rate (%) = {length with crack (mm) ÷ total length of electrode plate (mm)} × 100 (4)

  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.

7.1.3.3. 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) (solid content conversion), graphite as negative electrode active material (Product made by Showa Denko KK, product name “SCMG”, number average particle size = 22 μm) 100 parts (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 >.

7.1.3.4. Assembly of lithium ion battery cell In a glove box substituted with Ar so that the dew point is −80 ° C. or lower, the counter electrode (negative electrode) produced above is punched and molded to a diameter of 15.95 mm. It was mounted on a product name “HS flat cell” manufactured by Izumi Co., Ltd.). 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, A lithium ion battery cell (power storage device) was assembled by placing the positive electrode manufactured in the above-described method by punching and molding the positive electrode to a diameter of 16.16 mm, and sealing the outer body of the bipolar coin cell with a screw. 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).

7.1.3.5. Evaluation of electricity storage devices (evaluation of discharge rate characteristics)
About the electrical storage device manufactured above, charging is started at a constant current (0.2 C), and when the voltage reaches 4.2 V, charging is continued at a constant voltage (4.2 V). The charge capacity at 0.2 C was measured with the time when the temperature reached 0.01 C being completed (cut-off). 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.

7.2. Example 2 and Comparative Example 3
7.2.1. Preparation of Binder Composition for Electricity Storage Device Example 1 except that the composition of the monomer and the amount of the emulsifier were appropriately changed in “7.1.1. Preparation of Binder Composition for Electricity Storage Device” in Example 1 above. Similarly, 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, so that the solid content concentration is 40%. An aqueous dispersion was obtained. 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.

7.2.2. Preparation of slurry for electricity storage device electrode First, in “7.1.2. Preparation of slurry for electricity storage device electrode” in Example 1, the number average particle diameter (Db ) Active material particles (LiFePO ₄ ) of 10 μm, 7 μm, 3 μm, and 1 μm were prepared. The active material particles thus obtained were used in the following examples and comparative examples. In Example 2, 10 μm and Comparative Example 3 used 7 μm active material particles, respectively, except that the types and amounts of thickeners listed in Table 1 were used. In the same manner as in “Preparation of slurry for electricity storage device electrode”, a slurry for electrode (positive electrode) was prepared, and its spinnability was measured. The value of the spinnability is also shown in Table 1.

7.2.3. Production and evaluation of electricity storage device electrode and electricity storage device An electricity storage device electrode (positive electrode) and an electricity 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.

7.3. Example 3
7.3.1. Preparation of Binder Composition for Electricity Storage Device Example 1 except that the composition of the monomer gas and the amount of emulsifier were changed appropriately in “7.1.1. Preparation of Binder Composition for Electricity Storage Device” in Example 1 above. In the same manner as described above, an aqueous dispersion containing polymer particles having the composition shown in Table 1 was prepared, and water was removed under reduced pressure or added in accordance with the solid content concentration of the aqueous dispersion to obtain a solid content concentration of 40%. An aqueous 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 for an electricity storage device using NMP as a liquid 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.

7.3.2. Preparation of slurry for power storage device electrode In Example 3, active material particles (LiFePO ₄ ) having a number average particle diameter (Db) of 3 μm obtained above were used.

  Next, 3 parts thickener (trade name “CMC2200”, manufactured by Daicel Chemical Industries, Ltd.) in a biaxial planetary mixer (trade name “TK Hibismix 2P-03” manufactured by PRIMIX Co., Ltd.) (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 for an electricity storage device prepared above (in terms of solid content) and 68 parts of NMP were added, and 2 hours at 60 rpm. The paste was obtained by stirring. 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 at 1800 rpm for 1.5 minutes under vacuum for 5 minutes to prepare an electricity storage device electrode slurry.

7.3.3. Production and Evaluation of Electricity Storage Device Electrode and Electricity Storage Device Electricity storage was carried out in the same manner as in “7.1.3. Production and Evaluation of Electricity Storage Device Electrode and Electricity Storage Device” in Example 1, except that the above slurry for electricity storage device electrode was used. A device electrode (positive electrode) and a power storage device were manufactured and evaluated. The evaluation results are also shown in Table 1.

7.4. Comparative Example 1
7.4.1. Preparation of Binder Composition for Electricity Storage Device After the inside of a 7 L capacity separable flask was sufficiently purged with nitrogen, an emulsifier “ADEKA rear soap SR1025” (trade name, manufactured by ADEKA Corporation) 0.5 part, styrene (ST) 25 Of water, 5 parts of butadiene (BD) and 130 parts of water were added sequentially, and then 20 mL of a tetrahydrofuran solution containing 0.5 part of azobisisobutyronitrile as an oil-soluble polymerization initiator was added, and the temperature was raised to 75 ° C. The reaction was carried out for 3 hours and further at 85 ° C. for 2 hours. After adding 20 parts of glycidyl methacrylate (GMA) 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, 50 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), 15 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.

7.4.2. Preparation of slurry for electricity storage device electrode Lithium iron phosphate (LiFePO ₄ ) having a number average particle diameter (Db) of 7 μm obtained above was used as active material particles, and the types and amounts of thickening described in Table 1 were used. Except for using the agent, an electrode (positive electrode) slurry was prepared in the same manner as in “7.1.2. Preparation of electricity storage device electrode slurry” in Example 1, and the spinnability was measured. The value of the spinnability is also shown in Table 1.

7.4.3. Production and evaluation of electricity storage device electrode and electricity storage device An electricity storage device electrode (positive electrode) and an electricity 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.

7.5. Comparative Examples 2, 4, 5
7.5.1. Preparation of Binder Composition for Electricity Storage Device Comparative Example 1 except that the composition of the monomer and the amount of emulsifier were appropriately changed in “7.4.1. Preparation of Binder Composition for Electricity Storage Device” in Comparative Example 1 above. Similarly, 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, so that the solid content concentration is 40%. An aqueous dispersion was obtained. 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.

7.5.2. Preparation of slurry for electricity storage device electrode In Comparative Example 2, the number average particle diameter (Db) obtained above is 1 μm, and in Comparative Examples 4 and 5, the iron phosphate whose number average particle diameter (Db) is 7 μm is obtained. “7.1.2. Preparation of slurry for electricity storage device electrode in Example 1 except that lithium (LiFePO ₄ ) was used as the active material particles and the thickeners of the type and amount described in Table 1 were used. In the same manner as above, a slurry for an electricity storage device electrode (positive electrode) was prepared and its spinnability was measured. The value of the spinnability is also shown in Table 1.

7.5.3. Production and evaluation of electricity storage device electrode and electricity storage device An electricity storage device electrode (positive electrode) and an electricity 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.

7.6. Example 4
7.6.1. Preparation of Binder Composition for Electricity Storage Device Example 1 except that the composition of the monomer and the amount of the emulsifier were appropriately changed in “7.1.1. Preparation of Binder Composition for Electricity Storage Device” in Example 1 above. Similarly, 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, so that the solid content concentration is 40%. An aqueous dispersion was obtained. 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.

7.6.2. Preparation of slurry for electricity storage device electrode Next, a thickener (trade name “CMC1150”, manufactured by Daicel Chemical Industries, Ltd.) was added to a biaxial planetary mixer (product name “TK Hibismix 2P-03” manufactured by PRIMIX Corporation). 7 parts (in terms of solid content), 100 parts of graphite (made by Kanto Chemical Co., Ltd., product name “graphite powder” ground to D50 = 10 μm) as negative electrode active material (in terms of solid content), and 68 parts of water were added. Stirring was performed at 60 rpm for 1 hour. Thereafter, 2 parts of the binder composition for an electricity storage device prepared above (in terms of solid content) 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 at 1800 rpm for 1.5 minutes under vacuum for 5 minutes to prepare an electricity storage device electrode slurry. The spinnability of the negative electrode slurry was measured by the method described in “7.1.2. Preparation of electricity storage device electrode slurry” in Example 1. The results are also shown in Table 1.

7.6.3. Production and evaluation of electricity storage device electrode and electricity storage device 7.6.3.1. Manufacture of electricity storage device electrode (negative electrode) Doctor blade method so that the film thickness after drying the slurry for electricity storage device electrode (negative electrode) prepared above is 150 μm on the surface of a current collector made of copper foil having a thickness of 20 μm Was applied uniformly and dried at 120 ° C. for 20 minutes. Then, the electrical storage device 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 >.

7.6.3.2. Evaluation of Crack Rate of Negative Electrode The crack rate of the negative electrode was measured in the same manner as in “7.1.3.2. Electrode Evaluation (Crack Rate)” in Example 1. The results are also shown in Table 1.

7.6.3.3. 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 >.

7.6.3.4. Assembly of Lithium Ion Battery Cell A lithium ion battery cell was assembled in the same manner as in “7.1.3.4. Assembly of lithium ion battery cell” in Example 1.

7.6.3.5. Evaluation of electricity storage devices (evaluation of discharge rate characteristics)
The electricity storage device was evaluated in the same manner as in “7.1.3.5. Evaluation of electricity storage device (evaluation of discharge rate characteristics)” in Example 1. The results are also shown in Table 1.

7.7. Example 5
7.7.1. Preparation of Binder Composition for Electricity Storage Device In “7.6.1. Preparation of Binder Composition for Electricity Storage Device” in Example 4 above, the composition of the monomer and the amount of the emulsifier were changed as appropriate, and graphite was used. 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 product name “SCMG” (Db = 22 μm) manufactured by Co., Ltd. was used. By removing or adding water under reduced pressure according to the solid content concentration, an aqueous dispersion having a solid content concentration of 40% was obtained. 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.

7.7.2. Preparation of slurry for electricity storage device electrode (negative electrode) Except for using the types and amounts of thickeners listed in Table 1, “7.6.2. Preparation of slurry for electricity storage device electrode (negative electrode)” in Example 4 In the same manner as above, a slurry for an electricity storage device electrode (negative electrode) was prepared, and its spinnability was measured. The results are also shown in Table 1.

7.7.3. Production and Evaluation of Electricity Storage Device Electrode (Negative Electrode) and Electricity Storage Device An electricity storage device electrode (negative electrode) and an electricity 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: Vinylidene fluoride ・ HFP: Propylene hexafluoride ・ TFE: Tetrafluoroethylene <Monofunctional (meth) acrylic acid ester>
MMA: methyl methacrylate EHA: 2-ethylhexyl acrylate <polyfunctional (meth) acrylate>
AMA: allyl methacrylate GMA: glycidyl methacrylate HEMA: hydroxyethyl methacrylate <unsaturated carboxylic acid>
AA: acrylic acid MAA: methacrylic acid <other monomer>
・ AN: Acrylonitrile ・ ST: Styrene ・ BD: Butadiene <Active material>
LFP: lithium iron phosphate (LiFePO ₄ )
・ GF: Graphite

  In addition, CMC1120, CMC1150, CMC2200, CMC2280, and CMC2450 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.

7.8. Example 6
7.8.1. Preparation of slurry for forming protective film Titanium oxide (product name “KR380”, manufactured by Titanium Industry Co., Ltd., rutile type, average number particle diameter 0.38 μm) as inorganic particles is 20 parts by mass with respect to 100 parts by mass of water. 5 parts by mass of the binder composition for an electricity storage device prepared in “7.1.1. Preparation of binder composition for an electricity storage device” in Example 1 in terms of solid content with respect to inorganic particles, a thickener (Daicel Chemical Co., Ltd.) Product, product name “CMC1120”) 1 part by mass, K. Mixing and dispersing treatment was performed using a film mix (R) 56-50 type (manufactured by PRIMIX Co., Ltd.) to prepare a protective film-forming slurry in which titanium oxide was dispersed.

7.8.2. Production and Evaluation of Electricity Storage Device Electrode and Electricity Storage Device After applying the protective film-forming slurry obtained above to the surface of the positive electrode active material layer of the positive electrode produced in Example 1 above using a die coating method, A protective film was formed on the surface of the positive electrode active material layer by drying for 5 minutes. The protective film had a thickness of 3 μm.

  A lithium ion battery cell was produced in the same manner as in Example 1 except that a positive electrode having a protective film formed on the surface of the positive electrode active material layer was used. However, when the positive electrode was mounted on the separator, the positive electrode was formed so that the surface on which the protective film of the positive electrode was formed and the separator faced each other.

7.8.3. Measurement of remaining capacity rate and rate of increase in resistance When the lithium ion battery cell produced above was placed in a constant temperature bath at 25 ° C., charging was started at a constant current (0.2 C), and when the voltage reached 4.1 V. Charging was continued at a constant voltage (4.1 V), and when the current value reached 0.01 C, charging was completed (cut off). Next, discharging was started at a constant current (0.2 C), and the time when the voltage reached 2.5 V was regarded as discharging completion (cut-off) (aging charge / discharge).

  The cell after the aging charge / discharge is put in a thermostat at 25 ° C., and charging is started at a constant current (0.2 C). When the voltage reaches 4.1 V, the cell is continuously maintained at a constant voltage (4.1 V). Charging was continued, and charging was completed (cut off) when the current value reached 0.01C. Next, discharge was started at a constant current (0.2 C), and when the voltage reached 2.5 V, the discharge was completed (cut off), and C1 which was the value of the discharge capacity (initial) at 0.2 C was measured. did.

  The cell after the discharge capacity (initial) measurement was placed in a constant temperature bath at 25 ° C., charging was started at a constant current (0.2 C), and when the voltage reached 4.1 V, the constant voltage (4.1 V continued The charging was continued at), and the time when the current value reached 0.01 C was defined as the completion of charging (cut-off).

  An EIS measurement ("Electrochemical Impedance Spectroscopy", "electrochemical impedance measurement") was performed on the charged cell, and an initial resistance value EISA was measured.

  Next, the cell in which the initial resistance value EISa was measured was placed in a constant temperature bath at 60 ° C., and charging was started at a constant current (0.2 C). When the voltage reached 4.4 V, the constant voltage (4 4V), charging was continued for 168 hours (overcharge acceleration test).

  After that, the charged cell was placed in a constant temperature bath at 25 ° C., the cell temperature was lowered to 25 ° C., and then discharging was started at a constant current (0.2 C), and the voltage became 2.5V Was completed (cutoff), and C2 as a value of the discharge capacity at 0.2 C (after the test) was measured.

  The cell having the above discharge capacity (after the test) is placed in a constant temperature bath at 25 ° C., and charging is started at a constant current (0.2 C). The charging was continued at, and the time when the current value reached 0.01 C was regarded as charging completion (cut-off). Next, discharging was started at a constant current (0.2 C), and the time when the voltage reached 2.5 V was regarded as completion of discharging (cut-off). EIS measurement of this cell was performed, and EISb which is a resistance value after application of thermal stress and overcharge stress was measured.

The residual capacity ratio obtained by substituting the above measured values into the following formula (5) is 80.5%, and the resistance increase rate obtained by substituting the above measured values into the following formula (6) is 210. %Met.
Remaining capacity ratio (%) = (C2 / C1) × 100 (5)
Resistance increase rate (%) = (EISb / EISa) × 100 (6)

  When this remaining capacity ratio is 75% or more and the resistance increase rate is 300% or less, it can be evaluated that the durability is good.

7.9. Examples 7 to 10, Comparative Example 6 to Comparative Example 10
An electricity storage device was produced and evaluated in the same manner as in Example 6 except that the binder composition for an electricity storage device used in Examples 2 to 5 and Comparative Examples 1 to 5 was used. The evaluation results are also shown in Table 2. In addition, the binder composition for electrical storage devices of Examples 7-10 respond | corresponds to the binder composition for electrical storage devices of Examples 2-5, respectively, The binder composition for electrical storage devices of Comparative Examples 6-10 is respectively Although it respond | corresponds to the binder composition for electrical storage devices of Comparative Examples 1-5, in Examples 7-10 and Comparative Example 10, the kind of liquid medium was changed into the thing of Table 2, respectively.

7.10. Comparative Example 11
7.11. Synthesis of polyimide Polyimide was synthesized by the method described in JP-A-2009-87562. That is, in a four-necked flask equipped with a condenser and a nitrogen gas inlet, 1.0 mol of 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride and o-tolidine diisocyanate 0 were added. .95 mol is mixed with N-methyl-2-pyrrolidone (NMP) so that the solid content concentration is 20% by mass, and 0.01 mol of diazabicycloundecene is added as a catalyst and stirred. Reacted for hours.

7.10.2. Preparation of slurry for forming protective film and production of electricity storage device In “7.8.1. Preparation of slurry for forming protective film” in Example 6 above, the polyimide NMP solution obtained above was used as a binder solution. A slurry for forming a protective film was prepared in the same manner as in Example 6 except that NMP was used instead of water, and a positive electrode and an electricity storage device on which a protective film using polyimide as a binder was formed were manufactured and evaluated. The evaluation results are also shown in Table 2.

7.11. Comparative Example 12
7.11.1. Synthesis of polyamideimide Polyamideimide was synthesized by the method described in JP-A-2007-154029. That is, 0.7 mol of trimellitic anhydride (TMA), 3,3 ′, 4,4′-benzophenone tetracarboxylic anhydride (BTDA) 0. 3 mol, 1 mol of naphthalene diisocyanate (NDI) and 0.01 mol of diazabicycloundecene (DBU) were charged together with N-methyl-2-pyrrolidone (NMP) to a solid content concentration of 15% at 80 ° C. The reaction was performed for about 3 hours.

7.11.2. Preparation of slurry for forming protective film and production of electricity storage device In “7.8.1. Preparation of slurry for forming protective film” in Example 6 above, the NMP solution of polyamideimide obtained above was used as a binder solution, and A slurry for forming a protective film was prepared in the same manner as in Example 6 except that NMP was used instead of water, and a positive electrode and an electricity storage device on which a protective film using polyamideimide as a binder was formed were manufactured and evaluated. The evaluation results are also shown in Table 2.

In addition, the abbreviation of each component in Table 2 is the same as that in Table 1 except for the inorganic particles. The inorganic particles used are shown below.
<Inorganic particles>
-Titanium oxide: The product name “KR380” (manufactured by Titanium Industry Co., Ltd., rutile type, number average particle size 0.38 μm) is used as it is, or the product name “KR380” is ground in an mortar and sieved. Thus, titanium oxide having a number average particle size of 0.08 μm and 0.12 μm was prepared and used.
Aluminum oxide: Product name “AKP-3000” (manufactured by Sumitomo Chemical Co., Ltd., number average particle size 0.74 μm), or product name “AKP-50” (manufactured by Sumitomo Chemical Co., Ltd., number average particle size 0.22 μm) Was used.
・ Zirconium oxide: Product name “UEP zirconium oxide” (manufactured by Daiichi Elemental Chemical Co., Ltd., number average particle diameter 0.67 μm)
Silica: Product name “Seahoster (R) KE-S50” (manufactured by Nippon Shokubai Co., Ltd., number average particle size 0.54 μm), or product name “Seahoster (R) KE-S100” (manufactured by Nippon Shokubai Co., Ltd., number An average particle size of 0.98 μm) was used.
Magnesium oxide: Product name “PUREMAG® FNM-G” (manufactured by Tateho Chemical Co., Ltd., number average particle size 0.50 μm)

7.12. Evaluation Results As is apparent from Table 1 above, according to the slurry for an electricity storage device electrode prepared using the binder composition for an electricity storage device according to the present invention shown in Examples 1 to 5, the current collector and the active material An electric storage device electrode having good binding property with the layer, low crack rate, and excellent adhesion was obtained. Moreover, the electrical storage device (lithium ion secondary battery) provided with these electrical storage device electrodes had favorable discharge rate characteristics.

  As apparent from Table 2 above, the electricity storage device (lithium ion secondary battery) comprising the electricity storage device electrode having the protective film according to the present invention shown in Examples 6 to 10 is the residual after the initial resistance and durability test. It was excellent in capacity and suppression of resistance rise. On the other hand, in Comparative Examples 6-10, the electrical storage device which satisfy | fills both favorable residual capacity | capacitance and suppression of a resistance increase rate was not obtained. When the binders of Comparative Examples 11 to 12 were used, the initial resistance of the electricity storage device was high, and the resistance increase rate of the electricity storage device after the durability test was poor.

  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 24, 24a, 24b, 24c, 24d, 24e, 24f ... second polymer particles, 100,200,300 ... electric storage device, 30,130,230 ... positive electrode, 32,132 , 232 ... Positive electrode current collector, 34, 134, 234 ... Positive electrode active material layer, 40, 140, 240 ... Negative electrode, 42, 142, 242 ... Negative electrode current collector, 44, 144, 244 ... Negative electrode active material layer, 50 , 150, 250 ... protective film, 60, 160, 260 ... electrolyte, 170, 270 ... separator

Claims (17)

Unsaturated carboxylic acid and monofunctional (meth) acrylic acid ester in the presence of polymer particles containing repeating unit (a) derived from fluorine-containing compound and repeating unit (b) derived from polyfunctional (meth) acrylic acid ester Polymer particles (A) further comprising a repeating unit (c) derived from an unsaturated carboxylic acid and a repeating unit (d) derived from a monofunctional (meth) acrylic acid ester, and a liquid medium (B) In a binder composition for an electricity storage device containing,
When differential scanning calorimetry (DSC) was performed on the polymer particles (A) in accordance with JIS K7121, one endothermic peak in the temperature range of −30 ° C. to 30 ° C. and a temperature of 80 ° C. to 150 ° C. A binder composition for an electricity storage device, wherein one endothermic peak in the range is observed. The polymer particles (A) are first polymer particles containing a repeating unit (a) derived from the fluorine-containing compound and a repeating unit (b) derived from the polyfunctional (meth) acrylic ester, The second polymer particle containing a repeating unit (c) derived from an unsaturated carboxylic acid and a repeating unit (d) derived from the monofunctional (meth) acrylic ester has a structure in close contact with each other. 2. The binder composition for an electricity storage device according to 1. The polymer particles in (A), the repeating unit (a) between the amount ratio by mass of the repeating unit (b) 2: 1~10: in 1, and claim 1 or claim 2 2. The binder composition for an electricity storage device according to 1. Number average particle size of the polymer particles (A) is in the range of 50 to 400 nm, according to claim 1 to an electricity storage device for the binder composition according to any one of claims 3. Wherein the ratio of the major axis and (Rmax) and minor axis (Rmin) of the polymer particles (A) (Rmax / Rmin) is in the range of 1.1 to 1.5, any of claims 1 to 4 one The binder composition for an electricity storage device according to item. 5 to 50 parts by mass of the repeating unit (a) derived from the fluorine-containing compound and 1 to 10 parts by mass of the repeating unit (c) derived from the unsaturated carboxylic acid with respect to 100 parts by mass of the polymer particles (A). The binder composition for electrical storage devices as described in any one of Claims 1 thru | or 5 containing a part. The binder composition for an electricity storage device according to any one of claims 1 to 6 , which is used for producing a positive electrode of the electricity storage device. The slurry for electrical storage device electrodes containing the binder composition for electrical storage devices as described in any one of Claims 1 thru | or 7 , and an active material. An electricity storage device electrode comprising: a current collector; and an active material layer produced by applying and drying the electricity storage device electrode slurry according to claim 8 on a surface of the current collector. The slurry for protective film formation containing the binder composition for electrical storage devices as described in any one of Claims 1 thru | or 6 , and an inorganic particle. 11. The slurry for forming a protective film according to claim 10 , wherein the inorganic particles are at least one particle selected from the group consisting of silica, titanium oxide, aluminum oxide, zirconium oxide, and magnesium oxide. The protective film produced using the slurry for protective film formation of Claim 10 or Claim 11 . An electricity storage device comprising the electricity storage device electrode according to claim 9 . An electricity storage device comprising the protective film according to claim 12 . A positive electrode and a negative electrode;
The electricity storage device according to claim 14 , wherein the protective film is in contact with at least one surface of the positive electrode and the negative electrode. The electricity storage device according to claim 15 , further comprising a separator disposed between the positive electrode and the negative electrode. The electricity storage device according to claim 14 , further comprising a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, wherein a surface of the separator is covered with the protective film.

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