JP2017212090A - Binder composition for power storage device, slurry for power storage device, separator for power storage device, power storage device electrode, and power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a binder composition for a power storage device electrode, providing a power storage device high in adhesion and safety and excellent in charge/discharge characteristics.SOLUTION: A binder composition for a power storage device electrode according to the present invention contains a polymer (A) having a polymerization average molecular weight (Mw) of 10,000 or more and a resin (B) containing repeating units with an alicyclic hydrocarbon group and having a polymerization average molecular weight (Mw) of less than 10,000.SELECTED DRAWING: None

Description

  The present invention relates to an electrical storage device binder composition, an electrical storage device slurry, an electrical storage device separator, an electrical storage device electrode, and an electrical storage device.

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

  The electricity storage device having such a high voltage and high energy density is required to be further downsized. In order to achieve miniaturization of an electricity storage device, it is essential not only to reduce the thickness of power generation elements such as a positive electrode and a negative electrode, but also to reduce the thickness of a separator or the like that separates the positive electrode and the negative electrode. However, when the interval between the positive electrode and the negative electrode is reduced due to the miniaturization of the electricity storage device, there may be a problem that a short circuit is likely to occur.

  In the event of an abnormality such as a short circuit or overcharge, there is a greater risk of excessive heat generation than before due to the high voltage and high energy density of the electricity storage device. For this reason, the electric storage device is provided with several means for ensuring safety even in the event of an abnormality, and one of them is a separator shutdown function. The shutdown function is a function that suppresses excessive heat generation by stopping the battery reaction by blocking the movement of ions when the temperature of the battery rises for some reason and blocking the movement of ions. In particular, one of the reasons why polyethylene porous membranes are frequently used as power storage device separators using metal ions such as lithium ions is that they have an excellent shutdown function. However, as the electricity storage device increases in voltage and energy density, the amount of heat generated during abnormal heat generation increases rapidly, and when the temperature suddenly reaches high temperatures or when heat is required after shutdown and the high temperature state is maintained for a long time. There is. In such a case, there is a risk that the separator contracts or breaks and short-circuits between the positive and negative electrodes, causing further heat generation.

  In order to avoid such a phenomenon, for example, in Patent Document 1 and Patent Document 2, a technique for improving battery characteristics by melting and kneading a polymer and inorganic particles to form a microporous film on a porous separator substrate. Is being considered. On the other hand, Patent Document 3 discusses a technique for improving battery characteristics by forming a porous protective film on at least one surface of a positive electrode and a negative electrode. Moreover, in patent document 4, the technique which improves a battery characteristic is laminated | stacked by laminating | stacking the porous film containing a polymer and nonelectroconductive particle on an organic separator base material.

  Recently, from the viewpoint of achieving the demand for higher output and higher energy density of power storage devices, studies are being made on the use of materials with large lithium storage capacity. For example, an approach to improve the lithium occlusion amount by using graphite having higher crystallinity as an active material and to realize a capacity close to the theoretical occlusion amount (about 370 mAh / g) of the carbon material is being advanced. . On the other hand, Patent Document 5 discloses an approach in which a silicon material having a maximum lithium occlusion amount of about 4200 mAh / g is used as an active material. In any case, it is considered that the capacity of the electricity storage device is greatly improved by utilizing such an active material having a large lithium storage amount.

  However, an active material using such a material having a large amount of lithium storage is accompanied by a large volume change due to the storage and release of lithium. For this reason, when the conventionally used binder for electrodes is applied to such a material having a large lithium storage amount, the adhesive cannot be maintained, and the active material is peeled off. Capacity drop occurs.

International Publication No. 2006/0253323 JP 2008-214425 A JP 2009-54455 A International Publication No. 2010/074202 JP 2004-185810 A

According to the prior art using inorganic particles as described in the above-mentioned Patent Documents 1 to 4, a short circuit caused by dendrite generated along with charging / discharging by forming a protective film on the separator or electrode surface. Although it can be suppressed, when the separator hole closes due to abnormal heat generation and the shutdown function is manifested, the separator causes thermal contraction, and the positive and negative electrodes are short-circuited at the contracted part, and the shutdown function is not sufficiently manifested There was sex.

  Therefore, some embodiments according to the present invention provide a composition for an electricity storage device for forming a protective film on the surface of a separator or an electrode, which can suppress the thermal contraction of the separator and suppress an increase in internal resistance of the electricity storage device, and A slurry for an electricity storage device containing the composition is provided.

  On the other hand, the electrode binder described in the above-mentioned Patent Document 5 does not have sufficient adhesion to put an active material using a material having a large amount of lithium occlusion into practical use, and the electrode characteristics are improved by repeated charge and discharge. Due to the deterioration, there is a problem that the durability required for practical use cannot be obtained sufficiently.

  Accordingly, some embodiments according to the present invention provide a binder composition for an electricity storage device for producing an electricity storage device electrode having excellent adhesion and charge / discharge characteristics, and a slurry for an electricity storage device containing the composition. It is.

  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:
A polymer (A) having a polymerization average molecular weight (Mw) of 10,000 or more;
A resin (B) containing a repeating unit having an alicyclic hydrocarbon group and having a polymerization average molecular weight (Mw) of less than 10,000;
It is characterized by containing.

[Application Example 2]
In the binder composition for an electricity storage device of Application Example 1,
When the content of the polymer (A) is Ma parts by mass and the content of the resin (B) is Mb parts by mass, the value of Mb / Ma can be in the range of 0.1-20.

[Application Example 3]
In the binder composition for an electricity storage device of Application Example 1 or Application Example 2,
The polymer (A) can contain a repeating unit derived from an unsaturated carboxylic acid ester and a repeating unit derived from an unsaturated carboxylic acid.

[Application Example 4]
In the binder composition for an electricity storage device of Application Example 3,
The polymer (A) can further contain a repeating unit derived from a conjugated diene compound and a repeating unit derived from an aromatic vinyl compound.

[Application Example 5]
In the binder composition for an electricity storage device of Application Example 3 or Application Example 4,
When the repeating unit derived from the unsaturated carboxylic acid ester includes a repeating unit having an alicyclic hydrocarbon group, and the total repeating unit of the polymer (A) is 100% by mass, the alicyclic hydrocarbon group The repeating unit having can be 0.1 to 20% by mass.

[Application Example 6]
In the binder composition for an electricity storage device according to any one of Application Examples 1 to 5,
The polymer (A) may be a fluorine-containing polymer containing a repeating unit derived from a fluorine-containing ethylene monomer.

[Application Example 7]
In the binder composition for an electricity storage device according to any one of Application Examples 1 to 6,
The said resin (B) can be 50 mass% or more of the repeating unit which has an alicyclic hydrocarbon group.

[Application Example 8]
One aspect of the slurry for an electricity storage device 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 7, and an active material, It is characterized by the above-mentioned.

[Application Example 9]
One aspect of the electrode for an electricity storage device according to the present invention is:
It is characterized by comprising a current collector and a layer formed by applying and drying the power storage device slurry of Application Example 8 on the surface of the current collector.

[Application Example 10]
One aspect of the slurry for an electricity storage device 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 7, and a filler.

[Application Example 11]
One aspect of the separator for an electricity storage device according to the present invention is:
A layer formed by applying and drying the slurry for an electricity storage device of Application Example 10 is provided on the surface.

[Application Example 12]
One aspect of the electricity storage device according to the present invention is:
It has at least one of the electrode for electrical storage devices of the application example 9, and the separator for electrical storage devices of the application example 11.

  The composition for an electricity storage device according to the present invention can also be used as a material for forming a protective film for suppressing a short circuit caused by dendrites generated during charging and discharging, and the binding ability between active materials. In addition, it can be used as a material for producing an electricity storage device electrode with improved adhesion between the active material and the current collector. By forming a protective film on the surface of the separator or electrode using the composition for an electricity storage device according to the present invention, the thermal contraction of the separator is effectively suppressed, and the electrolyte has excellent permeability and liquid retention, An increase in resistance can be suppressed. Thereby, since the degree to which the internal resistance of the electricity storage device increases due to repeated charge / discharge or overcharge is reduced, an electricity storage device having excellent charge / discharge characteristics can be obtained.

  Moreover, the electrical storage device electrode which is excellent in adhesiveness and charging / discharging characteristic can be produced by forming an active material layer using the composition for electrical storage devices according to the present invention.

It is the schematic diagram which showed the cross section of the electrical storage device which concerns on 1st Embodiment. It is the schematic diagram which showed the cross section of the electrical storage device which concerns on 2nd Embodiment. It is the schematic diagram which showed the cross section of the electrical storage device which concerns on 3rd Embodiment.

  Hereinafter, preferred embodiments according to the present invention will be described in detail. It should be understood that the present invention is not limited to only the embodiments described below, and includes various modifications that are implemented without departing from the scope of the present invention. In this 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 this embodiment comprises a polymer (A) having a polymerization average molecular weight (Mw) of 10,000 or more (hereinafter also referred to as “polymer (A)”), and an alicyclic ring. And a resin (B) (hereinafter, also referred to as “resin (B)”) having a repeating unit having a formula hydrocarbon group of 50% by mass or more and a polymerization average molecular weight (Mw) of less than 10,000. . The binder composition for an electricity storage device according to the present embodiment can be used as a material for forming a protective film for suppressing a short circuit caused by dendrite that occurs with charge and discharge, and between active materials. It can also be used as a material for producing an electricity storage device electrode (active material layer) with improved binding ability, ability to adhere an active material to a current collector, and powder fall resistance. Hereafter, each component contained in the binder composition for electrical storage devices which concerns on this embodiment is demonstrated in detail.

1.1. Polymer (A) having a polymerization average molecular weight (Mw) of 10,000 or more
The binder composition for an electricity storage device according to this embodiment contains a polymer (A) having a polymerization average molecular weight (Mw) of 10,000 or more. The polymer (A) may be in the form of a latex in which it is dissolved or dispersed in a liquid medium, but is preferably in the form of a latex in which the particles of the polymer (A) are dispersed in the liquid medium. It is preferable that the binder composition for an electricity storage device according to the present embodiment is in a latex form because not only the stability of the slurry for an electricity storage device prepared by mixing with an active material is good, but also the coating property is good. .

  The polymer (A) is not particularly limited, but specifically, at least one selected from the group consisting of an acrylic polymer, a conjugated diene polymer, a fluorine-containing polymer, a polyamic acid, and an imidized polymer thereof. Examples include seeds. Among these, acrylic polymers, conjugated diene polymers, and fluorine-containing polymers are preferable. The polymers exemplified above may be used alone or in combination of two or more.

  The polymer (A) may be prepared by appropriately adjusting the monomer polymerization method.

1.1.1.1. Repeating unit (a1) having an alicyclic hydrocarbon group
The polymer (A) may contain a repeating unit (a1) having an alicyclic hydrocarbon group. When the repeating unit (a1) having an alicyclic hydrocarbon group is used, it is preferable because it has high hydrophobicity, and adhesion with a highly hydrophobic separator or electrode is improved.
Although it does not specifically limit as repeating unit (a1) which has an alicyclic hydrocarbon group, Specifically, the cycloalkyl ester of (meth) acrylic acid etc. are mentioned. Examples of the cycloalkyl ester of (meth) acrylic acid include cyclohexyl (meth) acrylate.

In the polymer (A), when the repeating unit (a1) is included, the content ratio is preferably 0.1 to 99 parts by mass when the total of all repeating units is 100 parts by mass. More preferably, it is 20 parts by mass. When the content ratio of the repeating unit (a1) in the polymer (A) is in the above range, the binding property can be further improved.
1.1.1.2. Repeating unit having a nitrile group (a2)
The polymer (A) may contain a repeating unit (a2) having a nitrile group. When the repeating unit (a2) having a nitrile group is used, it is preferable because it has high hydrophobicity, and adhesion with a highly hydrophobic separator or electrode is improved.
The repeating unit (a2) having a nitrile group is not particularly limited, and specific examples include α, β-unsaturated nitrile compounds.

  Specific examples of the α, β-unsaturated nitrile compound include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile, vinylidene cyanide, etc., and use one or more selected from these. Can do. Among these, at least one selected from the group consisting of acrylonitrile and methacrylonitrile is preferable, and acrylonitrile is particularly preferable.

In the polymer (A), when the repeating unit (a2) is included, the content ratio is preferably 1 to 50 parts by mass when the total of all the repeating units is 100 parts by mass, and 5 to 20 parts by mass. More preferably. When the content ratio of the repeating unit (a2) in the polymer (A) is within the above range, the binding property can be further improved.
1.1.1.3. Repeating unit derived from unsaturated carboxylic acid (a3)
The polymer (A) may contain a repeating unit (a3) derived from an unsaturated carboxylic acid. When the repeating unit (a3) derived from an unsaturated carboxylic acid is used, the affinity with the electrolytic solution is improved, and the increase in internal resistance due to the polymer particles becoming an electrical resistance component in the electricity storage device is suppressed. A decrease in binding due to excessive absorption of the electrolytic solution can be prevented.
Although it does not specifically limit as repeating unit (a3) originating in unsaturated carboxylic acid, Specifically, monocarboxylic acid or dicarboxylic acid, such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, is used. One or more selected from these can be used. As the unsaturated carboxylic acid, it is preferable to use one or more selected from acrylic acid and methacrylic acid, and acrylic acid is particularly preferable.

In the polymer (A), when the repeating unit (a3) is included, the content ratio is preferably 1 to 99 parts by mass when the total of all the repeating units is 100 parts by mass, and 10 to 90 parts by mass. More preferably. When the content ratio of the repeating unit (a3) in the polymer (A) is in the above range, the binding property can be further improved.
1.1.1.4. Repeating unit containing fluorine atom (a4)
The polymer (A) may contain a repeating unit (a4) containing a fluorine atom. When the repeating unit (a4) containing a fluorine atom is used, adhesion and flexibility can be expressed without deteriorating oxidation resistance.
Although it does not specifically limit as repeating unit (a4) containing a fluorine atom, Specifically, the olefin compound which has a fluorine atom, the (meth) acrylic acid ester which has a fluorine atom, etc. are mentioned. Examples of the olefin compound having a fluorine atom include vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, ethylene trifluoride chloride, and perfluoroalkyl vinyl ether. Examples of the (meth) acrylic acid ester having a fluorine atom include (meth) acrylic acid 3 [4 [1-trifluoromethyl-2,2-bis [bis (trifluoromethyl) fluoromethyl] ethynyloxy] benzooxy] 2 -Hydroxypropyl and the like.

In the polymer (A), when the repeating unit (a4) is included, the content ratio is preferably 1 to 90 parts by mass when the total of all repeating units is 100 parts by mass, and 10 to 30 parts by mass. More preferably. When the content ratio of the repeating unit (a4) in the polymer (A) is in the above range, the binding property can be further improved.
<Aspects of fluorinated polymer particles>
Specific embodiments of the fluorine-containing polymer particles include (1) copolymer particles obtained by synthesizing polymer particles (A1) having a repeating unit derived from a monomer having a fluorine atom by one-step polymerization. And (2) composite particles having a polymer X having a repeating unit derived from a monomer having a fluorine atom and a polymer Y having a repeating unit derived from an unsaturated carboxylic acid. Among these, from the viewpoint of excellent oxidation resistance, composite particles are preferable, and the composite particles are more preferably polymer alloy particles. As a manufacturing method, it can obtain by the method as described in patent publication 2014-081996 grade | etc.,.
1.1.1.5. Other unsaturated carboxylic acid ester monomers (a5)
The polymer (A) may contain other unsaturated carboxylic acid ester monomer (a5). Other unsaturated monomers (a5) can be appropriately used for the purpose of obtaining desired performance. For example, it has good affinity with the electrolyte and suppresses the increase in internal resistance due to the binder becoming an electrical resistance component in the electricity storage device, and also prevents the decrease in binding due to excessive absorption of the electrolyte The other unsaturated carboxylic acid ester monomer (a5) is not particularly limited. For example, it is an unsaturated carboxylic acid ester (provided that the compound has two or more polymerizable unsaturated groups and the fluorine atom). Except those corresponding to monomers), aromatic vinyl compounds (except those corresponding to compounds having two or more polymerizable unsaturated groups) and other monomers.

  As unsaturated carboxylic acid ester, (meth) acrylic acid ester can be used preferably, for example, alkyl ester of (meth) acrylic acid. The alkyl ester of (meth) acrylic acid is preferably an alkyl ester of (meth) acrylic acid having an alkyl group having 1 to 10 carbon atoms, such as methyl (meth) acrylate, ethyl (meth) acrylate, (meth ) N-propyl acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, n- (meth) acrylate Amyl, i-amyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, etc. Is mentioned. The unsaturated carboxylic acid ester exemplified above may be used alone or in combination of two or more. Among these, it is preferable that it is an alkyl ester of (meth) acrylic acid, from (meth) acrylic acid methyl, (meth) acrylic acid ethyl, (meth) acrylic acid n-butyl, and (meth) acrylic acid 2-ethylhexyl. It is more preferable to use one or more selected.

  Other monomers include alkyl amides of ethylenically unsaturated carboxylic acids such as (meth) acrylamide and N-methylol acrylamide; carboxylic acid vinyl esters such as vinyl acetate and vinyl propionate; acids of ethylenically unsaturated dicarboxylic acids Monoalkyl ester; Monoamide; Aminoalkylamide of ethylenically unsaturated carboxylic acid such as aminoethylacrylamide, dimethylaminomethylmethacrylamide, methylaminopropylmethacrylamide, etc .; Vinylsulfonic acid, styrenesulfonic acid, allylsulfonic acid, sulfone Ethyl methacrylate, sulfopropyl methacrylate, sulfobutyl methacrylate, 2-acrylamido-2-methylpropanesulfonic acid, 2-hydroxy-3-acrylamidopropanesulfonic acid, 3-a Can be exemplified compounds having a sulfonic acid group such as a proxy-2-hydroxypropane sulfonic acid, may be used one or more selected from these.

In the polymer (A), when the repeating unit (a5) is included, the content ratio is preferably 5 to 50 parts by mass when the total of all the repeating units is 100 parts by mass, and 10 to 30 parts by mass. More preferably. When the content ratio of the repeating unit (a5) in the polymer (A) is in the above range, the binding property can be further improved.
1.1.1.6. Repeating units derived from conjugated diene compounds (a6)
The polymer (A) may contain a repeating unit (a6) derived from a conjugated diene compound. When the repeating unit (a6) derived from the conjugated diene compound is contained, it is preferable because appropriate flexibility can be imparted and the binding property between the polymer particles becomes good.
Although it does not specifically limit as a repeating unit (a6) derived from a conjugated diene compound, A conjugated diene compound, an aromatic vinyl compound, etc. can be mentioned specifically.
Although it does not specifically limit as a conjugated diene compound, Specifically, 1, 3- butadiene, 2-methyl- 1, 3- butadiene, 2, 3- dimethyl- 1, 3- butadiene, 2-chloro- 1, 3- Butadiene can be used, and one or more selected from these can be used. Among these, 1,3-butadiene is particularly preferable.
Specific examples of the aromatic vinyl compound include styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, chlorostyrene, and the like, and can be one or more selected from these. Among the above, the aromatic vinyl compound is particularly preferably styrene.

In the polymer (A), when the repeating unit (a6) is included, the content ratio is preferably 5 to 50 parts by mass when the total of all repeating units is 100 parts by mass, and 10 to 30 parts by mass. More preferably. When the content ratio of the repeating unit (a6) in the polymer (A) is in the above range, the binding property can be further improved.
1.1.1.7. Aromatic polyfunctional vinyl compound (a7)
The polymer (A) may contain an aromatic polyfunctional vinyl compound (a7). When the aromatic polyfunctional vinyl compound (a7) is contained, it is preferable because appropriate flexibility can be imparted and the binding property between the polymer particles becomes good.

  Examples of the aromatic polyfunctional vinyl compound (a7) include aromatic divinyl compounds such as divinylbenzene and diisopropenylbenzene, but are not limited thereto. Of these, divinylbenzene is preferred. The aromatic polyfunctional vinyl compounds exemplified above may be used alone or in combination of two or more.

In the polymer (A), when the repeating unit (a7) is included, the content ratio is preferably 0.1 to 50 parts by mass when the total of all the repeating units is 100 parts by mass, and 1 to 20 parts by mass. More preferably, it is a part. When the content ratio of the repeating unit (a7) in the polymer (A) is in the above range, the binding property can be further improved.
1.1.1.8. Molecular weight regulator (a8)
Examples of the molecular weight modifier (a8) include alkyl mercaptans such as n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-stearyl mercaptan; dimethylxanthogen disulfide, diisopropylxanthogen Xanthogen compounds such as disulfide; thiuram compounds such as terpinolene, tetramethylthiuram disulfide, tetraethylthiuram disulfide and tetramethylthiuram monosulfide; phenol compounds such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol Allyl compounds such as allyl alcohol; halogenated hydrocarbon compounds such as dichloromethane, dibromomethane and carbon tetrabromide; α-benzyl In addition to vinyl ether compounds such as xylstyrene, α-benzyloxyacrylonitrile, α-benzyloxyacrylamide, etc., triphenylethane, pentaphenylethane, acrolein, methacrolein, thioglycolic acid, thiomalic acid, 2-ethylhexylthioglycolate, α- Examples thereof include, but are not limited to, methylstyrene dimer. Of these, dodecyl mercaptan is preferred. The above exemplified molecular weight regulators may be used alone or in combination of two or more.

  In the polymer (A), when the repeating unit (a8) is included, the content ratio is preferably 0.1 to 50 parts by mass when the total of all the repeating units is 100 parts by mass, and 1 to 20 parts by mass. More preferably, it is a part. When the content ratio of the repeating unit (a8) in the polymer (A) is within the above range, the binding property can be further improved.

1.1.2. Number average particle diameter of polymer (A) (Da1)
When the polymer (A) is a particle, the number average particle diameter (Da1) of the polymer particle is preferably in the range of 20 to 450 nm, more preferably in the range of 30 to 420 nm, and 50 to 400 nm. It is especially preferable that it is in the range.

  When the number average particle diameter (Da1) of the polymer particles is in the above range, the stability of the composition for an electricity storage device is improved, and the internal resistance is increased even when a protective film is formed on the electrode or separator (resistance increase rate). ) Can be kept low.

  The number average particle size (Da1) of the polymer particles is a particle size distribution measuring apparatus using a light scattering method as a measurement principle, and a cumulative frequency of the number of particles when particles are accumulated from small particles. The particle diameter (D50) is 50%. Examples of such a particle size distribution measuring apparatus include Coulter LS230, LS100, LS13320 (above, manufactured by Beckman Coulter. Inc), FPAR-1000 (manufactured by Otsuka Electronics Co., Ltd.), and the like. These particle size distribution measuring devices are not intended to evaluate only the primary particles of the polymer particles, but can also evaluate the secondary particles formed by aggregation of the primary particles. Therefore, the particle size distribution measured by these particle size distribution measuring devices can be used as an indicator of the dispersion state of the polymer particles contained in the composition.

1.1.3. A polyamic acid and its imidized polymer The polymer (A) contained in the composition for electrical storage devices which concerns on this embodiment contains at least 1 sort (s) selected from the group which consists of a polyamic acid and its imidized polymer. Also good. A polyamic acid can be obtained by reacting a tetracarboxylic dianhydride and a diamine. Moreover, the partially imidized product of polyamic acid can be obtained by dehydrating and ring-closing a part of the amic acid structure of the polyamic acid to imidize it.

  Although it does not specifically limit as tetracarboxylic dianhydride and diamine used in order to synthesize polyamic acid, Specifically, tetracarboxylic dianhydride and diamine as described in Unexamined-Japanese-Patent No. 2010-97188 etc. should be used. Can do. Polyamic acid and its imidized polymer can be synthesized by the method described in Japanese Patent No. 5099394.

1.1.4. Molecular weight of polymer (A) Polymerization average molecular weight (Mw) of the polymer (A) is preferably 10,000 or more, more preferably 100,000 or more, particularly preferably 5000000 or more. When the molecular weight of the polymer (A) is within the above range, it contains adhesion with an electrode having good charge / discharge characteristics.

1.1.5. Endothermic characteristics of polymer (A) When polymer (A) is subjected to differential scanning calorimetry (DSC) according to JIS K7121, only one endothermic peak in the temperature range of −50 to + 80 ° C. is observed. It is preferred that The endothermic behavior of the polymer (A) is presumed to correlate with the shape stability of the polymer particles. For this reason, if the endothermic peak of a polymer (A) is the said temperature range, it will be estimated that the shape stability of the said polymer will become favorable and the formed protective film can have sufficient intensity | strength.

1.1.6. Production method of polymer (A) When the polymer (A) is a fluorine-containing polymer particle, its production, that is, a polymer having a repeating unit derived from a monomer having a fluorine atom is obtained by one-step polymerization. In the synthesis, the polymerization of the polymer X, and the polymerization of the polymer Y in the presence of the polymer X are carried out in the presence of a known polymerization initiator, molecular weight regulator, emulsifier (surfactant), etc., respectively. It can be carried out.

  Further, when the polymer (A) is a diene polymer particle, it may be prepared by one-stage polymerization, may be prepared by two-stage polymerization, and further by multi-stage polymerization. In each polymerization, a known polymerization initiator, It can be carried out in the presence of a molecular weight regulator, an emulsifier (surfactant) and the like.

1.2. Resin (B) having a repeating unit having an alicyclic hydrocarbon group of 50% by mass or more and a polymerization average molecular weight (Mw) of less than 10,000
The binder composition for an electricity storage device according to this embodiment contains a resin (B) having a repeating unit having an alicyclic hydrocarbon group of 50% by mass or more and a polymerization average molecular weight (Mw) of less than 10,000. Since the resin (B) has high hydrophobicity, it is presumed that it contributes to improvement in adhesion to a separator that is a hydrophobic material.

  Such a resin (B) will not be specifically limited if the repeating unit which has an alicyclic hydrocarbon group is 50 mass% or more, and a polymerization average molecular weight (Mw) is less than 10,000. As resin (B), even if it is resin which consists only of a repeating unit which has an alicyclic hydrocarbon group, it may contain other repeating units, for example.

  Although the repeating unit having an alicyclic hydrocarbon group is not particularly limited, specifically, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, di Cyclopentenyloxyethyl (meth) acrylate, 1,3-adamantanediol di (meth) acrylate, 1,3-adamantane dimethanol di (meth) acrylate, 2-methyl-2-adamantyl (meth) acrylate, 2-ethyl Examples include 2-adamantyl (meth) acrylate, 3-hydroxy-1-adamantyl (meth) acrylate, and 1-adamantyl (meth) acrylate. Moreover, the repeating unit obtained by hydrogenating the repeating unit which has an aromatic hydrocarbon group after superposition | polymerization may be sufficient. Such repeating units are not particularly limited, and specific examples include hydrogenated indene, hydrogenated dicyclopentadiene, hydrogenated vinyltoluene, hydrogenated styrene, hydrogenated methylstyrene, and the like. These repeating units may be used alone or in combination of two or more.

  The resin (B) preferably has 50% by mass or more of repeating units having an alicyclic hydrocarbon group, more preferably 55% by mass or more, and still more preferably 60% by mass or more. When the repeating unit having an alicyclic hydrocarbon group is in the above range, the hydrophobicity of the resin (B) increases, and it becomes easy to contribute to the improvement of the adhesion with the separator that is a hydrophobic material.

  As the resin (B), a commercially available resin can be used. For example, AM-1000-NT, M-100, M-135 (above, manufactured by Arakawa Chemical Co., Ltd.), HB125 (manufactured by TonenGeneral Co., Ltd.), Quintone 1500 (manufactured by Nippon Zeon Co., Ltd.) and the like can be mentioned. Among these, AM-1000-NT, M-100, and HB125 are preferable from the viewpoint of improving adhesion.

  The polymerization average molecular weight (Mw) of the resin (B) is preferably less than 10,000, more preferably 9000 or less, and still more preferably 8000 or less. When the polymerization average molecular weight (Mw) of the resin (B) is in the above range, the compatibility with the polymer (A) tends to be good. Moreover, as a minimum of the polymerization average molecular weight (Mw) of resin (B), 1000 or more are preferable, 2000 or more are more preferable, and 3000 or more are still more preferable. When the polymerization average molecular weight (Mw) of the resin (B) is in the above range, elution of the resin (B) into the electrolytic solution is suppressed, and charge / discharge characteristics are likely to be good.

  When forming or laminating a protective film or an electrode on the separator surface using the binder composition for an electricity storage device according to this embodiment, the content of the polymer (A) is Ma parts by mass, and the resin (B) is contained. When the amount is Mb part by mass, Mb / Ma is preferably in the range of 0.1 to 20, more preferably in the range of 0.2 to 13. When Mb / Ma is in the above range, the polymer (A) and the resin (B) form a structural body that is appropriately compatible, so that the polymer (A) is strong with a separator having hydrophobic surface characteristics. It can be inferred that it is closely attached to. As a result, the inventor presumes that the separator can be more effectively prevented from being thermally contracted when the hole of the separator is closed during the abnormal heat generation of the electricity storage device to exhibit a shutdown function.

  When forming a protective film or an electrode on the separator surface using the binder composition for an electricity storage device according to this embodiment, the content ratio of the resin (B) is the polymer (A), a water-soluble polymer (D) described later, and It is preferably 0.5 to 15 parts by mass and more preferably 0.9 to 10 parts by mass with respect to 100 parts by mass in total of the filler (E). Within the above range, the adhesion between the resin (B) and the separator surface is improved, and the adhesion is further improved by the interaction between the polymer (A) and the resin (B).

1.3. Liquid medium (C)
The composition for an electricity storage device according to this embodiment further contains a liquid medium (C). The liquid medium (C) 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% by mass or less, and more preferably 5% by mass or less, with respect to the total amount of the aqueous medium. The aqueous medium is most preferably composed only of water without containing a non-aqueous medium.

  The composition for an electricity storage device according to the present embodiment uses an aqueous medium as the liquid medium (C), and preferably contains no non-aqueous medium other than water, so that it has a low degree of adverse effects on the environment. The safety against is increased.

1.4. Other components 1.4.1. Water-soluble polymer (D)
The composition for an electricity storage device according to the present embodiment may contain a water-soluble polymer (D) from the viewpoint of improving the coatability and adhesion. Examples of the water-soluble polymer (D) include cellulose compounds such as carboxymethylcellulose, methylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, and hydroxyethylcellulose; ammonium salts or alkali metal salts of the above cellulose compounds; poly (meth) acrylic acid, modified poly Polycarboxylic acids such as (meth) acrylic acid; alkali metal salts of the above polycarboxylic acids; polyvinyl alcohol (co) polymers such as polyvinyl alcohol, modified polyvinyl alcohol, and ethylene-vinyl alcohol copolymers; (meth) acrylic acid Saponified products of copolymers of unsaturated carboxylic acids such as maleic acid and fumaric acid with vinyl esters; alternating copolymers of maleic anhydride and isobutylene; ammonium salts of the alternating copolymers or And water-soluble polymers such as alkali metal salts. Among these, particularly preferred water-soluble polymers (D) include alkali metal salts of carboxymethyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, alkali metal salts of poly (meth) acrylic acid, and alternating copolymers of maleic anhydride and isobutylene. Alkali metal salts of

  Examples of commercially available water-soluble polymers (D) include CMC 1120, CMC 1150, CMC 2200, CMC 2280, CMC 2450 (manufactured by Daicel Corporation), Metroles SH type, Metroles SE type (manufactured by Shin-Etsu Chemical Co., Ltd.), and the like. Mention may be made of alkali metal salts of carboxymethylcellulose. In addition, examples of commercially available alternating copolymers of maleic anhydride and isobutylene include isoban 06, isoban 10, isoban 18, isoban 110 (above, manufactured by Kuraray Co., Ltd.) and the like.

1.4.2. Surfactant The composition for an electricity storage device according to the present embodiment may contain a surfactant from the viewpoint of improving dispersibility and dispersion stability. As the surfactant, a known one can be used as in “1.1.1.5. Production method of polymer (A)”.

2. Power Storage Device Slurry The power storage device slurry according to the present embodiment contains the above-described power storage device binder composition. And the above-mentioned binder composition for an electricity storage device can be used as a material for forming a protective film for suppressing a short circuit caused by dendrite that occurs in association with charge / discharge, or a combination of active materials. It can also be used as a material for producing an electricity storage device electrode (active material layer) having improved ability, adhesion between the active material and the current collector, and powder fall resistance. Therefore, a slurry for an electricity storage device for forming a protective film (hereinafter also referred to as “slurry for forming a protective film”) and a slurry for an electricity storage device for forming an active material layer of the electricity storage device electrode (hereinafter referred to as “electric storage device”). It is also referred to as “device electrode slurry”.

2.1. Protective film forming slurry In this specification, “slurry for forming a protective film” is applied to the surface of the electrode and / or separator and then dried to form a protective film on the surface of the electrode and / or separator. Refers to the dispersion used to form. The slurry for protective film formation concerning this embodiment may be comprised only from the binder composition for electrical storage devices mentioned above, and may further contain the filler (E). Hereinafter, each component contained in the slurry for forming a protective film according to this 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.

2.1.1. Filler (E)
By containing the filler (E), the slurry for forming a protective film according to the present embodiment can improve the toughness of the protective film to be formed. As the filler, an inorganic filler, an organic filler, or the like can be used, but an inorganic filler is preferably used. As the inorganic filler, it is preferable to use at least one type of particles selected from the group consisting of silica, titanium oxide (titania), aluminum oxide (alumina), zirconium oxide (zirconia), and magnesium oxide (magnesia). 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.

  It is preferable that the average particle diameter of a filler (E) is 1 micrometer or less, and it is more preferable that it exists in the range of 0.1-0.8 micrometer. In addition, it is preferable that the average particle diameter of a filler (E) 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 a filler (E) is clogged with the microporous of a separator.

  The slurry for forming a protective film according to this embodiment preferably contains 0.1 to 20 parts by mass of the above-mentioned composition for an electricity storage device in terms of solid content with respect to 100 parts by mass of the filler (E). It is more preferable that 1-10 mass parts is contained. When the content ratio of the 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 formed protective film and the lithium ion permeability is improved, and as a result, obtained. The rate of increase in resistance of the electricity storage device can be further reduced.

2.1.2. Other components In the slurry for forming a protective film according to the present embodiment, the materials and addition amounts described in “1.4. Other components” of the composition for an electricity storage device can be used as necessary. .

2.2. “Slurry for electricity storage device electrode” in this specification is 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. Refers to a dispersion. The slurry for an electricity storage device electrode according to this embodiment contains the binder composition for an electricity storage device described above and an active material (F). Hereinafter, each component contained in the slurry for an electricity storage device electrode according to the present embodiment will be described in detail. In addition, about the composition for electrical storage devices, since it is as above-mentioned, description is abbreviate | omitted.

2.2.1. Active material (F)
Examples of the active material (F) used in the power storage device electrode slurry according to the present embodiment include carbon materials, silicon materials, oxides containing lithium atoms, lead compounds, tin compounds, arsenic compounds, antimony compounds, and aluminum compounds. And so on.

  Examples of the carbon material include amorphous carbon, graphite, natural graphite, mesocarbon microbeads (MCMB), and pitch-based carbon fibers.

Examples of the silicon material include silicon simple substance, silicon oxide, and silicon alloy. For example, SiC, SiO _x C _y (0 <x ≦ 3, 0 <y ≦ 5), Si ₃ N ₄ , Si oxide complex represented by Si ₂ N ₂ O, SiO _x (0 <x ≦ 2) (for example, materials described in JP-A Nos. 2004-185810 and 2005-259697), A silicon material described in JP-A No. 2004-185810 can be used. The silicon oxide is preferably a silicon oxide represented by the composition formula SiO _x (0 <x <2, preferably 0.1 ≦ x ≦ 1). The silicon alloy is preferably an alloy of silicon and at least one transition metal selected from the group consisting of titanium, zirconium, nickel, copper, iron and molybdenum. These transition metal silicon alloys are preferably used because they have high electronic conductivity and high strength. In addition, since the active material contains these transition metals, the transition metal present on the surface of the active material is oxidized to form an oxide having a hydroxyl group on the surface, so that the binding force with the binder is further improved. preferable. As the silicon alloy, it is more preferable to use a silicon-nickel alloy or a silicon-titanium alloy, and it is particularly preferable to use a silicon-titanium alloy. The silicon content in the silicon alloy is preferably 10 mol% or more, and more preferably 20 to 70 mol%, based on all the metal elements in the alloy. Note that the silicon material may be single crystal, polycrystalline, or amorphous.

Examples of the oxide containing a lithium atom include lithium cobaltate, lithium nickelate, lithium manganate, ternary nickel cobalt lithium manganate, LiFePO ₄ , LiCoPO ₄ , LiMnPO ₄ , Li _0.90 Ti _0.05 Nb. _0.05 Fe _0.30 Co _0.30 Mn _0.30 PO _{4 and the} like.

Further, the active material exemplified below may be included in the active material layer. Examples of such an active material include a conductive polymer such as polyacene; A _X B _Y O _Z (where A is an alkali metal or transition metal, B is a transition metal such as cobalt, nickel, aluminum, tin, or manganese) At least one selected, O represents an oxygen atom, and X, Y, and Z are 1.10>X> 0.05, 4.00>Y> 0.85, 5.00>Z> 1.5, respectively. The composite metal oxide represented by (2) and other metal oxides are exemplified.

  The slurry for an electricity storage device electrode according to this embodiment can be used when producing either the positive electrode or the negative electrode electricity storage device electrode.

  When producing a positive electrode, it is preferable to use the oxide containing a lithium atom among the active materials illustrated above.

  When producing a negative electrode, it is preferable to use what contained the carbon material and the silicon material among the active materials illustrated above.

  In the case where a carbon material and a silicon material are used in combination as the active material, the silicon material is used in an amount of 4 to 40% by mass from the viewpoint of maintaining sufficient binding properties. %, More preferably 5 to 35% by mass, and particularly preferably 5 to 30% by mass. Since the volume expansion of the carbon material relative to the volume expansion of the silicon material due to occlusion of lithium is small when the amount of silicon material used is in the above range, the volume change due to charge / discharge of the active material layer containing these active materials is reduced. The binding between the current collector and the active material layer can be further improved.

  The shape of the active material is preferably granular. The average particle diameter of the active material is preferably 0.1 to 100 μm, and more preferably 1 to 20 μm.

  Here, the average particle diameter of the active material is a volume average particle diameter calculated from a particle size distribution measured by using a particle size distribution measuring apparatus based on a laser diffraction method. 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 does not only evaluate primary particles of the active material, but also evaluates secondary particles formed by aggregation of the primary particles. Therefore, the average particle diameter 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 average particle diameter of the active material can also be measured by centrifuging the slurry to settle the active material, removing the supernatant, and measuring the precipitated active material by the above method. .

  The use ratio of the active material (F) is preferably such that the content ratio of the polymer (A) with respect to 100 parts by mass of the active material is 0.1 to 25 parts by mass, It is more preferable to use it at a ratio such that it becomes part by mass. By setting it as such a usage rate, it is possible to produce an electrode that is excellent in adhesiveness and has low electrode resistance and excellent charge / discharge characteristics.

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. . Such an electricity storage device electrode can be produced by applying the above-mentioned slurry for an electricity storage device electrode on 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 (A), resin (B) and active material on the current collector, and an optional component added as necessary. It is what is bound. In such an electricity storage device electrode, the polymer (A) and the resin (B) are appropriately compatible to improve the adhesion between the base material having various surface characteristics and the active material layer. Thereby, while being excellent in the adhesiveness of an electrical power collector and a separator, and an active material layer, the charging / discharging rate characteristic which is one of the electrical characteristics becomes favorable.

  The current collector is not particularly limited as long as it is made of a conductive material. In a lithium ion secondary battery, a current collector made of metal such as iron, copper, aluminum, nickel, and stainless steel is used. In particular, when aluminum is used for the positive electrode and copper is used for the negative electrode, the above-described storage device electrode The effect of the slurry 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 hot air, hot air or 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). Hereinafter, preferred embodiments of an electricity storage device according to the present invention will be described in detail with reference to the drawings. 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 for forming the protective film described above. It is produced using a slurry. Hereinafter, first to third embodiments will be described with reference to the drawings.

4.1. First Embodiment FIG. 1 is a schematic view showing a cross section of an electricity storage device according to a first embodiment. As shown in FIG. 1, the electricity storage device 1 includes a positive electrode 10 in which a positive electrode active material layer 14 is formed on the surface of a positive electrode current collector 12 and a negative electrode 20 in which a negative electrode active material layer 24 is formed on the surface of a negative electrode current collector 22. And a protective film 30 provided between the positive electrode 10 and the negative electrode 20, and an electrolyte solution 40 that fills between the positive electrode 10 and the negative electrode 20. In the electricity storage device 1, no separator is provided between the positive electrode 10 and the negative electrode 20. This is because if the positive electrode 10 and the negative electrode 20 are completely fixed with a solid electrolyte or the like, the positive electrode 10 and the negative electrode 20 do not come into contact with each other to cause a short circuit.

  The positive electrode 10 shown in FIG. 1 is formed so that the positive electrode active material layer 14 is not provided on one surface along the longitudinal direction and the positive electrode current collector 12 is exposed. A layer 14 may be provided. Similarly, the negative electrode 20 shown in FIG. 1 is formed such that the negative electrode active material layer 24 is not provided on one surface along the longitudinal direction and the negative electrode current collector 22 is exposed, A negative electrode active material layer 24 may be provided.

  As the positive electrode current collector 12, for example, a metal foil, an etching metal foil, an expanded metal, or the like can be used. Specific examples of these materials include metals such as aluminum, copper, nickel, tantalum, stainless steel, and titanium, and can be appropriately selected and used according to the type of the target power storage device. For example, when forming the positive electrode of a lithium ion secondary battery, it is preferable to use aluminum among the above as the positive electrode current collector 12. In such a case, the thickness of the positive electrode current collector 12 is preferably 5 to 30 μm, and more preferably 8 to 25 μm.

  The positive electrode active material layer 14 includes one or more positive electrode active materials of a positive electrode material that can be doped / dedoped with lithium, and is configured to include a conductivity-imparting agent such as graphite as necessary. . In addition, as a binder, a thickener used for dispersion of a fluorine-containing polymer such as polyvinylidene fluoride or polyfluorinated acrylate or a positive electrode active material, or a styrene butadiene rubber (SBR) or (meth) acrylate copolymer A polymer composition containing a coalescence may be used. These binders may use only 1 type and may mix and use 2 or more types.

  As the negative electrode current collector 22, for example, a metal foil, an etching metal foil, an expanded metal, or the like can be used. Specific examples of these materials include metals such as aluminum, copper, nickel, tantalum, stainless steel, and titanium, and can be appropriately selected and used according to the type of the target power storage device. Of the above, copper is preferably used as the negative electrode current collector 22. In such a case, the thickness of the current collector is preferably 5 to 30 μm, and more preferably 8 to 25 μm.

  The negative electrode active material layer 24 is configured to include any one or two or more negative electrode materials that can be doped / undoped with lithium as a negative electrode active material, and if necessary, a binder similar to the positive electrode It is comprised including.

Note that the above-described active material layer is preferably subjected to press working. Examples of means for performing the press working include a roll press machine, a high-pressure super press machine, a soft calendar, and a 1-ton press machine. The conditions for the press working are appropriately set according to the type of processing machine used and the desired thickness and density of the active material layer. In the case of a lithium ion secondary battery positive electrode, the thickness is preferably 40 to 100 μm and the density is preferably 2.0 to 5.0 g / cm ³ . In the case of a lithium ion secondary battery negative electrode, the thickness is preferably 40 to 100 μm and the density is preferably 1.3 to 1.9 g / cm ³ .

  The protective film 30 is disposed between the positive electrode 10 and the negative electrode 20. 1, the protective film 30 is disposed between the positive electrode 10 and the negative electrode 20 so as to be in contact with the positive electrode active material layer 14, but is disposed so as to be in contact with the negative electrode active material layer 24. May be. The protective film 30 may be disposed as a self-supporting film between the positive electrode 10 and the negative electrode 20 without being in contact with the positive electrode 10 or the negative electrode 20. Thereby, even if it is a case where dendrites precipitate by repeating charging / discharging, since it is guarded by the protective film 30, a short circuit does not occur. Therefore, the function as an electricity storage device can be maintained.

  The protective film 30 can be formed, for example, by applying the above-described protective film-forming slurry to the surface of the positive electrode 10 (or the negative electrode 20) and drying it. For example, a doctor blade method, a reverse roll method, a comma bar method, a gravure method, an air knife method, a die coating method, or the like is applied as a method for applying the protective film forming slurry to the surface of the positive electrode 10 (or the negative electrode 20). Can do. The drying treatment of the coating film is preferably performed in a temperature range of 20 to 250 ° C., more preferably 50 to 150 ° C., preferably for a processing time of 1 to 120 minutes, more preferably 5 to 60 minutes.

  Although the film thickness of the protective film 30 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 30 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 40 is appropriately selected and used according to the type of the target power storage device. As the electrolytic solution 40, a solution in which an appropriate electrolyte is dissolved in a solvent is used.

When manufacturing a lithium ion secondary battery, a lithium compound is used as an electrolyte. Specifically, for example _{LiClO 4, LiBF 4, LiI,} LiPF 6, LiCF 3 SO 3, LiAsF 6, LiSbF 6, LiAlCl 4, LiCl, LiBr, LiB (C 2 H 5) 4, LiCH 3 SO 3, LiC _{4 F 9 SO 3, Li (} CF 3 SO 2) can be cited ₂ N or the like. The electrolyte concentration in this case is preferably 0.5 to 3.0 mol / L, more preferably 0.7 to 2.0 mol / L.

  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.

  In any of the above cases, examples of the solvent used in the electrolytic solution include carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; lactones such as γ-butyrolactone; trimethoxy Silane, 1,2-dimethoxyethane, diethyl ether, 2-ethoxyethane, tetrahydrofuran, ether such as 2-methyltetrahydrofuran; Sulfoxide such as dimethyl sulfoxide; 1,3-dioxolane, 4-methyl-1,3-dioxolane, etc. Oxolane derivatives; nitrogen-containing compounds such as acetonitrile and nitromethane; esters such as methyl formate, methyl acetate, butyl acetate, methyl propionate, ethyl propionate, and phosphate triester Glyme compounds such as diglyme, triglyme and tetraglyme; ketones such as acetone, diethyl ketone, methyl ethyl ketone and methyl isobutyl ketone; sulfone compounds such as sulfolane; oxazolidinone derivatives such as 2-methyl-2-oxazolidinone; 1,3-propane sultone; Examples include sultone compounds such as 1,4-butane sultone, 2,4-butane sultone, and 1,8-naphtha sultone.

4.2. Second Embodiment FIG. 2 is a schematic view showing a cross section of an electricity storage device according to a second embodiment. As shown in FIG. 2, the electricity storage device 2 includes a positive electrode 110 in which a positive electrode active material layer 114 is formed on the surface of a positive electrode current collector 112 and a negative electrode 120 in which a negative electrode active material layer 124 is formed on the surface of a negative electrode current collector 122. A protective film 130 provided between the positive electrode 110 and the negative electrode 120, an electrolyte solution 140 that fills between the positive electrode 110 and the negative electrode 120, and a separator 150 provided between the positive electrode 110 and the negative electrode 120. It is provided.

  The electricity storage device 2 is different from the electricity storage device 1 described above in that the protective film 130 is disposed so as to be sandwiched between the positive electrode 110 and the separator 150. In the power storage device 2 illustrated in FIG. 2, the protective film 130 is disposed so as to be sandwiched between the positive electrode 110 and the separator 150, but the protective film 130 is sandwiched between the negative electrode 120 and the separator 150. It may be arranged so that. By adopting such a configuration, even when dendrite is deposited by repeated charge and discharge, the protective film 130 guards and no short circuit occurs. Therefore, the function as an electricity storage device can be maintained.

  The protective film 130 can be formed by, for example, applying a slurry for forming a protective film on the surface of the separator 150, bonding the positive electrode 110 (or the negative electrode 120), and then drying. As a method of applying the protective film-forming slurry to the surface of the separator 150, for example, a doctor blade method, a reverse roll method, a comma bar method, a gravure method, an air knife method, a die coating method, or the like can be applied. The drying treatment of the coating film is preferably performed in a temperature range of 20 to 250 ° C., more preferably 50 to 150 ° C., preferably for a processing time of 1 to 120 minutes, more preferably 5 to 60 minutes.

  Any separator 150 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 2 according to the second embodiment is the same as that of the power storage device 1 according to the first embodiment described with reference to FIG.

4.3. Third Embodiment FIG. 3 is a schematic view showing a cross section of an electricity storage device according to a third embodiment. As shown in FIG. 3, the electricity storage device 3 includes a positive electrode 210 in which a positive electrode active material layer 214 is formed on the surface of a positive electrode current collector 212, and a negative electrode 220 in which a negative electrode active material layer 224 is formed on the surface of a negative electrode current collector 222. An electrolyte 240 filling between the positive electrode 210 and the negative electrode 220, a separator 250 provided between the positive electrode 210 and the negative electrode 220, and a protective film 230 formed so as to cover the surface of the separator 250. It is provided.

  The electricity storage device 3 is different from the electricity storage device 1 and the electricity storage device 2 described above in that the protective film 230 is formed so as to cover the surface of the separator 250. By adopting such a configuration, even when dendrites are deposited by repeated charge and discharge, the protective film 230 guards the short circuit. Therefore, the function as an electricity storage device can be maintained.

  The protective film 230 can be formed, for example, by applying a slurry for forming a protective film on the surface of the separator 250 and drying it. As a method for applying the protective film-forming slurry to the surface of the separator 250, for example, a doctor blade method, a reverse roll method, a comma bar method, a gravure method, an air knife method, a die coating method, or the like can be applied. The drying treatment of the coating film is preferably performed in a temperature range of 20 to 250 ° C., more preferably 50 to 150 ° C., preferably for a processing time of 1 to 120 minutes, more preferably 5 to 60 minutes.

  Regarding other configurations of the power storage device 3 according to the third embodiment, the power storage device 1 according to the first embodiment described with reference to FIG. 1 and the power storage according to the second embodiment described with reference to FIG. Since it is the same as the device 2, the description thereof is omitted.

4.4. As a method of manufacturing an electricity storage device as described above, for example, two electrodes (two of a positive electrode and a negative electrode, or two of electrodes for a capacitor) are stacked with a separator as necessary, Examples include a method in which this is wound or folded in accordance with the shape of the battery and placed in a battery container, and an electrolytic solution is injected into the battery container and sealed. 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.

4.5. Applications The power storage devices as described above can be applied to lithium ion secondary batteries, electric double layer capacitors, lithium ion capacitors, and the like that require discharging at a large current density. Among these, a lithium ion secondary battery is particularly preferable. As the member other than the binder composition in the electrode and the electricity storage device of the present invention, a known member for a lithium ion secondary battery, an electric double layer capacitor, or a lithium ion capacitor can be used.

5. EXAMPLES Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. “Part” and “%” in Examples and Comparative Examples are based on mass unless otherwise specified.

5.1. Synthesis of polymer (A) 5.1.1. Synthesis example 1
<Synthesis of Polymer X>
The inside of an autoclave having an internal volume of 6 L equipped with an electromagnetic stirrer was sufficiently purged with nitrogen, then 2.5 L of deoxygenated pure water and 25 g of ammonium perfluorodecanoate as an emulsifier were charged, and the mixture was stirred at 350 rpm up to 60 ° C. The temperature rose. Next, a mixed gas consisting of 70% by mass of vinylidene fluoride (VDF) and 30% by mass of propylene hexafluoride (HFP) as monomers was charged until the internal pressure reached 20 kg / cm ² . 25 g of Freon 113 (CClF ₂ -CCl ₂ F) 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% by mass of VDF and 39.8% by mass of HFP was sequentially injected so that the internal pressure was maintained at 20 kg / cm ² , and the pressure was maintained at 20 kg / cm ² . In addition, 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. Then, simultaneously with cooling the reaction liquid, the stirring was stopped, and after the unreacted monomer was released, the reaction was stopped to obtain an aqueous dispersion containing 40% by mass of the polymer X particles. As a result of analyzing the obtained polymer X by ¹⁹ F-NMR, the mass composition ratio of each monomer was VDF / HFP = 21/4.
<Synthesis of polymer particles (A1)>
After the inside of the 7-liter separable flask was sufficiently purged with nitrogen, 20 parts by mass of an aqueous dispersion containing the particles of the polymer X obtained in the above step in terms of the polymer X, emulsifier “ADEKA rear soap SR1025” (Trade name, manufactured by ADEKA Corporation) 0.4 parts by mass, isobonyl methacrylate (IMA) 40 parts by mass, 2-ethylhexyl acrylate (EHA) 34 parts by mass, acrylic acid (AA) 4 parts by mass, and ethylene glycol di 2 parts by weight of methacrylate (EDMA) and 104 parts by weight of water were sequentially added and stirred at 70 ° C. for 3 hours to allow the polymer X to absorb the monomer. Next, 20 mL of a tetrahydrofuran solution containing 0.5 part by mass of azobisisobutyronitrile, which is an oil-soluble polymerization initiator, is added, heated to 75 ° C., reacted for 3 hours, and further reacted at 85 ° C. for 2 hours. went. Thereafter, the reaction was stopped after cooling, and the aqueous dispersion containing 40% by mass of the polymer (A1) containing the polymer X and the polymer Y was adjusted to pH 7 with a 2.5N aqueous sodium hydroxide solution. Obtained.

  About the aqueous dispersion obtained above, the particle size distribution is measured using a particle size distribution measuring apparatus (model “FPAR-1000” manufactured by Otsuka Electronics Co., Ltd.) having a dynamic light scattering method as a measurement principle, and the particle size distribution is obtained. The number average particle diameter (Da1) was determined from the result of 330 nm.

  10 g of the aqueous dispersion obtained above was weighed into a Teflon (registered trademark) petri dish having a diameter of 8 cm and dried at 120 ° C. for 1 hour to form a film. 1 g of the obtained film (polymer) was mixed with ethylene carbonate and diethyl carbonate (EC / DEC = 1/2 (capacity ratio)) used as an electrolytic solution in the production of an electricity storage device described later. The mixture was referred to as “EC / DEC”.) It was immersed in 400 mL and shaken at 60 ° C. for 24 hours. Next, after filtering through a 300-mesh wire mesh to separate the insoluble matter, the weight (Y (g)) of the residue obtained by evaporating and removing the dissolved EC / DEC was used to calculate the following formula (1 ), The electrolyte solution insoluble matter was found to be 98% by mass. Further, after EC / DEC attached to the surface of the insoluble matter (film) separated by the above filtration was absorbed by paper and removed, the weight of the insoluble matter film (Z (g)) was measured, and the following formula ( When the electrolytic solution swelling degree was measured by 2), the electrolytic solution swelling degree of the polymer particles was 300% by mass.

Electrolyte insoluble matter (mass%) = ((1-Y) / 1) × 100 (1)
Electrolytic solution swelling degree (% by mass) = (Z / (1-Y)) × 100 (2)
Furthermore, when the obtained film (film composed of the polymer (A1)) was measured with a differential scanning calorimeter (manufactured by NETZSCH, DSC204F1 Phoenix), the melting temperature Tm was not observed, and the single glass transition temperature was observed. Since Tg was observed at 30 ° C., the obtained polymer (A1) is presumed to be polymer alloy particles.

The weight average molecular weight (Mw) of the polymer (A) obtained above was measured under the following conditions. The weight average molecular weight (Mw) was 2 × 10 ⁶ , and the value (dispersion ratio) of weight average molecular weight (Mw) / number average molecular weight (Mn) was 10.
・ Measurement equipment: GPC (model number: HLC-8220) manufactured by Tosoh Corporation
Column: TSKgel guardcolumn HHR (manufactured by Tosoh Corporation), TSK-GEL G2500PWXL (manufactured by Tosoh Corporation), TSK-GEL GMHHR-H (manufactured by Tosoh Corporation)
Eluent: Toluene Calibration curve: Standard polystyrene Measurement method: Dissolved in the eluent so that the concentration of the polymer (A) is 0.3 wt%, and measured after filter filtration.

5.1.2. Synthesis example 2
90 parts by mass of water and 0.2 parts by mass of sodium dodecylbenzenesulfonate were charged into a 7-liter separable flask, and the inside of the separable flask was sufficiently purged with nitrogen.

  On the other hand, in a separate container, 60 parts by mass of water, ether sulfate type emulsifier (trade name “ADEKA rear soap SR1025”, manufactured by ADEKA Co., Ltd.) as an emulsifier, 0.8 parts by mass in terms of solid content, and methacryl as a monomer 10 parts by mass of cyclohexyl acid (CHMA), 10 parts by mass of acrylonitrile (AN), 10 parts by mass of methyl methacrylate (MMA), 60 parts by mass of 2-ethylhexyl acrylate (EHA), 8 parts by mass of acrylic acid (AA) and trimethacrylic acid 2 parts by mass of acid trimethylolpropane (TMPTMA) was added and stirred sufficiently to prepare a monomer emulsion containing the mixture of the above monomers.

  When the temperature inside the separable flask was started and the internal temperature reached 60 ° C., 0.5 parts by mass of ammonium persulfate was added as a polymerization initiator. Then, when the temperature inside the separable flask reaches 70 ° C., the addition of the monomer emulsion prepared above is started, and the temperature inside the separable flask is maintained at 70 ° C. The emulsion was added slowly over 3 hours. Thereafter, the temperature inside the separable flask was raised to 85 ° C., and this temperature was maintained for 3 hours to carry out the polymerization reaction. After 3 hours, the separable flask was cooled to stop the reaction, and then the aqueous dispersion containing 40% by mass of the particulate polymer (A2) was prepared by adding ammonium water to adjust the pH to 7.6. Obtained.

  Various evaluations were performed in the same manner as in Synthesis Example A1, using the aqueous dispersion containing the polymer (A2). The evaluation results are shown in Table 1.

5.1.3. Synthesis Example 3 to Synthesis Example 5
In the synthesis example A2, a polymer having a solid content concentration of 30% by mass (polymer (A3)) was prepared in the same manner as in the synthesis example A2 except that the types and amounts of the respective monomers were as shown in Table 1. To (A5)) were prepared, and an aqueous dispersion containing the particles was prepared, and various evaluations were performed in the same manner as in Synthesis Example A1. The evaluation results are shown in Table 1.
5.1.4. Synthesis Example 6
In a temperature-controllable autoclave with a stirrer, 300 parts by mass of ion exchange water, 1.5 parts by mass of sodium dodecylbenzenesulfonate, 0.5 parts by mass of potassium persulfate, 0.1 parts by mass of sodium bisulfite, α-methyl Styrene dimer 0.1 parts by weight, dodecyl mercaptan 0.1 parts by weight, acrylonitrile 10 parts by weight, acrylic acid 2 parts by weight, methacrylic acid 2 parts by weight, methyl methacrylate 11 parts by weight, 1,3-butadiene 40 parts by weight, After 35 parts by mass of styrene was added and sufficiently stirred, the mixture was heated to 45 ° C. and allowed to react for 24 hours. Thereafter, 0.5 part by mass of potassium persulfate was added and the temperature was raised to 70 ° C. and reacted for 4 hours. The polymerization conversion rate determined from the solid content concentration was about 99%. After cooling to 40 ° C., the pH of the latex is adjusted to 7.5 with sodium hydroxide, the residual monomer and water are evaporated under reduced pressure, and an aqueous dispersion containing 40% of the polymer (A6) is obtained. Produced. Various evaluations were performed in the same manner as in Synthesis Example A1, using the obtained aqueous dispersion containing the polymer (A6). The evaluation results are shown in Table 1.

5.1.5. Synthesis Example 7 to Synthesis Example 9
In the synthesis example 6, a polymer having a solid content concentration of 40% by mass (polymer (A7)) was prepared in the same manner as in the synthesis example 6 except that the types and amounts of the respective monomers were as shown in Table 1. An aqueous dispersion containing particles consisting of (A9) was prepared, and various evaluations were performed in the same manner as in Synthesis Example A1. The evaluation results are shown in Table 1.

5.1.6. Synthesis Example 10
After fully replacing the inside of a 7 L separable flask with nitrogen, after charging 75 parts by mass of ion-exchanged water and 0.05 parts by mass of an emulsifier “Rikasurf M-30” (trade name, manufactured by Shin Nippon Rika Co., Ltd.) The temperature was raised to 75 ° C. Separately from the above separable flask, an emulsifier “Rikasurf M-30” (trade name, manufactured by Shin Nippon Rika Co., Ltd.) 0.5 part by mass, tert-butyl methacrylate (TBMA) 10 parts by mass, acrylic acid 2- 80 parts by mass of ethylhexyl (EHA), 5 parts by mass of styrene (ST), 1 part by mass of allyl methacrylate (AMA), 2 parts by mass of acrylic acid (AA) and 2 parts by mass of methyl methacrylate (MMA) and 50 parts by mass of water After sequentially charging, the mixture was stirred to obtain an emulsion. 10% by weight of the prepared emulsion was put into the 7L separable flask and stirred for 30 minutes. Then, a 5% aqueous solution containing 0.5 parts by mass of potassium persulfate as an initiator and hydrosulfite as an oxygen scavenger were used. A 1% aqueous solution containing 0.02 part by mass of sodium was added and reacted at 75 ° C. for 1 hour. Thereafter, the remaining 90% by weight of the emulsified liquid was dropped over 5 hours, and further reacted for 2 hours, and then cooled to 40 ° C. to stop the reaction. Monomer conversion was 99.8%. Subsequently, the aqueous suspension containing 0.2% by weight of 2-methyl-4-isothiazolin-3-one as a preservative was adjusted to pH 7.5 with a 2.5N aqueous sodium hydroxide solution as an antifoaming agent. “SN deformer 388N” (trade name, manufactured by San Nopco Co., Ltd.) was added to obtain an aqueous dispersion containing 40% by mass of the polymer (A10) particles. Various evaluations were performed in the same manner as in Synthesis Example A1 using the aqueous dispersion containing the obtained polymer (A10). The evaluation results are shown in Table 1.

5.1.7. Synthesis Example 11 to Synthesis Example 13
In Synthesis Example A10, a polymer having a solid content concentration of 40% by mass (polymer (A11)) was prepared in the same manner as in Synthesis Example A10, except that the types and amounts of the respective monomers were as shown in Table 1. An aqueous dispersion containing particles consisting of (A13) was prepared, and various evaluations were performed in the same manner as in Synthesis Example A1. The evaluation results are shown in Table 1.
5.1.8. Synthesis Example 17
After sufficiently substituting the inside of the 7 L separable flask with nitrogen, 100 parts by mass of polymer (A7) obtained in Synthesis Example 7 (in terms of solid content), 20 parts by mass of acrylonitrile, sodium dodecylbenzenesulfonate 0.5 After charging a mass part, it heated up at 75 degreeC. 1 part by mass of cumene hydroperoxide as an initiator and 1 part by mass of L-ascorbic acid as an initiator were added, reacted at 75 ° C. for 4 hours, then heated to 85 ° C. and further reacted for 2 hours. The polymerization conversion rate determined from the solid content concentration was about 99%. Thereafter, the pH was adjusted to 8.5 with sodium hydroxide, and ion-exchanged water was added to prepare an aqueous dispersion containing particles composed of a polymer (A17) having a solid concentration of 40% by mass. Various evaluations were performed in the same manner as in Synthesis Example A1 using the obtained aqueous dispersion containing the polymer (A17). The evaluation results are shown in Table 2.
5.1.9. Synthesis Examples 18 to 27
In Synthesis Example 17, the type and amount of seed particles and the type and amount of each monomer were as shown in Table 2, respectively. An aqueous dispersion containing particles composed of a polymer (polymers (A18) to (A27)) was prepared, and various evaluations were performed in the same manner as in Synthesis Example A1. The evaluation results are shown in Table 2.
5.2. Synthesis of Resin (B) 5.2.1. Synthesis Example 14 to Synthesis Example 16
Resin (resin (B1) to (resin (B1) to (solid resin)) having a solid content concentration of 40% by mass was the same as in Synthesis Example A2 except that the type and amount of each monomer were as shown in Table 1 in Synthesis Example A2. An aqueous dispersion containing particles consisting of B3)) was prepared, and various evaluations were performed in the same manner as in Synthesis Example A1. The evaluation results are shown in Table 1.

Abbreviations of monomers in Table 1 and Table 2 have the following meanings, respectively. “−” In the monomer column indicates that the monomer was not used or the evaluation value of the monomer was not observed.
<Compound (a1)>
CHMA: cyclohexyl methacrylate IMA: isobornyl methacrylate MAdMA: 2- (2-methyladamantyl methacrylate)
CMA: 3-cholesteryl methacrylate <compound (a2)>
AN: Acrylonitrile MAN: Methacrylonitrile <Compound (a3)>
AA: Acrylic acid MAA: Methacrylic acid TA: Itaconic acid <Compound (a4)>
VdDF: vinylidene fluoride HFP: propylene hexafluoride TFE: ethylene tetrafluoride 2VE: 1,1,2,2-tetrafluoro-1,2-bis ((trifluorovinyl) oxy) ethane TFEMA: methacrylate 2 2,2-trifluoroethyl TFEA: 2,2,2-trifluoroethyl acrylate HFIPA: 1,1,1,3,3,3-hexafluoroisopropyl acrylate <compound (a5)>
MMA: Methyl methacrylate EHA: 2-ethylhexyl acrylate BA: n-butyl acrylate TBMA: t-butyl acrylate EA: ethyl acrylate HEMA: 2-hydroxyethyl methacrylate <compound (a6)>
BD: 1,3-butadiene ST: Styrene <Compound (a7)>
DVB: divinylbenzene TMPTMA: trimethylolpropane trimethacrylate EDMA: ethylene glycol dimethacrylate AMA: allyl methacrylate 5.3. Preparation of Binder Composition (G1) for Electricity Storage Device An alicyclic saturated hydrocarbon resin (trade name “M-100” manufactured by Arakawa Chemical Industries, Ltd.) is used as the resin (B), and water is used as a medium. An aqueous dispersion of resin (B4) having a solid content concentration of 50% by mass was prepared by the high-pressure emulsification method described in No. 1. The polymerization average molecular weight of the resin (B4) was measured in the same manner as in Synthesis Example 1. The evaluation results are shown in Table 3.

  Into a 7-liter separable flask, 80 parts by mass of the polymer (A1) obtained in the above synthesis example and 20 parts by mass of the aqueous dispersion of the resin (B4) were charged in terms of solid content, and water was added. The solid content was adjusted to 40% and sufficiently stirred for 30 minutes to obtain a binder composition (G1).

  Except that the type and amount of the polymer (A) and the type and amount of the resin (B) were as shown in Table 3, the same as in “5.3. Preparation of binder composition for electricity storage device” above. Thus, a binder composition (polymers (G2) to (G17)) having a solid content concentration of 40% by mass was obtained. The molecular weight of the used resin (B) was evaluated in the same manner as the resin (B1). The evaluation results are shown in Table 3.

5.4. Example 1 (Application of binder composition to protective film)
5.4.1. Production and evaluation of electricity storage devices <Formation of protective film (manufacture of separator with protective film)>
The binder composition (G1) obtained above was applied to one side of a separator (trade name “Celguard # 2400”, manufactured by Celgard) made of a polypropylene porous film on one side using a gravure coating machine, and 80 ° C. After drying for 10 minutes, the binder composition (G1) was applied to the uncoated surface in the same manner to form a protective film on both surfaces of the separator, thereby manufacturing a separator with a protective film. The thickness of the formed protective film was 2 μm on each side (4 μm in total on both sides).

5.4.2. Production of positive electrode <Preparation of positive electrode active material>
Commercially available lithium iron phosphate (LiFePO ₄ ) was pulverized in an agate mortar and classified using a sieve to prepare active material particles having a particle diameter (D50 value) of 0.5 μm.
<Preparation of slurry for positive electrode>
A biaxial planetary mixer (product name “TK Hibismix 2P-03” manufactured by PRIMIX Co., Ltd.), 4 parts by mass of polyvinylidene fluoride (in terms of solid content), 100 parts by mass of the active material particles, 5 parts by mass of acetylene black, and 68 parts by mass of N-methylpyrrolidone was added and stirred at 60 rpm for 1 hour. Further, 32 parts by mass of N-methylpyrrolidone was added and stirred for 1 hour to obtain a paste. The obtained paste was stirred at 200 rpm for 2 minutes, 1800 rpm for 5 minutes, and further under vacuum (5.0 × 10 ³ ) using a stirring defoaming machine (trade name “Awatori Netaro”, manufactured by Shinky Corporation). The slurry for positive electrode was prepared by stirring and mixing at 1800 rpm for 1.5 minutes at Pa).
<Preparation of electrode for positive electrode>
The 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 100 μm, and dried at 120 ° C. for 20 minutes. Then, the positive electrode with the positive electrode active material layer formed on the surface of the current collector was obtained by pressing with a roll press so that the density of the film (active material layer) was 2.0 g / cm ³ .

5.4.3. Production of negative electrode <Preparation of slurry for negative electrode>
A biaxial planetary mixer “TK Hibismix 2P-03” was charged with 4 parts by mass of polyvinylidene fluoride (PVDF), 100 parts by mass of graphite as a negative electrode active material, and 80 parts by mass of N-methylpyrrolidone (NMP). Stirring was performed at 60 rpm for 1 hour. 20 parts of NMP is added to the mixture after stirring, and the mixture is stirred and mixed for 2 minutes at 200 rpm, 5 minutes at 1,800 rpm, and 1.5 minutes at 1,800 rpm under vacuum using a stirring defoaming machine “Awatori Netaro” Thus, a slurry for negative electrode was prepared.
<Preparation of electrode for negative electrode>
The negative electrode slurry was uniformly applied to the surface of a current collector made of copper foil by a doctor blade method so that the film thickness after drying was 150 μm, and dried at 120 ° C. for 20 minutes. Then, the negative electrode was manufactured by pressing using a roll press so that the density of a film | membrane may be 1.5 g / cm < ³ >.
(4) 5.4.4. Adhesiveness between protective film and electrode From the negative electrode, separator with protective film, and positive electrode manufactured above, test pieces each having a width of 2 cm and a length of 5 cm were cut out, and the negative electrode active material layer and the positive electrode active material layer were each provided with a protective film. A negative electrode / a separator with a protective film / a positive electrode was laminated so as to face the separator. The obtained laminate was impregnated with a solvent of ethylene carbonate / ethyl methyl carbonate = 1/1 (mass ratio), and sandwiched between polyester films (Lumirror S10, 250 μm thickness, manufactured by Toray Industries, Inc.), 100 ° C. × 10 minutes, 0 Heated and pressurized at 1 MPa. Then, before the solvent dried, the negative electrode and the positive electrode were peeled off from the separator with the protective film, and evaluated as follows. The evaluation results are shown in Table 3.
A: When both the negative electrode and the positive electrode are peeled off, there is resistance, and a part or all of the active material layer is transferred by being adhered to the protective film.
○: Although there is resistance when both the negative electrode and the positive electrode are peeled off, it is determined that the active material layer is not transferred to the protective film.
X: When either the negative electrode or the positive electrode is peeled off, there is no resistance, and if it is already peeled off, it is judged as defective.

5.4.5. Assembly of Lithium Ion Battery Cell A bipolar coin cell (Hosen Co., Ltd.) obtained by punching and molding the negative electrode produced above to a diameter of 16.16 mm in an Ar-substituted glove box with a dew point of −80 ° C. or lower. And product name “HS flat cell”). Next, the separator with the protective film obtained in “5.3.3 Production of protective film” punched out to a diameter of 24 mm was placed, and after injecting 500 μL of the electrolyte solution so that air did not enter, The positive electrode with a protective film manufactured in the above is punched and molded to a diameter of 15.95 mm and placed so that the separator and the protective film formed on the positive electrode face each other, and the outer body of the bipolar coin cell is closed with a screw. The lithium ion battery cell (electric storage device) was assembled by sealing. The electrolytic solution used here is a solution obtained by dissolving LiPF ₆ at a concentration of 1 mol / L in a solvent of ethylene carbonate / ethyl methyl carbonate = 1/1 (mass ratio).

5.4.6. Measurement of remaining capacity rate and resistance increase rate The battery cell produced above was placed in a thermostatic bath at 25 ° C., charging was started at a constant current (0.2 C), and when the voltage reached 4.1 V, it was continuously determined. Charging was continued at a voltage (4.1 V), and charging was completed (cut off) when the current value reached 0.01C. 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) was 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). When the voltage reaches 4.1 V, the constant voltage (4.1 V) continues. 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 remaining capacity rate obtained by substituting the above measured values into the following formula (7) is 98%, and the resistance increase rate obtained by substituting the above measured values into the following formula (8) is 40%. there were.

Remaining capacity ratio (%) = (C2 / C1) × 100 (7)
Resistance increase rate (%) = (EISb / EISa) × 100 (8)
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.

In the above measurement conditions, “1C” indicates a current value at which discharge is completed in one hour after constant current discharge of a cell having a certain electric capacity. For example, “0.1 C” is a current value at which discharge is completed over 10 hours, and “10 C” is a current value at which discharge is completed over 0.1 hours.
5.4.7. Evaluation of shutdown characteristics and 130 ° C. resistance maintenance ratio 1M LiPF ₆ Ethylene carbonate / diethyl carbonate (3/7 weight ratio) (manufactured by Kishida Chemical Co., Ltd.) and protection obtained in the above “5.3.3 Production of protective film” A unit in which a separator with a film was brought into contact with and interposed between two aluminum (Niraco) current collectors was prepared and loaded into a flat cell (Takumi Giken, flat cell) to prepare an evaluation cell.

  The evaluation cell was placed in a hot stove, heated from a temperature of 30 ° C. to 130 ° C. at a rate of 5 ° C./min, held at 130 ° C. for 20 minutes, and then an LCR meter (manufactured by Hioki Electric Co., Ltd. The resistance at 1 Hz measured by LCR HiTESTER ”was 130Ω. If the internal resistance at 130 ° C. is 100Ω or more, it is judged that the shutdown characteristic is good, and if it is less than 100Ω, it is judged as defective and “x” is shown in Table 3.

5.4.8. Examples 2-10, Comparative Examples 1-6
A binder composition G for an electricity storage device was prepared in the same manner as in Example 1 except that the types and amounts of the polymer and the additive resin were as shown in Table 3, respectively. Various evaluations were performed in the same manner as described above. The evaluation results are shown in Table 3.
5.4.9. Example 11
In Example 1 above, NMP 92 parts by mass of the binder composition for an electricity storage device, 8 parts by mass of PVdF instead of the polymer (A1), and 2 parts by mass of additive resin Quintone 1500 were charged in terms of solid content, respectively, and 60 at 80 ° C. Various evaluations were performed in the same manner as in Example 1 except that adjustment was performed by sufficiently stirring for one minute. The evaluation results are shown in Table 3.

5.5. Example 12 (Application of binder composition to heat-resistant protective film)
5.5.1. Preparation of slurry for protective film To 500 parts by mass of water, 100 parts by mass of magnesium oxide as a filler (manufactured by Tateho Chemical Industry Co., Ltd., trade name “PUREMAG (R) FNM-G”, number average particle size 0.50 μm),
An amount corresponding to 10 parts by mass of the binder composition for electricity storage device (G1) obtained in Example 1 above, and 1 part by mass of a product name “CMC1120” manufactured by Daicel Corporation as a thickener. The slurry for protective film was prepared by carrying out mixing and dispersion treatment using a thin film swirl type high-speed mixer “TK Fillmix (R) 56-50” manufactured by Primix Co., Ltd.
5.5.2. Production and evaluation of electricity storage device (1) <Production of positive electrode with protective film>
After producing the positive electrode in the same manner as in “Manufacture of positive electrode” in Example 1, the slurry for the protective film prepared above was applied to the surface of the active material layer of the positive electrode by the die coating method, and then at 120 ° C. for 5 minutes. By drying, a protective film with a thickness of 3 μm was formed on the surface of the positive electrode active material layer to obtain a positive electrode with a protective film.

5.5.3. Adhesiveness between separator and electrode with protective film The negative electrode manufactured in Example 1 and the positive electrode manufactured above were used. The separator was manufactured by Celgard, using the trade name “Cell Guard # 2400”, and each test was 2 cm wide × 5 cm long. The piece was cut out, and the negative electrode / separator / positive electrode with a protective film was laminated so that the negative electrode active material layer and the positive electrode active material layer were respectively opposed to the separator. The obtained laminate was impregnated with a solvent of ethylene carbonate / ethyl methyl carbonate = 1/1 (mass ratio), and sandwiched between polyester films (Lumirror S10, 250 μm thickness, manufactured by Toray Industries, Inc.), 100 ° C. × 10 minutes, 0 Heated and pressurized at 1 MPa. Then, before the solvent dried, the positive electrode was peeled off from the separator with a protective film, and evaluated as follows. The evaluation results are shown in Table 4.
A: When the positive electrode is peeled off, there is resistance, and when a part or the whole of the active material layer is adhered and transferred to the protective film, it is judged to be particularly good.
◯: Although there is resistance when the positive electrode is peeled off, it is judged good when the active material layer is not transferred to the protective film.
X: When there is no resistance when the positive electrode is peeled off and it has already been peeled off, it is judged as defective.

5.5.4. Assembly and Evaluation of Lithium Ion Secondary Battery Cell Using the positive electrode with the protective film manufactured above as the positive electrode, the product name “Cell Guard # 2400” (without the protective film) manufactured by Celgard as the separator is punched into a diameter of 24 mm. A lithium ion secondary battery cell (electric storage device) was produced in the same manner as in Example 1 except that the obtained one was used, and the remaining capacity rate and the resistance increase rate were evaluated. In addition, when placing the positive electrode with a protective film in a coin cell, it was set as the direction in which a protective film faces a lower side (separator side). The evaluation results are shown in Table 4.

5.5.5. Examples 13-22 and Comparative Examples 7-12
In Example 12, the type and amount of filler (E) used in “Preparation of slurry for protective film” and the type and amount of binder composition for electricity storage device (G) are as shown in Table 4, respectively. A slurry for protective film was prepared in the same manner as in Example 12, and a lithium ion secondary battery cell (electric storage device) was produced and evaluated using the slurry for protective film. The evaluation results are shown in Table 4, respectively.

Example 23 <Application of Binder Composition to Electrode>
5.6.1. Production and evaluation of positive electrode (1) <Preparation of slurry for positive electrode>
A biaxial planetary mixer (product name "TK Hibismix 2P-03" manufactured by PRIMIX Co., Ltd.) and a thickener (product name "CMC1120", manufactured by Daicel Corporation) 2 parts by mass (Solid content conversion value), electrode active material (commercially available lithium iron phosphate (LiFePO ₄ ) was pulverized in an agate mortar and classified using a sieve, and the particle diameter (D50 value) was 0.5 μm. 1) 100 parts by mass, 3 parts by mass of acetylene black and 15 parts by mass of water were added as a conductivity-imparting agent, and the mixture was stirred at 90 rpm for 1 hour. Next, the power storage device binder composition (G1) obtained in Example 1 above is added so that the proportion of the solid content in the composition is 4 parts by mass, and further 85 parts by mass of water. After adding, the mixture was stirred for 1 hour to obtain a paste. After adding water to the obtained paste to adjust the solid content concentration to 40% by mass, the mixture was stirred at 200 rpm for 2 minutes at 200 rpm using a defoaming machine (manufactured by Shinky Co., Ltd., trade name “Awatori Nertaro”). The positive electrode slurry was prepared by stirring and mixing at 1,800 rpm for 5 minutes and further under reduced pressure (about 5 × 10 ³ Pa) at 1,800 rpm for 1.5 minutes.

<Production of positive electrode>
The positive electrode slurry prepared above was uniformly applied to the surface of a current collector made of an aluminum foil having a thickness of 30 μm by the doctor blade method so that the film thickness after drying was 100 μm, and dried at 120 ° C. for 20 minutes. . Thereafter, the film (electrode active material layer) is pressed by a roll press so that the density is 1.9 g / cm ³ , and further vacuum-dried at 150 ° C. for 4 hours under a reduced pressure of 75 Pa of absolute pressure. Got.

5.6.2. Adhesiveness between Protective Film and Electrode A negative electrode / separator / positive electrode was laminated in the same manner as in Example 12 except that the positive electrode produced above was used. The obtained laminate was impregnated with a solvent of ethylene carbonate / ethyl methyl carbonate = 1/1 (mass ratio), and sandwiched between polyester films (Lumirror S10, 250 μm thickness, manufactured by Toray Industries, Inc.), 100 ° C. × 10 minutes, 0 Heated and pressurized at 1 MPa. Then, before the solvent dried, the positive electrode was peeled off from the separator and evaluated as follows. The evaluation results are shown in Table 5.
A: When the positive electrode is peeled off, there is resistance, and when a part or the whole of the active material layer is adhered and transferred to the separator, it is judged to be particularly good.
○: Although there is resistance when the positive electrode is peeled off, it is judged as good when the active material layer is not transferred to the separator.
X: When there is no resistance when the positive electrode is peeled off and it has already been peeled off, it is judged as defective.
(5) 5.6.3. Assembly of Lithium Ion Secondary Battery Cell A battery cell was assembled and evaluated in the same manner as in Example 12 except that the positive electrode manufactured above was used. The evaluation results are shown in Table 5.
5.6.4. Examples 24-32 and Comparative Examples 13-17
In Example 23 above, a protective film was prepared in the same manner as in Example 23 except that the type of the binder composition for electricity storage device (G) used in “Preparation of slurry for positive electrode” was as shown in Table 5. A slurry for a battery was prepared, and a lithium ion secondary battery cell (power storage device) was produced and evaluated using the slurry for a protective film. The evaluation results are shown in Table 5, respectively.
5.6.4. Example 33
In Example 23, the particle diameter (D50 value) obtained by pulverizing an electrode active material (commercially available lithium iron phosphate (LiFePO ₄ ) in an agate mortar and classifying with a sieve in the positive electrode production was 0. 0.5 μm) 100 parts by mass, 3 parts by mass of acetylene black as a conductivity-imparting agent, and 15 parts by mass of NMP, and the binder composition for an electricity storage device (G11) obtained in Example 11 above was added to the composition. Evaluation was made in the same manner as in Example 22 except that the solid content was 4 parts by mass and the solid content concentration of the obtained paste was adjusted to 40% by mass. The evaluation results are shown in Table 5.
Examples 34-44
In Example 23, the type of binder composition (G) for an electricity storage device used in “Preparation of slurry for positive electrode” was as described in Table 6, respectively. A slurry was prepared, and a lithium ion secondary battery cell (electric storage device) was produced and evaluated using the positive electrode slurry. The evaluation results are shown in Table 6, respectively.

  As is apparent from Table 3 above, the separator having the protective film according to the present invention shown in Examples 1 to 11 exhibits very good adhesiveness with the electrode, and an electricity storage device (lithium ion battery) including these separators Was excellent in the remaining capacity after the durability test and the suppression of the resistance rise. In addition, the separators of Examples 5 to 7 showed good adhesion to the electrode and excellent battery characteristics, and an increase in resistance at 130 ° C. was confirmed, and the effect on ensuring the safety during thermal runaway of the battery was shown. . On the other hand, in Comparative Examples 1-6, the separator with favorable adhesiveness with an electrode was not obtained. This is probably because the protective film formed only of the polymers (A) of Comparative Examples 1 and 2 has low wettability with respect to the separator and sufficient adhesiveness was not expressed. In Comparative Example 3, since the protective film formed only of the resin (B) has good wettability with respect to the separator, it is considered that sufficient adhesiveness was not obtained because the binder component responsible for adhesion was not included. . In Comparative Examples 4 and 5, when the rosin ester type was used for the resin (B), the resin (B) component was dissolved in the electrolytic solution, and thus the protective film was considered to have dropped off.

  As is apparent from Table 4 above, the electrodes having the protective film according to the present invention shown in Examples 12 to 22 exhibit very good adhesiveness to the separator, and an electricity storage device (lithium ion battery) including these electrodes Showed good battery characteristics with good remaining capacity after endurance test. On the other hand, in Comparative Examples 6 to 10, a protective film having good adhesion to the separator was not obtained.

  As is clear from Tables 5 and 6 above, the electrodes according to the present invention shown in Examples 23 to 44 showed very good adhesiveness with the separator and showed good battery characteristics. On the other hand, in Comparative Examples 11-15, the protective film with favorable adhesiveness with a separator was not obtained.

  The present invention is not limited to the above embodiment, and various modifications can be made. The present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same objects and effects). The present invention also includes a configuration in which a non-essential part of the configuration described in the above embodiment is replaced with another configuration. Furthermore, the present invention includes a configuration that achieves the same effects as the configuration described in the above embodiment or a configuration that can achieve the same object. Furthermore, the present invention includes a configuration obtained by adding a known technique to the configuration described in the above embodiment.

  1, 2, 3 ... Electric storage device 10, 110, 210 ... Positive electrode, 12, 112, 212 ... Positive electrode current collector, 14, 114, 214 ... Positive electrode active material layer, 20, 120, 220 ... Negative electrode, 22, 122 222, negative electrode current collector, 24, 124, 224 ... negative electrode active material layer, 30, 130, 230 ... protective film, 40, 140, 240 ... electrolyte, 150, 250 ... separator.

Claims (12)

A power storage device comprising a polymer (A) having a polymerization average molecular weight (Mw) of 10,000 or more and a resin (B) containing a repeating unit having an alicyclic hydrocarbon group and having a polymerization average molecular weight (Mw) of less than 10,000. Binder composition.   The value of Mb / Ma is 0.1-20, when the content of the polymer (A) is Ma parts by mass and the content of the resin (B) is Mb parts by mass. Binder composition for electricity storage device. The electricity storage device according to claim 1 or 2, wherein the polymer (A) is a polymer including a repeating unit derived from an unsaturated carboxylic acid ester and a repeating unit derived from an unsaturated carboxylic acid. Binder composition.   The binder composition for an electricity storage device according to claim 3, wherein the polymer (A) is a polymer further comprising a repeating unit derived from a conjugated diene compound and a repeating unit derived from an aromatic vinyl compound.   When the repeating unit derived from the unsaturated carboxylic acid ester includes a repeating unit having an alicyclic hydrocarbon group, and the total repeating unit of the polymer (A) is 100% by mass, the alicyclic hydrocarbon group The binder composition for electrical storage devices of Claim 3 or Claim 4 whose repeating unit which has is 0.1-20 mass%. The binder composition for an electricity storage device according to any one of claims 1 to 5, wherein the polymer (A) is a fluorine-containing polymer containing a repeating unit derived from a fluorine-containing ethylene monomer. object.   The binder composition for an electricity storage device according to any one of claims 1 to 6, wherein the resin (B) contains 50% by mass or more of a repeating unit having an alicyclic hydrocarbon group.   The slurry for electrodes of an electrical storage device containing the binder composition for electrical storage devices as described in any one of Claims 1-7, and an active material.   An active material layer produced using the slurry for electrode of an electricity storage device according to claim 8.   The slurry for protective films of an electrical storage device containing the binder composition for electrical storage devices as described in any one of Claims 1-7, and a filler.   The separator produced using the slurry for protective films of the electrical storage device of Claim 10.   An electricity storage device comprising at least one of the electrode for an electricity storage device according to claim 9 and the separator according to claim 11.