JP2015118908A - Binder composition for electricity storage device, slurry for electricity storage device, electricity storage device electrode, separator, and electricity storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a binder composition for an electricity storage device, capable of forming a layer that is excellent in adhesion with a collector or a separator and also capable of producing an electricity storage device that is excellent in charge/discharge characteristics.SOLUTION: A binder composition for an electricity storage device according to the present invention contains: a water-soluble polymer (A); at least one compound (B) selected from the group consisting of unsaturated carboxylic acid, unsaturated amide and a salt thereof; and a liquid medium (C). A ratio of repeating units that are contained in 100 pts.mass of the water-soluble polymer (A) and derived from (meth)acrylamide is 40-100 pts.mass.

Description

  The present invention relates to a binder composition for an electricity storage device, a slurry for an electricity storage device containing the binder composition, an electricity storage device electrode comprising a layer prepared by applying and drying the slurry, and applying and drying the slurry. The present invention relates to a separator provided with a layer formed on the surface, and an electricity storage device including at least one of the electrode and the separator.

  A positive electrode and a negative electrode (hereinafter, also referred to as “electrode”) used in an electricity storage device are formed by applying a mixture of an active material and a binder to a surface of a current collector and drying the active material layer on the surface of the current collector. (See, for example, Patent Document 1). In recent years, a technique has also been proposed in which a mixture of a filler and a binder is applied to the separator surface and dried to form a protective film that can withstand dendrites on the separator surface. Thus, in the field of power storage devices, it is common to provide a layer containing an active material or filler on the surface of an electrode or a separator (see, for example, Patent Document 2).

  Properties required for such a binder include bonding between active material particles and fillers, and a composition layer for an electrode containing active material particles (hereinafter also referred to as “active material layer”) and a current collector. Adhesive ability, adhesive ability between a protective film containing a filler and a separator or an active material layer, abrasion resistance in a process of winding an electrode or separator provided with these layers, an active material layer applied by subsequent cutting, etc. There is a powder fall resistance that does not generate fine powder from the protective film. In addition, about the binding ability of the above active material particles and fillers, the binding ability between the active material particles and the current collector, the adhesion ability between the protective film containing the filler and the separator and the active material layer, and the resistance to dusting of these From experience, it is clear that the performance is almost proportional. Therefore, in the present specification, these may be collectively expressed below using the term “adhesion”.

  As an electrode binder, for example, Patent Document 3 and Patent Document 4 disclose a technique for achieving both oxidation resistance and adhesion of an electrode binder by using a rubber polymer and another polymer in combination. Has been proposed. Patent Document 5 discloses a technique for improving adhesion by dissolving polyvinylidene fluoride in a specific organic solvent, applying it onto the current collector surface, and then removing the solvent at a low temperature. Has been proposed.

  As a protective film binder, for example, Patent Document 6 examines a technique for improving battery characteristics by forming a porous layer containing a resin binder containing polyamide, polyimide, and polyamideimide on a porous separator substrate. Has been. Patent Document 7 discusses a technique for improving battery characteristics by forming a porous protective film containing a binder containing a fluorine resin and a rubber resin on at least one surface of a positive electrode and a negative electrode. ing.

JP 2013-30449 A JP 2011-5867 A JP 2011-3529 A JP 2012-151108 A JP 2010-55847 A International Publication No. 2009/041395 JP 2009-54455 A

  However, according to the techniques described in Patent Document 3 and Patent Document 4 in which a rubber-based polymer and another polymer are used in combination, although the adhesion is improved, the oxidation resistance of the organic polymer is greatly impaired. An electricity storage device manufactured using this has a problem that charge and discharge characteristics are irreversibly deteriorated by repeated charge and discharge. Moreover, in the technique described in Patent Document 4, since the acrylic copolymer dispersed in water is used as a binder component, the binder component is not uniform in the coating film depending on the dispersion state of the acrylic copolymer. In some cases, the adhesion is improved but locally insufficient. On the other hand, according to the technique described in Patent Document 5 that uses only a fluorine-containing organic polymer as a binder component, the adhesion is still insufficient.

  On the other hand, according to the materials as described in Patent Document 6 and Patent Document 7, although a short circuit caused by dendrite generated along with charge / discharge can be suppressed by forming a protective film on the separator or electrode surface, Since the permeability and liquid retention of the electrolytic solution are lowered, lithium ions are prevented from adsorbing and desorbing to the active material. As a result, there is a problem that the internal resistance of the electricity storage device increases and the charge / discharge characteristics are deteriorated.

  Thus, in the prior art, a technique for improving the charge / discharge characteristics by improving the adhesion by using an emulsion in which a polymer as a binder component is dispersed in water has been proposed. However, a technique using only a water-soluble polymer as a binder component has not been studied much. If only a water-soluble polymer can be used as the binder component, non-uniformity of the binder component in the coating film is eliminated, and further improvement in adhesion can be expected.

  On the other hand, conventional electrode binders and protective film binders are only evaluated for their superiority and inferiority by paying attention to the characteristics of electricity storage devices, and there is sufficient study on storage stability, which is important for practical use. Not done. Emulsion-type binders in which polymer particles are dispersed in water, as in the prior art, always have an issue of improving the dispersion stability of polymer particles, and ensuring storage stability is particularly important for practical use. It becomes.

  Accordingly, some embodiments according to the present invention can form a layer having excellent adhesion to a current collector or a separator by solving at least a part of the above-described problem, and also have an electric storage device having excellent charge / discharge characteristics. The binder composition for electrical storage devices which can manufacture is provided. In addition to these, some embodiments according to the present invention provide a binder composition for an electricity storage device that further improves storage stability.

  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 water-soluble polymer (A);
At least one compound (B) selected from the group consisting of unsaturated carboxylic acids, unsaturated amides, and salts thereof;
A liquid medium (C);
Containing
The ratio of the repeating unit derived from (meth) acrylamide contained in 100 parts by mass of the water-soluble polymer (A) is 40 to 100 parts by mass.

[Application Example 2]
In the binder composition for an electricity storage device of Application Example 1,
The said compound (B) can be contained 0.01-0.5 mass part with respect to 100 mass parts of said water-soluble polymers (A).

[Application Example 3]
In the binder composition for an electricity storage device of Application Example 1 or Application Example 2,
The water-soluble polymer (A) is a repeating unit derived from at least one selected from the group consisting of an acid having a polymerizable unsaturated double bond, an unsaturated carboxylic acid ester, and an α, β-unsaturated nitrile compound. Can further be included.

[Application Example 4]
In the binder composition for an electricity storage device of Application Example 3,
The acid having a polymerizable unsaturated double bond may be at least one selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, vinyl sulfonic acid, allyl sulfonic acid, and methallyl sulfonic acid.

[Application Example 5]
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 of the application examples 1 to 4, and an active material.

[Application Example 6]
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 4, and a filler.

[Application Example 7]
In the slurry for the electricity storage device of Application Example 6,
The filler may be at least one particle selected from the group consisting of silica, titanium oxide, aluminum oxide, zirconium oxide, and magnesium oxide.

[Application Example 8]
One aspect of the electricity storage device electrode according to the present invention is:
It is characterized by comprising: a current collector; and a layer formed by applying and drying the electricity storage device slurry of Application Example 5 on the surface of the current collector.

[Application Example 9]
One aspect of the electricity storage device electrode according to the present invention is:
A current collector, and an active material layer formed on the surface of the current collector,
It is further characterized by further comprising a layer formed by applying and drying the electricity storage device slurry of Application Example 6 or Application Example 7 on the surface of the active material layer.

[Application Example 10]
One aspect of the separator according to the present invention is:
A layer formed by applying and drying the slurry for an electricity storage device of Application Example 6 or Application Example 7 is provided on the surface.

[Application Example 11]
One aspect of the electricity storage device according to the present invention is:
It is characterized by including at least one of the electricity storage device electrode of Application Example 8 or Application Example 9 and the separator described in Application Example 10.

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

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

  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 the present specification, “(meth) acrylic acid” is a concept encompassing both “acrylic acid” and “methacrylic acid”.

1. Binder composition for electricity storage device The binder composition for electricity storage device according to the present embodiment is at least selected from the group consisting of a water-soluble polymer (A), an unsaturated carboxylic acid, an unsaturated amide, and a salt thereof. A repeating unit derived from (meth) acrylamide, containing one kind of compound (B) and a liquid medium (C), wherein the total repeating unit of the water-soluble polymer (A) is 100 parts by mass. The content ratio of is 40 to 100 parts by mass.

  The water-soluble polymer (A) contained in the binder composition for an electricity storage device according to the present embodiment has not only a function as a thickener typified by conventional carboxymethyl cellulose but also a binding ability between active material particles. In addition, it also has a function as a binder for improving the binding ability between the active material particles and the current collector and the resistance to powder falling. Therefore, in the binder composition for an electricity storage device according to the present embodiment, it is not necessary to use a water-insoluble polymer (organic particle) having a function as a binder as described in JP2012-151108A. Excellent in terms.

  The “water-soluble polymer” in the present invention refers to a polymer having a solubility in 1 g of water at 1 atm and 23 ° C. of 0.01 g or more. The “water-insoluble polymer” in the present invention refers to a polymer having a solubility in 1 g of water at 1 atm and 23 ° C. of less than 0.01 g.

The binder composition for an electricity storage device according to the present embodiment can be broadly classified into two applications. As the first application, there is an application for producing an electricity storage device electrode. Specifically, it can be used as a binder for producing an active material layer formed on the surface of a current collector. As a second application, there is an application for producing a protective film on the surface of an electrode or a separator for suppressing a short circuit caused by a dendrite generated along with charge and discharge. Hereafter, each component contained in the binder composition for electrical storage devices which concerns on this Embodiment is demonstrated in detail.

1.1. Water-soluble polymer (A)
The binder composition for an electricity storage device according to the present embodiment includes a water-soluble polymer (A) containing a repeating unit derived from (meth) acrylamide. In addition to the repeating unit derived from (meth) acrylamide, the water-soluble polymer (A) may contain a repeating unit derived from another monomer copolymerizable therewith. Examples of the other monomer include an acid having a polymerizable unsaturated double bond, an unsaturated carboxylic acid ester, an α, β-unsaturated nitrile compound, a conjugated diene compound, and an aromatic vinyl compound.

  Hereinafter, the repeating unit constituting the water-soluble polymer (A), the molecular weight of the water-soluble polymer (A), the physical properties, and the production method will be described in this order.

1.1.1. The repeating unit derived from (meth) acrylamide The ratio of the repeating unit derived from (meth) acrylamide contained in 100 parts by mass of the water-soluble polymer (A) is 40 to 100 parts by mass, and 45 to 95 parts by mass. It is preferable that it is 50 to 85 parts by mass. By containing the repeating unit derived from (meth) acrylamide in the above range, the dispersibility of the active material and filler becomes good, and it becomes possible to produce a uniform active material layer and a protective film. Shows excellent charge / discharge characteristics. Furthermore, by containing a repeating unit derived from (meth) acrylamide in the above range, the oxidation resistance of the polymer becomes good, and therefore, deterioration at high voltage is suppressed, and good charge / discharge durability characteristics are exhibited.

（式（１）中、Ｒ^１は水素原子またはメチル基を表す。） (Meth) acrylamide in the present invention is a generic name for compounds having a (meth) acrylamide skeleton represented by the following general formula (1).

(In formula (1), R ¹ represents a hydrogen atom or a methyl group.)

  Examples of such (meth) acrylamide include acrylamide, methacrylamide, N-isopropylacrylamide, N, N-dimethylacrylamide, N, N-dimethylmethacrylamide, N, N-diethylacrylamide, and N, N-diethylmethacrylate. Examples include amide, N, N-dimethylaminopropyl acrylamide, N, N-dimethylaminopropyl methacrylamide, N-methylol methacrylamide, N-methylol acrylamide, diacetone acrylamide, maleic acid amide, and acrylamide t-butyl sulfonic acid. . These (meth) acrylamides may be used alone or in combination of two or more.

1.1.2. Repeating unit derived from an acid having a polymerizable unsaturated double bond The water-soluble polymer (A) is an acid having a polymerizable unsaturated double bond (excluding those corresponding to the above (meth) acrylamide). It may have repeating units derived from it. When the water-soluble polymer (A) has a repeating unit derived from an acid having a polymerizable unsaturated double bond, the polymerizable unsaturated double bond contained in 100 parts by mass of the water-soluble polymer (A) The ratio of the repeating unit derived from the acid it has is preferably 0 to 30 parts by mass, and more preferably 5 to 25 parts by mass. The water-soluble polymer (A) was prepared using the binder composition for an electricity storage device according to the present embodiment by containing a repeating unit derived from an acid having a polymerizable unsaturated double bond in the above range. The stability of the slurry for the electricity storage device is improved.

  As the acid having a polymerizable unsaturated double bond, an unsaturated carboxylic acid or an unsaturated sulfonic acid can be preferably used. Specific examples of the acid having a polymerizable unsaturated double bond include, for example, acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid and other unsaturated carboxylic acids; vinyl sulfonic acid, allyl sulfonic acid, An unsaturated sulfonic acid such as methallylsulfonic acid can be mentioned, and one or more selected from these can be used. Among these, at least one selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, vinyl sulfonic acid, allyl sulfonic acid and methallyl sulfonic acid is preferable.

1.1.3. Repeating unit derived from unsaturated carboxylic acid ester The water-soluble polymer (A) may further have a repeating unit derived from an unsaturated carboxylic acid ester. When the water-soluble polymer (A) has a repeating unit derived from an unsaturated carboxylic acid ester, the ratio of the repeating unit derived from the unsaturated carboxylic acid ester contained in 100 parts by mass of the water-soluble polymer (A) is 0-30 parts by mass is preferable, and 1-10 parts by mass is more preferable. By containing the repeating unit derived from the unsaturated carboxylic acid ester in the above range, the water-soluble polymer (A) has a more favorable affinity with the electrolytic solution, and the binder in the electricity storage device is an electrical resistance component. It is possible to prevent an increase in internal resistance due to the above and to prevent a decrease in adhesion due to excessive absorption of the electrolytic solution.

  The unsaturated carboxylic acid ester is preferably a (meth) acrylic acid ester. Specific examples of such (meth) acrylic acid esters include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, (meth ) N-butyl acrylate, i-butyl (meth) acrylate, n-amyl (meth) acrylate, i-amyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, (meth ) Monofunctional (meth) acrylate esters such as 2-ethylhexyl acrylate, n-octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate; glycidyl (meth) acrylate, (meth) Hydroxymethyl acrylate, hydroxyethyl (meth) acrylate, ethylene glycol (meth) acrylate, di (meth) Ethylene glycol crylate, propylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, allyl (meth) acrylate, etc. A polyfunctional (meth) acrylic acid ester; a compound represented by the following general formula (2); (meth) acrylic acid 3 [4 [1-trifluoromethyl-2,2-bis [bis (trifluoromethyl) fluoro Fluorine-containing (meth) acrylic acid esters such as methyl] ethynyloxy] benzooxy] 2-hydroxypropyl can be mentioned, and one or more selected from these can be used.

（式（２）中、Ｒ^２は水素原子またはメチル基であり、Ｒ^３はフッ素原子を含有する炭素数１〜１８の炭化水素基である。）

(In the formula (2), ^{R 2} is a hydrogen atom or a methyl group, ^{R 3} is a hydrocarbon group having 1 to 18 carbon atoms containing a fluorine atom.)

  In addition, the “polyfunctional (meth) acrylic acid ester” in the present invention means other polymerizable double bond, epoxy group, in addition to one polymerizable double bond possessed by (meth) acrylic acid ester, It means having at least one functional group selected from the group consisting of hydroxy groups.

  Among the monofunctional (meth) acrylic esters exemplified above, selected from the group consisting of methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate Is preferably at least one selected from the group consisting of methyl (meth) acrylate.

  Among the polyfunctional (meth) acrylic acid esters exemplified above, it is at least one selected from the group consisting of glycidyl (meth) acrylate, hydroxymethyl (meth) acrylate and hydroxyethyl (meth) acrylate. Of these, glycidyl (meth) acrylate is particularly preferable.

1.1.4. Repeating unit derived from α, β-unsaturated nitrile compound The water-soluble polymer (A) may further have a repeating unit derived from the α, β-unsaturated nitrile compound. When the polymer (A) has a repeating unit derived from an α, β-unsaturated nitrile compound, the repeating derived from the α, β-unsaturated nitrile compound contained in 100 parts by mass of the water-soluble polymer (A) The ratio of the unit is preferably 0 to 30 parts by mass, and more preferably 1 to 10 parts by mass. By containing the repeating unit derived from the α, β-unsaturated nitrile compound in the above range, the affinity of the water-soluble polymer (A) for the electrolytic solution is improved, so that the electrolytic solution absorption ability is improved. That is, the presence of the nitrile group makes it easy for the solvent to uniformly diffuse into the network structure formed of polymer chains formed in the electrode, so that the solvated lithium ions can easily move through the network structure. Thereby, it is thought that the diffusibility of lithium ion improves, As a result, electrode resistance falls and it is thought that a more favorable charge / discharge characteristic can be implement | achieved.

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

1.1.5. Repeating unit derived from other monomer The water-soluble polymer (A) may further contain a repeating unit derived from a conjugated diene compound or an aromatic vinyl compound.

  Examples of the conjugated diene compound include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene and the like. , One or more selected from these.

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

  In addition, since the water-soluble polymer (A) has a low oxidation potential when used in an environment exposed to a high voltage, the repeating unit derived from the conjugated diene compound and the repeating unit derived from the aromatic vinyl compound are substantially included. It is preferably not included. Examples of the environment exposed to high voltage include positive electrodes such as lithium ion batteries, lithium ion capacitors, and electric double layer capacitors, and protective films formed between the positive electrode surface and the separator.

1.1.6. Characteristics of water-soluble polymer (A) 1.1.6.1. Molecular weight of water-soluble polymer (A) The weight average molecular weight (Mw) of the water-soluble polymer (A) is preferably in the range of 300,000 to 6 million, more preferably 550,000 to 4.5 million. , 600,000 to 3,000,000 is particularly preferable. When the binder composition for an electricity storage device according to the present embodiment contains the water-soluble polymer (A) having the above-described molecular weight range, good charge / discharge characteristics are easily developed. The reason is not necessarily clear, but is presumed as follows.

  That is, when the molecular weight of the polymer is less than 300,000, there is a high possibility that the polymer will elute into the electrolyte solution. In this case, not only the adhesiveness is lowered, but also there is a risk that the low molecular weight polymer component eluted in the electrolytic solution is adversely affected on the charge / discharge characteristics such as being electrolyzed during the charge / discharge. On the other hand, when the molecular weight exceeds 6 million, there is a risk that the binder does not swell sufficiently depending on the electrolyte. The water-soluble polymer (A) according to the present embodiment is considered to have further improved charge / discharge characteristics by having a sufficiently large molecular weight as described above.

  The weight average molecular weight (Mw) / number average molecular weight (Mn) of the water-soluble polymer (A), the so-called dispersion ratio, is preferably 3-30, preferably 7-30, and 10-30. It is more preferable. Generally, the value of the dispersion ratio is considered to mean the spread of the molecular weight distribution, and the closer this value is to 1, the narrower the molecular weight distribution is. When the electricity storage device binder composition according to the present embodiment contains the water-soluble polymer (A) having a specific spread in the above-described range, good charge / discharge characteristics are easily exhibited. The reason is not necessarily clear, but is presumed as follows.

In general, in the case of a polymer having a narrow molecular weight distribution, i.e., a uniform molecular weight, the strength is increased when the molecular weight is large, but it tends to be brittle, and the polymer tends to be flexible when the molecular weight is small. There is a trade-off relationship that the strength decreases. On the contrary, when the molecular weight distribution is wide, that is, when a wide range from high molecular weight to low molecular weight is mixed, the ultra-high molecular weight polymer is excessively contained, so that the viscosity and thixotropy become extremely large when made into a solution. Tend. When this is applied to the application of the present invention, a slurry having good dispersibility and fluidity can be prepared by using a polymer having a specific molecular weight distribution. An electrode or a protective film formed from a slurry having good dispersibility and fluidity has characteristics that it is uniform and has few structural defects. In addition, by having a specific molecular weight distribution, it is possible to form a high-strength electrode while maintaining flexibility, so that the uniformity of the structure is less likely to be lost, and good initial characteristics can be maintained, resulting in durability. It is considered to be an excellent electrode and protective film.

  In addition, the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the water-soluble polymer (A) can be obtained, for example, by converting a measured value by a GPC (gel permeation chromatography) method into standard polyethylene oxide. it can.

1.1.6.2. Degree of neutralization of water-soluble polymer (A) When the water-soluble polymer (A) has an acid group, the degree of neutralization can be appropriately adjusted according to the use. The degree of neutralization when the active material or filler is dispersed is not particularly limited, but is preferably 0.7 to 1.0 and preferably 0.85 to 1.0 after the formation of the electrode or the protective film. Is more preferable. By setting the degree of neutralization after electrode preparation within the above range, most of the acid is in a neutralized state and is preferably combined with Li ions or the like in the battery and does not cause a decrease in capacity. Examples of the neutralized salt include Li salt, Na salt, K salt, ammonium salt, Mg salt, Ca salt, Zn salt, Al salt and the like.

1.1.7. Production Method of Water-Soluble Polymer (A) The method for synthesizing the water-soluble polymer (A) is not particularly limited, but polymerization performed in a solvent containing water as a main component is preferable. A particularly preferred polymerization form is aqueous solution polymerization. The polymerization initiator used in the synthesis of the water-soluble polymer (A) is preferably a water-soluble radical initiator, and is a persulfate such as lithium persulfate, potassium persulfate, sodium persulfate, ammonium persulfate or 4,4′-azobis. Water-soluble azo initiators such as (4-cyanovaleric acid) are particularly preferred. From the viewpoint of obtaining the water-soluble polymer (A) having the above-mentioned weight average molecular weight (300,000 to 6,000,000), the amount of the polymerization initiator used is 0. It is preferable that it is 1-1.0 mass parts.

  The polymerization temperature during the synthesis of the water-soluble polymer (A) is not particularly limited, but the synthesis is carried out in the range of 30 to 95 ° C. in consideration of the production time and the conversion rate (reaction rate) of the monomer to the copolymer. It is preferable to carry out, and 50-85 degreeC is especially preferable. However, in order to obtain a water-soluble polymer (A) having a target molecular weight or molecular weight distribution, it is necessary to control the set temperature during polymerization once within ± 3 ° C. Further, at the time of polymerization, it is also possible to use a pH adjuster, EDTA which is a metal ion sealing agent or a salt thereof for the purpose of improving production stability.

  In addition, pH may be adjusted with a general neutralizing agent such as ammonia, organic amine, potassium hydroxide, sodium hydroxide, lithium hydroxide before the polymerization or when water-solubilizing the polymer. It is preferable to adjust the pH to the range of 5-11. It is also possible to use EDTA which is a metal ion sealing agent or a salt thereof.

In particular, in order to control the molecular weight and molecular weight distribution of the water-soluble polymer (A), the type and amount of the initiator, the temperature control during the polymerization, the time until the total amount of monomer is added, after the total amount of monomer is added Temperature management and temperature holding time are important. For example, in the synthesis of the polymer described in JP 2012-151108 A, about 2 parts by mass of an initiator (ammonium persulfate) is used with respect to 100 parts by mass of the monomer. Generally, when the amount of the initiator increases with respect to the amount of the monomer, the molecular weight decreases, but it is considered that the above-described weight average molecular weight cannot be reached by such a synthesis method. In addition, since the water-soluble polymer (A) is obtained by radical polymerization in a solvent containing water as a main component, temperature control and reaction time are strictly controlled in order to synthesize a polymer having a desired molecular weight. There is a need to. Such time and temperature management needs to be adjusted in a timely manner according to the type of monomer used. For example, when controlling the molecular weight and molecular weight distribution of a water-soluble polymer (A) containing 40 to 100 parts by mass of repeating units derived from (meth) acrylamide with respect to 100 parts by mass of all repeating units, temperature control during polymerization It is necessary to carry out at about ± 3 ° C. with respect to the set temperature, and the time until addition of the whole amount of monomer needs to be carried out within about ± 5 minutes with respect to the set time. The control must be performed at about ± 3 ° C., and must be strictly controlled to the temperature holding time after addition of the entire amount of monomer.

1.2. Compound (B)
The binder composition for an electricity storage device according to the present embodiment contains at least one compound (B) selected from the group consisting of unsaturated carboxylic acids, unsaturated amides, and salts thereof. When the binder composition for an electricity storage device according to the present embodiment contains the compound (B), the charge / discharge characteristics of the obtained electricity storage device are improved. The expression mechanism of this effect is not necessarily clear, but is estimated as follows. In general, when a new component is added to a dispersion of active material particles, filler particles, or the like, the new component is a trigger, and aggregation of these particles is likely to occur. Nevertheless, when the slurry for an electricity storage device is prepared by mixing the binder composition for an electricity storage device to which the compound (B) is added and the active material particles or filler particles, non-uniformity is caused by the aggregation of the active material particles and the filler particles. Has been confirmed to be significantly suppressed. The reason for this is considered to be that the compound (B) is excellent in affinity with the active material particles and filler particles. As a result, the homogeneity of the coating film formed on the surface of the current collector, electrode and separator is improved, so that the adhesion between them and the coating film is improved, and the charge / discharge characteristics of the electricity storage device are improved. It is guessed.

  Moreover, it is thought that the fluidity | liquidity of the slurry for electrical storage devices can be improved by adding a compound (B) to the binder composition for electrical storage devices. If the fluidity of the slurry for an electricity storage device is improved, a coating film with a more uniform thickness can be formed, and it is assumed that the charge / discharge characteristics of the electricity storage device are improved.

  Furthermore, when the electrode material slurry is prepared by mixing the power storage device binder composition according to the present embodiment and the active material, and the slurry is applied to the surface of the current collector to form the active material layer, It is considered that the metal oxide layer formed on the surface of the current collector by the compound (B) contained in the slurry can be removed, and as a result, the electrical characteristics are improved. For example, when the current collector is an aluminum foil, it is a well-known fact that a passive aluminum oxide film is formed on the surface of the aluminum foil. Such an aluminum oxide film is insulative and tends to increase internal resistance in electrode formation. However, it is considered that when the binder composition for an electricity storage device of the present invention is used, such an insulating aluminum oxide film can be removed by the action of an acid or a base, so that charge / discharge characteristics can be improved.

  The content rate of the compound (B) in the binder composition for electrical storage devices which concerns on this Embodiment is 0.01-0.5 mass part with respect to 100 mass parts of said water-soluble polymers (A). Is preferable, 0.02 to 0.4 parts by mass is more preferable, and 0.03 to 0.3 parts by mass is particularly preferable. When the content ratio of the compound (B) is in the above range, not only the above-mentioned effects are sufficiently obtained, but also the storage stability of the binder composition for an electricity storage device is improved, which is preferable.

  Specific examples of such compound (B) include unsaturated carboxylic acids, unsaturated amides, and salts thereof. Hereinafter, “unsaturated carboxylic acid and salt thereof” may be referred to as “unsaturated carboxylic acid (salt)”, and “unsaturated amide and salt thereof” may be referred to as “unsaturated amide (salt)”.

1.2.1. Unsaturated carboxylic acid (salt)
Unsaturated carboxylic acids (salts) are susceptible to decarboxylation when heated, and are easily decomposed into low molecular weight components. For this reason, when the compound (B) is an unsaturated carboxylic acid (salt), the compound (B) remaining in the coating film evaporates when heated for drying the coating film in the electrode manufacturing process or the separator manufacturing process. In addition, it is considered that even if it is gradually decomposed and remains, it can be removed from the coating film to an amount that does not adversely affect the electricity storage device characteristics. As a result, since the corrosion of the current collector with the compound (B) is suppressed over time, it is considered that deterioration of the electricity storage device characteristics can be suppressed and stable charge / discharge characteristics can be expressed.

  Note that when an inorganic acid that is not a carboxylic acid is used, the current collector surface is severely corroded, which is not suitable for use. In addition, even after the slurry for the electricity storage device is applied to the surface of the current collector and dried, the inorganic acid remains in the coating film, and corrosion progresses over time, resulting in an electricity storage device that cannot exhibit stable charge / discharge characteristics. Therefore, it is not preferable.

  When an unsaturated carboxylic acid (salt) is used as the compound (B), the unsaturated carboxylic acid (salt) has an acid dissociation index (pKa) at 25 ° C. in at least one dissociation stage of 5.0 or more. It is preferable that In this specification, the “acid dissociation index (pKa)” refers to the pKa value of the second carboxy group for an organic acid having two carboxy groups, and 3 for an organic acid having three or more carboxy groups. The pKa value of the carboxy group is used as an index. When the acid dissociation index (pKa) is 5.0 or more, the metal oxide layer that can be formed on the surface of the current collector with the above-described addition amount can be easily removed, and the remaining in the active material layer can be suppressed. Therefore, it is preferable.

  Note that the acid dissociation index (pKa) is, for example, (a) The Journal of Physical Chemistry vol. 68, number 6, page 1560 (1964), (b) a method using an automatic potentiometric titrator (COM-980Win, etc.) manufactured by Hiranuma Sangyo Co., Ltd., and (c) Chemical Society of Japan It is possible to use the acid dissociation index described in the chemical manual of the edition (revised edition 3, June 25, 1984, published by Maruzen Co., Ltd.), (d) a database such as pKaBASE manufactured by Comprugrug, etc. it can.

  Specific examples of such unsaturated carboxylic acids (salts) include acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, malonic acid, citric acid, acetic acid, and salts thereof. It is done. Among these, acrylic acid, methacrylic acid, itaconic acid, acetic acid, and salts thereof are preferable. These unsaturated carboxylic acids (salts) can be used alone or in combination of two or more.

1.2.2. Unsaturated amide (salt)
The unsaturated amide (salt) preferably has a polymerizable unsaturated group from the viewpoint of improving adhesion, and more preferably has a (meth) acrylamide group. Specific examples of the unsaturated amide (salt) include acrylamide, methacrylamide, N-methylol acrylamide, N-methylol crotonamide, N-butoxymethyl acrylamide, N-butoxymethyl methacrylamide, diacetone acrylamide, diacetone methacrylamide, Aminopropylacrylamide, aminopropylmethacrylamide, monomethylacrylamide, monomethylmethacrylamide, monoethylacrylamide, monoethylmethacrylamide, N- (2-hydroxyethyl) acrylamide, N- (2-hydroxyethyl) methacrylamide, N- (2 -Hydroxypropyl) acrylamide, N- (2-hydroxypropyl) methacrylamide, N, N-dimethylacrylamide, N, N-dimethylmethacrylate Bromide, N, N- diethyl acrylamide, N, N- diethyl methacrylamide, N- isopropylacrylamide, N- acryloyl morpholine, and the like. It can be one or more selected from these. Among these, acrylamide, methacrylamide, N, N-dimethylacrylamide, N, N-diethylacrylamide, and N-isopropylacrylamide are preferable. These unsaturated amides (salts) can be used alone or in combination of two or more.

1.3. Liquid medium (C)
The binder composition for an electricity storage device according to the present embodiment contains a liquid medium (C). The liquid medium (C) is preferably an aqueous medium containing water. This aqueous medium can contain a non-aqueous medium other than water. Examples of the non-aqueous medium include amide compounds, hydrocarbons, alcohols, ketones, esters, amine compounds, lactones, sulfoxides, sulfone compounds, and the like. Use one or more selected from these. Can do. When the liquid medium (C) is an aqueous medium, 90% by mass or more is preferably water, and more preferably 98% by mass or more is water in the total amount of 100% by mass of the liquid medium (C). By using an aqueous medium as the liquid medium (C), the binder composition for an electricity storage device according to the present embodiment decreases the degree of adverse effects on the environment and increases the safety for handling workers.

  The content ratio of the non-aqueous medium contained in the aqueous medium is preferably 10% by mass or less, more preferably 5% by mass or less, particularly not substantially contained in 100% by mass of the aqueous medium. preferable. Here, “substantially does not contain” means that a non-aqueous medium is not intentionally added as the liquid medium (C), and is unavoidably mixed when preparing the binder composition for an electricity storage device. Non-aqueous media may be included.

2. Power Storage Device Slurry As described above, the power storage device binder composition according to the present embodiment can be broadly divided into two uses, that is, a use for producing a power storage device electrode and a use for producing a protective film. The power storage device slurry according to the present embodiment can also be classified into two types depending on the application. Hereinafter, the slurry for the electricity storage device used for the purpose of producing the electricity storage device electrode is referred to as “slurry for the electricity storage device electrode”, and the slurry for the electricity storage device used for the purpose of producing the protective film is referred to as the “slurry for the protection film”. And

2.1. Storage device electrode slurry "Storage device electrode slurry" refers to a dispersion liquid used to form an active material layer on a current collector surface after it is applied to the current collector surface and then dried. That means. The slurry for an electricity storage device electrode according to the present embodiment contains the above-mentioned binder composition for an electricity storage device and an active material. The slurry for an electricity storage device electrode according to the present embodiment can be used for an application for producing either a positive electrode or a negative electrode. Hereinafter, components contained in the slurry for the electricity storage device electrode according to the present embodiment will be described in detail. However, since it is as having mentioned above about the binder composition for electrical storage devices, description is abbreviate | omitted.

2.1.1. Active material There is no restriction | limiting in particular as a material which comprises the active material contained in the slurry for electrical storage device electrodes which concerns on this Embodiment, According to the kind of target electrical storage device, a suitable material can be selected suitably. Examples of the active material include carbon materials, silicon materials, oxides containing lithium atoms, lead compounds, tin compounds, arsenic compounds, antimony compounds, aluminum compounds, and the like.

  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. Moreover, since the transition metal existing on the surface of the active material is oxidized and becomes an oxide having a hydroxyl group on the surface when the active material contains these transition metals, the binding force with the binder is also 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.

Moreover, when using a silicon material as an active material, you may use together active materials other than a silicon material. Examples of such active materials include the above carbon materials; conductive polymers such as polyacene; A _X B _Y O _Z (where A is an alkali metal or transition metal, B is cobalt, nickel, aluminum, tin, manganese) At least one selected from transition metals such as O represents an oxygen atom, and X, Y and Z are 1.10>X> 0.05, 4.00>Y> 0.85, 5.00>, respectively. Z> 1.5 is a number in the range.) And other metal oxides. Among these, it is preferable to use a carbon material in combination because the volume change associated with insertion and extraction of lithium is small.

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.

  The shape of the active material is preferably granular. The average particle size of the active material is preferably 0.1 to 100 μm, and more preferably 0.5 to 20 μm.

  The active material is preferably used in such a ratio that the content of the binder (water-soluble polymer (A)) is 0.1 to 25 parts by mass with respect to 100 parts by mass of the active material. More preferably, it is used at a ratio of ˜15 parts 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.

2.1.2. Other Additives A conductive additive, a non-aqueous medium, a thickener, a pH adjuster, a corrosion inhibitor, and the like can be added to the electricity storage device electrode slurry according to the present embodiment as necessary.

2.1.2.1. Conductive aids Specific examples of conductive aids include carbon in lithium ion secondary batteries; in nickel metal hydride secondary batteries, cobalt oxide at the positive electrode: nickel powder, cobalt oxide, titanium oxide, carbon at the negative electrode, etc. Are used respectively. In both the batteries, examples of carbon include graphite, activated carbon, acetylene black, furnace black, graphite, carbon fiber, and fullerene. Among these, acetylene black or furnace black can be preferably used. The use ratio of the conductive assistant is preferably 20 parts by mass or less, more preferably 1 to 15 parts by mass, and particularly preferably 2 to 10 parts by mass with respect to 100 parts by mass of the active material.

2.1.2.2. Non-Aqueous Medium The slurry for an electricity storage device electrode according to the present embodiment can contain a non-aqueous medium having a standard boiling point of 80 to 350 ° C. from the viewpoint of improving the applicability. Specific examples of such a non-aqueous medium include, for example, amide compounds such as N-methylpyrrolidone, dimethylformamide, and N, N-dimethylacetamide; hydrocarbons such as toluene, xylene, n-dodecane, and tetralin; 2-ethyl Alcohols such as -1-hexanol, 1-nonanol, and lauryl alcohol; ketones such as methyl ethyl ketone, cyclohexanone, phorone, acetophenone, and isophorone; esters such as benzyl acetate, isopentyl butyrate, methyl lactate, ethyl lactate, and butyl lactate; o-toluidine, Examples include amine compounds such as m-toluidine and p-toluidine; lactones such as γ-butyrolactone and δ-butyrolactone; sulfoxide and sulfone compounds such as dimethyl sulfoxide and sulfolane, and the like. One or more selected from the above can be used. Among these, it is preferable to use N-methylpyrrolidone from the viewpoint of workability when applying the slurry for the electricity storage device electrode.

2.1.2.3. Thickener The slurry for an electricity storage device electrode according to the present embodiment can contain a thickener from the viewpoint of adjusting its fluidity and stability. Examples of such thickeners include cellulose compounds such as carboxymethyl cellulose, methyl cellulose, and hydroxypropyl cellulose; ammonium salts or alkali metal salts of the above cellulose compounds; poly (meth) acrylic acid, modified poly (meth) acrylic acid, and the like. Polycarboxylic acids of the above; alkali metal salts of the above polycarboxylic acids; polyvinyl alcohol (co) polymers such as polyvinyl alcohol, modified polyvinyl alcohol, ethylene-vinyl alcohol copolymers; (meth) acrylic acid, maleic acid and fumaric acid And water-soluble polymers such as saponified products of copolymers of unsaturated carboxylic acids and vinyl esters. Among these, particularly preferred thickeners include alkali metal salts of carboxymethyl cellulose and alkali metal salts of poly (meth) acrylic acid.

  In addition, when using in the environment exposed to a high voltage, it is preferable not to contain carboxymethylcellulose and its salt since oxidation potential is low. By adding carboxymethyl cellulose and its salt, the flexibility of the electrode may be reduced, and the winding property may be impaired, or the adhesion of the active material layer may be insufficient. Examples of the environment exposed to high voltage include positive electrodes such as lithium ion batteries, lithium ion capacitors, and electric double layer capacitors, and protective films formed between the positive electrode surface and the separator.

  When the electricity storage device electrode slurry according to the present embodiment contains a thickener, the use ratio of the thickener is preferably 20% by mass or less with respect to the total solid content of the electricity storage device electrode slurry. More preferably, it is 0.1-15 mass%, Most preferably, it is 0.5-10 mass%.

2.1.2.4. pH adjusting agent, corrosion inhibitor The slurry for the electricity storage device electrode according to the present embodiment is prepared by adding a pH adjusting agent or a corrosion inhibitor for the purpose of suppressing the corrosion of the current collector to be applied according to the type of the active material. Can be contained.

  Examples of the pH adjuster include hydrochloric acid, phosphoric acid, sulfuric acid, acetic acid, formic acid, ammonium phosphate, ammonium sulfate, ammonium acetate, ammonium formate, and ammonium chloride, and sulfuric acid and ammonium sulfate are preferable.

  Corrosion inhibitors include ammonium metavanadate, sodium metavanadate, potassium metavanadate, ammonium metatungstate, sodium metatungstate, potassium metatungstate, ammonium paratungstate, sodium paratungstate, potassium paratungstate, and molybdic acid. Ammonium, sodium molybdate, potassium molybdate and the like can be mentioned, and ammonium paratungstate, ammonium metavanadate, sodium metavanadate, potassium metavanadate and ammonium molybdate are preferable.

2.1.3. Method for producing power storage device electrode slurry The power storage device electrode slurry according to the present embodiment is a mixture of the power storage device binder composition described above, an active material, water, and an additive used as necessary. Can be manufactured. These mixing can be performed by stirring by a known method, and for example, a stirrer, a defoamer, a bead mill, a high-pressure homogenizer, or the like can be used.

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

2.2. "Slurry for protective film""Slurry for 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. The slurry for protective films which concerns on this Embodiment contains the binder composition for electrical storage devices mentioned above and a filler. Hereinafter, each component contained in the slurry for protective films according to the present embodiment will be described in detail. In addition, since it is as having mentioned above about the binder composition for electrical storage devices, description is abbreviate | omitted.

2.2.1. Filler The slurry for a protective film according to the present embodiment can improve the toughness of the formed protective film by containing a filler. As the filler, silica, titanium oxide (titania), aluminum oxide (alumina), zirconium oxide (zirconia), magnesium oxide (magnesia), or the like can be used. Among these, titanium oxide and aluminum oxide are preferable from the viewpoint of further improving the toughness of the protective film. Further, as the titanium oxide, rutile type titanium oxide is more preferable.

  The average particle size of the filler is preferably 1 μm or less, and more preferably in the range of 0.1 to 0.8 μm. In addition, it is preferable that the average particle diameter of a filler 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 a filler can be prevented from being clogged with the micropore of a separator.

  The protective film slurry according to the present embodiment preferably contains 0.1 to 20 parts by mass of the above-mentioned binder (water-soluble polymer (A)) with respect to 100 parts by mass of the filler. More preferably, 10 parts by mass is contained. When the content ratio of the binder is 0.1 to 10 parts by mass, the balance between the toughness of the protective film to be formed and the lithium ion permeability is improved, and as a result, the resistance increase rate of the obtained electricity storage device is further increased. Can be lowered.

2.2.2. Other Additives The protective film slurry according to the present embodiment may contain the materials and addition amounts described in the above-mentioned “2.1.2. Other Additives” slurry for an electricity storage device electrode as necessary. It can be used as needed.

2.2.3. Production Method of Protective Film Slurry The protective film slurry according to the present embodiment is prepared by mixing the above-mentioned binder composition for an electricity storage device, a filler, and an additive used as necessary. . As a means for mixing them, for example, a known mixing device such as a ball mill, a sand mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, a planetary mixer, a Hobart mixer can be used.

  For mixing and stirring for producing the protective film slurry according to the present embodiment, it is necessary to select a mixer that can stir to such an extent that filler aggregates do not remain in the slurry and, if necessary, sufficient dispersion conditions. There is. The degree of dispersion can be measured by a particle gauge, but it is preferable to mix and disperse so that aggregates larger than at least 100 μm are eliminated. Examples of the mixer that meets such conditions include a ball mill, a sand mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, a planetary mixer, and a Hobart mixer.

2.3. Slurry characteristics The slurry for an electricity storage device according to the present embodiment preferably has a spinnability of 30 to 80%, more preferably 33 to 79%, and particularly preferably 35 to 78%. . When the spinnability is less than the above range, the leveling property is insufficient when applying the slurry, and thus the uniformity of the thickness of the coating film may be impaired. If an electrode or a protective film having a non-uniform thickness is used, an in-plane distribution of charge / discharge reaction occurs, making it difficult to achieve stable battery performance. On the other hand, if the spinnability exceeds the above range, dripping easily occurs when applying the slurry, and it is difficult to obtain a stable quality electrode or protective film. Therefore, if the spinnability is within the above range, the occurrence of these problems can be suppressed, and it becomes easy to manufacture an electricity storage device having both good electrical characteristics and adhesion.

The “threadability” in the present specification is a physical property measured as follows. First, a Zaan cup (made by Dazai Equipment Co., Ltd., Zaan Bisco City Cup No. 5) having an opening with a diameter of 5.2 mm at the bottom is prepared. With this opening closed, 40 g of slurry is poured into the Zahn cup. Thereafter, when the opening is opened, the slurry flows out from the opening. Here, it is possible to obtain T ₀ when opening the _opening, the T _A when the slurry of the thread is _finished, when the outflow of the slurry is completed when the T _B, the following equation (3) .
Spinnability (%) = ((T _A −T ₀ ) / (T _B −T ₀ )) × 100 (3)

3. The electricity storage device electrode according to the present embodiment includes a current collector and a layer formed by applying and drying the above-mentioned slurry for an electricity storage device electrode on the surface of the current collector. is there. Such an electricity storage device electrode is formed by applying the aforementioned 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 to form an active material layer. Can be manufactured. The electricity storage device electrode thus manufactured is formed by binding an active material layer containing the above-described binder, active material, and optional components added as necessary, on a current collector. Such an electricity storage device electrode has excellent adhesion between the current collector and the active material layer, and therefore has good charge / discharge rate characteristics, which is one of the electrical characteristics.

The current collector is not particularly limited as long as it is made of a conductive material. In the lithium ion secondary battery, a current collector made of metal such as iron, copper, aluminum, nickel, and stainless steel is used. Especially when aluminum is used for the positive electrode and copper is used for the negative electrode, the above-mentioned storage device is used. The effect of the slurry for an electricity storage device electrode produced using the binder composition 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 coating amount of the power storage device electrode slurry is not particularly limited, but the thickness of the active material layer formed after removing the liquid medium (which is a concept including both water and a non-aqueous medium that is optionally used). However, it is preferable to set it as the quantity used as 0.005-5 mm, and it is more preferable to set it as the quantity used as 0.01-2 mm. When the thickness of the active material layer is within the above range, the active material layer can be effectively infiltrated with the electrolytic solution. As a result, it is preferable because the metal ions can be easily transferred between the active material and the electrolytic solution in the active material layer, so that the electrode resistance can be further reduced. In addition, since the thickness of the active material layer is within the above range, even when the electrode is folded or wound, the active material layer is not peeled off from the current collector. It is preferable at the point from which the electrical storage device electrode which is favorable and is rich in flexibility is obtained.

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

  Furthermore, it is preferable to increase the density of the active material layer by pressing the dried current collector and to adjust the porosity to the range shown below. Examples of the pressing method include a die press and a roll press. The press conditions should be set appropriately depending on the type of press equipment used and the desired values of the porosity and density of the active material layer. This condition can be easily set by a few preliminary experiments by those skilled in the art. For example, in the case of a roll press, the linear pressure of the roll press machine is 0.1 to 10 (t / cm), preferably 0. At a pressure of 5 to 5 (t / cm), for example, at a roll temperature of 20 to 100 ° C., the current collector feed speed (roll rotation speed) after drying is 1 to 80 m / min, preferably 5 to 50 m / min. It can be performed in min.

The density of the active material layer after pressing, preferably in the 1.5~5.0g / cm ^3, more preferably to 1.5~4.0g / cm ^3, 1.6~3.8g / Cm ³ is particularly preferable.

4). Protective film A protective film can be formed by applying the above-mentioned slurry for protective film on the surface of the positive electrode, negative electrode or separator and drying it. Specific embodiments of the protective film include the following three embodiments.

(1) As a 1st aspect, a protective film can be formed in the active material layer surface by apply | coating and drying the above-mentioned slurry for protective films on the active material layer surface of a positive electrode and / or a negative electrode.
(2) As a 2nd aspect, a protective film can be formed in the surface of a separator by apply | coating and drying the above-mentioned slurry for protective films directly on the separator surface.
(3) As a third aspect, when a functional layer is formed on the separator surface, the protective film is applied to the surface of the functional layer by applying the above-mentioned slurry for protective film on the surface of the functional layer and drying it. Can be formed.

  There is no particular limitation on the method of applying the protective film slurry to the positive electrode, negative electrode or separator. The coating can be performed by an appropriate method such as a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, a dipping method, or a brush coating method. The coating amount of the protective film slurry is not particularly limited, but the thickness of the protective film formed after removing the liquid medium is preferably 0.5 to 4 μm, and preferably 0.5 to 3 μm. It is more preferable to use the amount. When the thickness of the protective film is in the above range, the permeability of the electrolytic solution into the electrode and the liquid retaining property are improved, and an increase in the internal resistance of the electrode can be suppressed.

  There is no particular limitation on the drying method from the coated film after coating (method for removing water and optionally used non-aqueous medium); for example, drying with warm air, hot air, low humidity air; vacuum drying; (far) infrared , Drying by irradiation with an electron beam or the like. The drying speed 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. Specifically, the coating film is preferably dried at a temperature of 20 to 250 ° C., more preferably 50 to 150 ° C., preferably for 1 to 120 minutes, more preferably 5 to 60 minutes. be able to.

5. Power Storage Device The power storage device according to the present embodiment only needs to include at least one of the above-described power storage device electrode and the separator including the above-described protective film. As a specific method for manufacturing an electricity storage device, a positive electrode and a negative electrode are laminated with a separator for preventing a short circuit between the electrodes, or a positive electrode, a separator, a negative electrode, and a separator are laminated in this order to form an electrode. / Separator laminated body, this may be wound or folded according to the shape of the battery, put into a battery container, and an electrolyte solution is injected into the battery container and sealed. In addition, the shape of the battery can be an appropriate shape such as a coin shape, a button shape, a sheet shape, a cylindrical shape, a square shape, or a flat shape.

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

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

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

  The power storage device according to the present embodiment is suitable as a secondary battery or a capacitor mounted on an automobile such as an electric vehicle, a hybrid car, and a truck, and also used as a secondary battery used in AV equipment, OA equipment, communication equipment, and the like. It is also suitable as a battery or a capacitor.

6). 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.

6.1. Example 1
6.1.1. Synthesis and Evaluation of Water-Soluble Polymer (A) (1) Preparation of Aqueous Solution Containing Water-Soluble Polymer (A) The interior of a 7-L separable flask was sufficiently purged with nitrogen, and charged with 1050 parts by weight of water. The temperature was raised to 70 ° C., and then 0.3 part by mass of sodium persulfate was added. Next, a mixed solution of 110 parts by mass of water, 80 parts by mass of acrylamide, 10 parts by mass of acrylic acid, and 10 parts by mass of ethyl acrylate was added dropwise over 1 hour, and the reaction was performed at 70 ° C ± 3 ° C for 2 hours, The reaction was performed at ± 3 ° C. for 2 hours. Then, it cooled and adjusted to pH 7 with 20 wt% sodium hydroxide aqueous solution, and obtained the aqueous solution containing 8 wt% of water-soluble polymers (A). An aqueous solution containing 8 wt% of the water-soluble polymer (A) thus obtained was designated as a binder composition S1 for an electricity storage device. It was 3000 mPa * s when the binder composition S1 for electrical storage devices was adjusted to 25 degreeC, and the viscosity was measured using the BM type | mold viscosity meter.

(2) Measurement of molecular weight The weight average molecular weight (Mw) of the water-soluble polymer (A) measured under the following conditions is 6 × 10 ⁶ , and the value of weight average molecular weight (Mw) / number average molecular weight (Mn) ( The dispersion ratio) was 30.
・ Measurement equipment: GPC (model number: HLC-8220) manufactured by Tosoh Corporation
Column: TSKgel guardcolumn PW _XL (manufactured by Tosoh Corporation), TSK-GEL G2500PW _XL (manufactured by Tosoh Corporation), TSK-GEL GMPW _XL (manufactured by Tosoh Corporation)
Eluent: 0.1M NaNO ₃ aqueous solution Calibration curve: standard polyethylene oxide Measurement method: Dissolved in the eluent so that the concentration of the water-soluble polymer (A) is 0.3 wt%, and measured after filter filtration.

6.1.2. Preparation and Evaluation of Binder Composition for Electricity Storage Device (1) Preparation of Binder Composition for Electricity Storage Device To 100 parts by mass of the water-soluble polymer (A) in the aqueous solution containing the water-soluble polymer (A) obtained above. On the other hand, 0.03 parts by mass of acrylamide as the compound (B) was added and stirred at 150 rpm to prepare a binder composition for an electricity storage device.

In addition, content of the compound (B) in the binder composition for electrical storage devices can also be confirmed by analyzing the binder composition for electrical storage devices with the following procedures. That is, 0.2 g of the obtained binder composition for an electricity storage device was weighed, and 200 ppm maleic acid aqueous solution was added as an internal standard solution to dilute it 50 times. The measurement sample thus prepared was subjected to compound (B) using an ion chromatography apparatus (Tosoh Corporation: IC-2010, UV detector: UV-8320IC) using a TSKgelSCX (H +) column manufactured by Tosoh Corporation. ) Content of acrylamide was quantified. Based on this quantitative result, it was confirmed that the content of acrylamide with respect to 100 parts by mass of the water-soluble polymer (A) contained in the binder composition for an electricity storage device was 0.03 parts by mass.

(2) Sedimentation evaluation Generally, the binder composition for an electricity storage device is stored in large quantities for use in a factory for producing the electricity storage device. And the binder composition for electrical storage devices stored in large quantities is consumed sequentially as needed. At this time, the characteristics of the binder composition for an electricity storage device consumed first and the characteristics of the binder composition for an electricity storage device after being stored for a long period of time are not allowed to change as the polymer settles.

  100 g of polybin was filled with the binder composition for an electricity storage device prepared above and stored in a refrigerator set at 2 ° C. for one month. The storage device binder composition after storage was visually observed. When sedimentation was not observed, it was judged as good, and when sedimentation was observed, it was judged as poor and evaluated as x. The results of sedimentation evaluation are also shown in Table 1.

(3) Evaluation of freezing temperature In addition, the storage environment of the binder composition for an electricity storage device cannot be strictly controlled from the viewpoint of cost, and is therefore exposed to an environment near 0 ° C. due to changes in temperature. There are also many. For this reason, in the following evaluation of the freezing temperature, freezing at 0 ° C. is not acceptable, and the freezing temperature is required to be −0.5 ° C. or lower. Therefore, when the freezing temperature is −0.5 ° C. or lower, it can be determined that the stability of the binder composition for an electricity storage device is high and good.

  The freezing temperature of the binder composition for an electricity storage device was measured as follows. 1,000 g of polybin was filled with the binder composition for an electricity storage device prepared above and stored in a freezer at −10 ° C., and the temperature at which freezing started (freezing temperature) was measured. The measurement results are also shown in Table 1.

6.1.3. Preparation and Evaluation of Positive Electrode Slurry and Negative Electrode Slurry (1) Preparation of Positive Electrode Slurry A power storage device obtained above in a biaxial planetary mixer (trade name “TK Hibismix 2P-03” manufactured by PRIMIX Corporation) The binder composition S1 was added in an amount corresponding to 1.5 parts by mass in terms of the water-soluble polymer (A), and a commercially available nickel / manganese / cobalt acid lithium (nickel (D50 value) of 10 μm) Ni), cobalt (Co), manganese (Mn) ratio 1: 1: 1) 100 parts by mass of active material particles, 3 parts by mass of acetylene black, 0.5 parts by mass of sodium vanadate and 4 parts by mass of water were added, Stirring was performed at 90 rpm for 1 hour. After adding water to the obtained paste to adjust the solid content concentration to 70%, using a stirring defoaming machine (trade name “Awatori Nentaro” manufactured by Shinky Co., Ltd.) for 2 minutes at 200 rpm. The slurry for positive electrode was prepared by stirring and mixing at 800 rpm for 5 minutes and further under vacuum (about 5.0 × 10 ³ Pa) at 1,800 rpm for 1.5 minutes.

(2) Preparation of slurry for negative electrode A water-soluble polymer was prepared by using the biaxial planetary mixer (trade name “TK Hibismix 2P-03” manufactured by PRIMIX Corporation) and the binder composition S1 for an electricity storage device obtained above. (A) An amount corresponding to 1 part by mass is introduced, 100 parts by mass of graphite (in terms of solid content), 4 parts by mass of acetylene black, and 53 parts by mass of ion-exchanged water are introduced as the negative electrode active material. Stir for hours. After adding 40 parts by mass of water, using a stirring defoamer (product name “Awatori Nertaro” manufactured by Sinky Co., Ltd.) for 2 minutes at 200 rpm, then 5 minutes at 1,800 rpm, and further under vacuum A slurry for negative electrode was prepared by stirring and mixing at 1,800 rpm for 1.5 minutes at (about 5.0 × 10 ³ Pa).

(3) Measurement of the spinnability of the slurry The spinnability of the positive electrode slurry and the negative electrode slurry obtained above was measured as follows. First, a Zaan cup (Dazai Equipment Co., Ltd., Zaan Bisco City Cup No. 5) having an opening with a diameter of 5.2 mm at the bottom of the container was prepared. With the Zahn cup opening closed, 40 g of the slurry prepared above was poured. When the opening was opened, the slurry flowed out. In this case, the time instant of opening the opening and T _0, the time continued to flow out so as to draw the yarn when the slurry flows measured visually, the time was T _A. Moreover, to continue the measurement from no longer attracted yarn was measured time T _B until the slurry no longer flow out. The measured values T ₀ , T _A and T _B were substituted into the following formula (3) to determine the spinnability. As described above, when the spinnability of the slurry is 30 to 80%, it can be determined that the applicability on the current collector is good. The results are also shown in Table 2.
Spinnability (%) = ((T _A −T ₀ ) / (T _B −T ₀ )) × 100 (3)

6.1.4. Production and Evaluation of Positive Electrode and Negative Electrode (1) Production of Positive Electrode The positive electrode slurry prepared above is uniformly applied to the surface of the current collector made of aluminum foil by a doctor blade method so that the film thickness after drying becomes 110 μm. It was applied and dried at 120 ° C. for 10 minutes. Then, the positive electrode was obtained by pressing with a roll press so that the density of a film | membrane (active material layer) might be 3.0 g / cm < ³ >.

(2) Production of Negative Electrode The negative electrode slurry prepared above 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 110 μm. Dried for minutes. Then, the negative electrode was obtained by pressing using a roll press so that the density of a film | membrane (active material layer) might be 1.5 g / cm < ³ >.

(3) Evaluation of crack rate of electrode plate Each of the positive electrode plate and the negative electrode plate obtained above was cut into 2 cm width × 10 cm length, and the positive electrode plate was bent 100 times along a round bar having a diameter of 2 mm in the width direction. The bending test was repeatedly performed. The size of the crack along the round bar was visually observed and measured, and the crack rate was measured. The crack rate was defined by the following formula (4).
Crack rate (%) =
(Length with cracks (mm) ÷ Total length of electrode plate (mm)) × 100 (4)
The crack rate was evaluated in 5% increments by rounding off to make it easier to clarify the difference. Here, the electrode plate excellent in flexibility and adhesion has a low crack rate. The crack rate is preferably 0%. However, when the electrode plate group is manufactured by winding the positive electrode plate and the negative electrode plate in a spiral shape through a separator, the crack rate is allowed up to 20%. However, when the crack rate is greater than 20%, the electrode plates are easily cut, making it impossible to manufacture the electrode plate group, and the productivity of the electrode plate group is lowered. From this, it is considered that the crack rate is good within 20%. The results are also shown in Table 2.

6.1.5. Assembling and Evaluation of Lithium Ion Battery Cell (1) Assembling of Lithium Ion Battery Cell In the glove box substituted with Ar so that the dew point is -80 ° C. or lower, the negative electrode produced above was punched and molded to a diameter of 15.95 mm Was placed on a bipolar coin cell (trade name “HS flat cell” manufactured by Hosen Co., Ltd.). Next, a separator made of a polypropylene porous membrane punched into a diameter of 24 mm (trade name “Celguard # 2400” manufactured by Celgard Co., Ltd.) was placed, and after injecting 500 μL of an electrolyte solution so that air did not enter, A lithium ion battery cell (power storage device) was assembled by placing the positive electrode manufactured in the above-described method by punching and molding the positive electrode to a diameter of 16.16 mm, and sealing the outer body of the bipolar coin cell with a screw. The electrolytic solution used 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).

(2) Evaluation of charge / discharge rate characteristics With respect to the lithium ion battery cell produced above, charging was started at a constant current (0.2 C), and when the voltage reached 4.2 V, the constant voltage (4.2 V) was continued. ) Was continued, and when the current value reached 0.01C, the charging was completed (cut off), and the charge capacity at 0.2C was measured. Next, discharge was started at a constant current (0.2 C), and when the voltage reached 2.7 V, the discharge was completed (cut off), and the discharge capacity at 0.2 C was measured.

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

  Using the measured values above, calculate the charge rate (%) by calculating the ratio (percent%) of the charge capacity at 3C to the charge capacity at 0.2C at 3C versus the discharge capacity at 0.2C. The discharge rate (%) was calculated by calculating the discharge capacity ratio (percentage%). When both the charge rate and the discharge rate are 80% or more, it can be evaluated that the charge / discharge rate characteristics are good. The measured charge rate and discharge rate values are shown in Table 2, respectively.

6.2. Examples 2 to 16, Comparative Example 1
In “6.1.1. Synthesis and Evaluation of Water-Soluble Polymer (A)” in Example 1 above, the composition of the monomer and the amount of the initiator were appropriately changed, and “6. In “1.2. Preparation and evaluation of binder composition for electricity storage device”, the polymer having the composition shown in Table 1 was prepared in the same manner as in Example 1 except that the type and addition amount of compound (B) were appropriately changed. An aqueous solution (binder compositions S2 to S17 for power storage devices) was prepared, and the molecular weight of the obtained water-soluble polymer (A) was measured. The results are also shown in Table 1.

  Next, in Example 6 “6.1.3. Preparation and evaluation of slurry for positive electrode and negative electrode”, the amount of the polymer added and the type of the active material were as described in Table 2. In the same manner as in Example 1, positive electrode and negative electrode slurries were prepared, and the spinnability of the slurry was measured. The results are also shown in Table 2.

  Further, in the same manner as in “6.1.4. Production and evaluation of positive electrode and negative electrode” and “6.1.5. Assembly and evaluation of lithium ion battery cell” in Example 1, an electrode and an electricity storage device were produced. And evaluated. The results are also shown in Table 2.

6.3. Evaluation results of Examples 1 to 16 and Comparative Example 1 Table 1 below shows the monomer composition and molecular weight of the polymer contained in each binder composition for an electricity storage device, the content ratio of the compound (B), and evaluation results. Table 2 below shows the compositions of the positive electrode and negative electrode slurries and the evaluation results.

In addition, the abbreviation of each component in Table 1 has the following meaning, respectively.
AMM: acrylamide MAMMA: methacrylamide NMAM: N-methylol acrylamide ATBS: acrylamide t-butyl sulfonic acid AA: acrylic acid MAA: methacrylic acid VS: vinyl sulfonic acid AS: allyl sulfonic acid MAS: Methallylsulfonic acid, MMA: methyl methacrylate, MA: methyl acrylate, BA: n-butyl acrylate, EA: ethyl acrylate, HEMA: 2-hydroxyethyl methacrylate, AN: acrylonitrile, MAN: methacrylonitrile The notation “-” in 1 indicates that the corresponding component was not used or the corresponding operation was not performed.

Abbreviations of each component in Table 2 have the following meanings.
NMC (111): manufactured by Umicore, nickel, manganese, lithium cobaltate (nickel (Ni): cobalt (Co): manganese (Mn) is 1: 1: 1), grade name "MX-10"
NMC (532): manufactured by Umicore, nickel, manganese, lithium cobaltate (nickel (Ni): cobalt (Co): manganese (Mn) is 5: 3: 2), grade name "TX-10"
・ AB: Acetylene black (manufactured by Denki Black, Denka Black 50% press) ・ Graphite: Hitachi Chemical Co., Ltd., trade name “MAG”
NaVO ₃ : manufactured by Wako Pure Chemical Industries, Ltd., sodium metavanadate (V)

  As is apparent from Table 2 above, the slurry for an electricity storage device electrode prepared using the binder composition for an electricity storage device according to the present invention shown in Examples 1 to 16 has excellent spinnability and adhesion (for example, Since the binding property between the current collector and the active material layer and the binding property between the active materials were good, an excellent electrode having a low crack rate was obtained. Moreover, the electrical storage device (lithium ion battery) provided with these electrodes had favorable charge / discharge rate characteristics.

  On the other hand, with the binder composition for an electricity storage device shown in Comparative Example 1, a good slurry could not be obtained, and an electricity storage device showing good charge / discharge characteristics could not be obtained.

6.4. Example 17
6.4.1. Preparation of slurry for protective film Titanium oxide (product name “KR380”, manufactured by Titanium Industry Co., Ltd., rutile type, average particle size 0.38 μm) is 100 parts by mass with respect to 500 parts by mass of water. An amount corresponding to 5 parts by mass of the obtained binder composition S1 for an electricity storage device in terms of a water-soluble polymer (A) with respect to 100 parts by mass of the filler was calculated using T.P. K. Mixing and dispersing treatment was performed using a film mix (R) 56-50 type (manufactured by PRIMIX Co., Ltd.) to prepare a slurry for a protective film in which titanium oxide was dispersed. The spinnability of the protective film slurry thus obtained was evaluated in the same manner as in Example 1.

6.4.2. 3. Production of positive electrode Biaxial planetary mixer (product name “TK Hibismix 2P-03” manufactured by PRIMIX Corporation) and binder for electrochemical device electrode (product name “KF polymer # 1120” manufactured by Kureha Co., Ltd.) 0 parts by mass (converted to solid content), 3.0 parts by mass of conductive assistant (manufactured by Denki Kagaku Kogyo Co., Ltd., trade name “DENKA BLACK 50% press product”), LiCoO _{2 having a} particle diameter of 5 μm as a positive electrode active material (Hayashi Kasei) 100 parts by mass (manufactured by Corporation) (solid content conversion) and 36 parts by mass of N-methylpyrrolidone (NMP) were added and stirred at 60 rpm for 2 hours. After adding NMP to the obtained paste to adjust the solid content to 65%, using a stirring defoaming machine (trade name “Awatori Netaro”, manufactured by Shinky Co., Ltd.), 2 minutes at 200 rpm, 1800 rpm The slurry for positive electrode was prepared by stirring and mixing for 5 minutes at 1800 rpm for 1 minute at 1800 rpm. The obtained positive electrode slurry was uniformly applied to the surface of a current collector made of aluminum foil by a doctor blade method so that the film thickness after drying was 120 μm, followed by drying treatment at 120 ° C. for 20 minutes. Then, the positive electrode was obtained by pressing with a roll press so that the density of an active material layer might be 3.0 g / cm < ³ >.

  Next, the protective film slurry prepared above was applied to the surface of the active material layer using a die coating method, and then dried at 120 ° C. for 5 minutes to form a protective film on the surface of the active material layer. The formed protective film had a thickness of 3 μm. For the positive electrode thus obtained, the crack rate of the electrode plate (protective film) was evaluated in the same manner as in Example 1.

6.4.3. Negative electrode Biaxial planetary mixer (product name “TK Hibismix 2P-03” manufactured by PRIMIX Corporation), 4 parts by mass of polyvinylidene fluoride (PVDF) (in terms of solid content), and 100 parts by mass of graphite as a negative electrode active material ( Solid conversion), 80 parts by mass of N-methylpyrrolidone (NMP) were added, and the mixture was stirred at 60 rpm for 1 hour. Then, after adding 20 parts by mass of NMP, using a stirring defoaming machine (product name “Awatori Netaro” manufactured by Shinky Co., Ltd.) for 2 minutes at 200 rpm, then for 5 minutes at 1,800 rpm, further vacuum Below, the slurry for negative electrodes was prepared by stirring and mixing for 1.5 minutes at 1,800 rpm.

The negative electrode slurry prepared above 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 110 μm, and dried at 120 ° C. for 20 minutes. Then, the negative electrode was obtained by pressing using a roll-press machine so that the density of a film | membrane may be 1.5 g / cm < ³ >.

6.4.4. 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 15.95 mm in an Ar-substituted glove box with a dew point of −80 ° C. or lower. And product name “HS flat cell”). Next, a separator made of a polypropylene porous membrane punched into a diameter of 24 mm (trade name “Celguard # 2400” manufactured by Celgard Co., Ltd.) was placed, and after injecting 500 μL of an electrolyte solution so that air did not enter, The positive electrode manufactured in the above is punched and molded to a diameter of 16.16 mm and placed so that the protective film formed on the positive electrode and the separator face each other, and the outer body of the bipolar coin cell is closed with a screw and sealed. Thus, a lithium ion battery cell (electric storage device) was assembled. 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). Thus, about the obtained electrical storage device, it carried out similarly to the said Example 1, and evaluated charge / discharge rate characteristic.

6.5. Examples 18-24, Comparative Example 2
In Example 17, the protective film was used in the same manner as in Example 17 except that the binder composition for an electricity storage device used was changed to that shown in Table 3 and the filler used was that shown in Table 3. Slurry was prepared and its spinnability was evaluated. Further, a positive electrode was produced in the same manner as in Example 17 except that the protective film slurry used in Example 17 was changed to that shown in Table 3, and the crack rate was evaluated. Furthermore, after producing a negative electrode in the same manner as in Example 17, an electricity storage device was produced, and charge / discharge rate characteristics were similarly evaluated. These evaluation results are also shown in Table 3.

6.6. Examples 25-27, Comparative Example 3
In Example 17, the binder composition for an electricity storage device used was changed to that shown in Table 4, and the same procedure as in Example 17 was applied except that the filler used was that shown in Table 4. A membrane slurry was prepared and evaluated for spinnability. The evaluation results are also shown in Table 4.

  Next, a negative electrode is produced in the same manner as in Example 17, and the obtained protective film slurry is applied to the surface of the negative electrode active material layer using a die coating method, and then dried at 120 ° C. for 5 minutes. Thus, a protective film was formed on the surface of the active material layer. For the negative electrode thus obtained, the crack rate of the electrode plate (protective film) was evaluated in the same manner as in Example 17. The evaluation results are also shown in Table 4.

In addition, the battery was charged in the same manner as in Example 17 except that the positive electrode before forming the protective film produced in Example 17 was used as the positive electrode, and the negative electrode with protective film obtained above was used as the negative electrode. A device was manufactured (however, the negative electrode protective film and the separator were placed facing each other), and the charge / discharge rate characteristics, the remaining capacity rate, and the resistance increase rate were similarly evaluated. These evaluation results are also shown in Table 4.

6.7. Example 28
A wire bar was prepared by applying the slurry for the protective film prepared in Example 17 on one side of a separator made of a polypropylene porous film (trade name “Celguard # 2400” manufactured by Celgard Co., Ltd.) so that the thickness after drying was 10 μm. And then dried at 90 ° C. for 20 minutes to obtain a separator with a protective film. About the separator with a protective film thus obtained, the crack rate of the protective film was evaluated in the same manner as in Example 17. The evaluation results are also shown in Table 5.

  Furthermore, the positive electrode before the protective film produced in Example 17 was formed as the positive electrode, and the negative electrode produced in Example 17 was used as the negative electrode, and the protective film surface of the separator with the protective film obtained above was An electricity storage device was produced in the same manner as in Example 17 with the positive electrode side, and the charge / discharge rate characteristics were similarly evaluated. The results are also shown in Table 5.

6.8. Examples 29 to 35, Comparative Example 4
In Example 28, a separator with a protective film was prepared in the same manner as in Example 28 except that the binder composition for an electricity storage device and the filler used were changed to those shown in Table 5 to prepare a slurry for the protective film. A positive electrode, a negative electrode, and an electricity storage device were manufactured and evaluated in the same manner. The results are also shown in Table 5.

6.9. Examples 36 to 38, Comparative Example 5
In Example 28 above, the protective film slurry was prepared by changing the binder composition and filler for the electricity storage device used to those shown in Table 6 so that the protective film surface of the separator with the protective film was on the negative electrode side. A separator with a protective film, a positive electrode, a negative electrode, and an electricity storage device were produced in the same manner as in Example 28 except that the evaluation was performed in the same manner. The results are also shown in Table 6.

6.10. Evaluation Results of Examples 17 to 38 and Comparative Examples 2 to 5 Tables 3 to 6 below show the composition of the slurry for the protective film and each evaluation result.

The fillers described in Tables 3 to 6 are as follows.
Titanium oxide: The product name “KR380” (manufactured by Titanium Industry Co., Ltd., rutile type, average particle size 0.38 μm) is used as it is, or is ground in a mortar with the product name “KR380” and used with a sieve. By classification, titanium oxides having an average particle diameter of 0.08 μm and 0.12 μm were prepared and used.
Aluminum oxide: Product name “AKP-3000” (manufactured by Sumitomo Chemical Co., Ltd., average particle size 0.74 μm), or product name “AL-160SG-3” (manufactured by Showa Denko KK, average particle size 0.98 μm) Was used.
Zirconium oxide: Product name “UEP zirconium oxide” (Daiichi Rare Element Chemical Industries, Ltd., average particle size 0.67 μm)
Silica: The product name “Sea Hoster (R) KE-S50” (manufactured by Nippon Shokubai Co., Ltd., average particle size 0.54 μm) was used.
Magnesium oxide: Product name “PUREMAG® FNM-G” (manufactured by Tateho Chemical Industry Co., Ltd., average particle size 0.50 μm)

  As is apparent from Tables 3 to 6, the slurry for protective film prepared using the binder composition for an electricity storage device according to the present invention shown in Examples 17 to 38 is excellent in spinnability and has a crack rate. A low excellent protective film was given. Moreover, the electrical storage device (lithium ion battery) provided with the electrode with a protective film or the separator with a protective film had favorable charge / discharge rate characteristics.

  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.

Claims (11)

A water-soluble polymer (A);
At least one compound (B) selected from the group consisting of unsaturated carboxylic acids, unsaturated amides, and salts thereof;
A liquid medium (C);
Containing
The binder composition for an electricity storage device, wherein the proportion of repeating units derived from (meth) acrylamide contained in 100 parts by mass of the water-soluble polymer (A) is 40 to 100 parts by mass.   The binder composition for electrical storage devices of Claim 1 which contains 0.01-0.5 mass part of said compounds (B) with respect to 100 mass parts of said water-soluble polymers (A).   The water-soluble polymer (A) is a repeating unit derived from at least one selected from the group consisting of an acid having a polymerizable unsaturated double bond, an unsaturated carboxylic acid ester, and an α, β-unsaturated nitrile compound. The binder composition for an electricity storage device according to claim 1 or 2, further comprising:   The acid having a polymerizable unsaturated double bond is at least one selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, vinyl sulfonic acid, allyl sulfonic acid, and methallyl sulfonic acid. 2. The binder composition for an electricity storage device according to 1.   The slurry for electrical storage devices containing the binder composition for electrical storage devices as described in any one of Claims 1 thru | or 4, and an active material.   The slurry for electrical storage devices containing the binder composition for electrical storage devices as described in any one of Claims 1 thru | or 4, and a filler.   The slurry for an electricity storage device according to claim 6, wherein the filler is at least one particle selected from the group consisting of silica, titanium oxide, aluminum oxide, zirconium oxide, and magnesium oxide.   An electricity storage device electrode comprising: a current collector; and a layer formed by applying and drying the slurry for an electricity storage device according to claim 5 on a surface of the current collector. A current collector, and an active material layer formed on the surface of the current collector,
The electrical storage device electrode further provided with the layer formed by apply | coating and drying the slurry for electrical storage devices of Claim 6 or Claim 7 on the surface of the said active material layer.   The separator which equips the surface with the layer formed by apply | coating and drying the slurry for electrical storage devices of Claim 6 or Claim 7.   An electricity storage device comprising at least one of the electricity storage device electrode according to claim 8 or claim 9 and the separator according to claim 10.