JP2016143553A - Slurry for power storage device electrode, power storage device electrode, and power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a slurry for a power storage device electrode capable of manufacturing a power storage device electrode with excellent adhesion and charge-discharge characteristics.SOLUTION: A slurry for a power storage device electrode according to the present invention contains (A) a silicon material and (B) a carbon material as an active material. The slurry further contains (C) a graphene derivative and (D) a liquid medium.SELECTED DRAWING: None

Description

  The present invention relates to a slurry for an electricity storage device electrode, an electricity storage device electrode, and an electricity storage device.

  In recent years, a power storage device having a high voltage and a high energy density has been required as a power source for driving electronic devices. As such an electricity storage device, a lithium ion battery, a lithium ion capacitor, and the like are expected.

  An electrode used for such an electricity storage device is usually produced by applying and drying a composition (electrode slurry) containing an active material and a polymer functioning as a binder on the surface of the current collector. The The properties required for the polymer used as the binder include the ability to bond between active materials and the adhesion between the active material and the current collector, the abrasion resistance in the process of winding the electrode, and subsequent cutting, etc. An example is powder resistance that prevents fine powders of the active material from falling off from the applied and dried composition coating (hereinafter also referred to as “active material layer”). When the polymer satisfies these various required characteristics, the degree of freedom in structural design of the electricity storage device such as the method of folding the obtained electrode and setting the winding radius is increased, and the device can be miniaturized. it can.

  In addition, it has been empirically clarified that the quality of the active materials is substantially proportional to the ability to bond the active materials to each other, the ability to adhere the active material to the current collector, and the powder-off resistance. Therefore, in the present specification, hereinafter, the term “adhesiveness” may be used in a comprehensive manner.

  Recently, studies have been made to use a material having a large lithium occlusion amount from the viewpoint of achieving the demand for higher output and higher energy density of an electricity storage device. For example, an approach to improve the lithium occlusion amount by using graphite having higher crystallinity as an active material and to realize a capacity close to the theoretical occlusion amount (about 370 mAh / g) of the carbon material is being advanced. . On the other hand, Patent Document 1 discloses an approach in which a silicon material having a maximum lithium occlusion amount of about 4,200 mAh / g is used as an active material. In any case, it is considered that the capacity of the electricity storage device is greatly improved by utilizing such an active material having a large lithium storage amount.

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

  In addition, when a positive electrode active material layer is included, a conductive additive and a binder are included, which causes a reduction in discharge capacity per weight of the positive electrode active material layer. Studies have been made to reduce the amounts of the conductive assistant and the binder by using multilayer graphene having a function as the conductive assistant and the binder (see, for example, Patent Document 2).

  Furthermore, in order to obtain a high-output power storage device by increasing the contact area between the positive electrode active material and the electrolytic solution, a graphene oxide and a compound containing lithium and oxygen are used. Studies have been made to produce a positive electrode active material layer having graphene oxide in the gap (see, for example, Patent Document 3).

JP 2004-185810 A JP 2013-93319 A JP 2013-65551 A

  However, the electrode binder as described in Patent Document 1 has insufficient adhesion to put an active material using a material having a large amount of lithium occlusion into practical use, and the electrode deteriorates due to repeated charge and discharge. Therefore, there is a problem that the durability required for practical use cannot be obtained sufficiently.

  On the other hand, in the positive electrode active material layer described in Patent Document 2 and Patent Document 3, the adhesion is likely to be insufficient, and the electrode deteriorates due to repeated charge and discharge, so that the durability required for practical use is sufficiently high. There was a problem that it could not be obtained.

  Some embodiments according to the present invention provide a slurry for an electricity storage device electrode capable of producing an electricity storage device electrode having good adhesion and charge / discharge characteristics.

  Furthermore, some embodiments according to the present invention provide an electricity storage device electrode having good adhesion and charge / discharge characteristics, and an electricity storage device including the same.

  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 slurry for the electricity storage device electrode according to the present invention is:
Containing (A) silicon material and (B) carbon material as active materials,
Furthermore, (C) a graphene derivative and (D) a liquid medium are contained.

[Application Example 2]
In the slurry for the electricity storage device electrode of Application Example 1,
0.001-20 mass parts of said (C) graphene derivatives can be contained with respect to a total of 100 mass parts of said (A) silicon material and said (B) carbon material.

[Application Example 3]
In the slurry for the electricity storage device electrode of Application Example 1 or Application Example 2,
When the total amount of the (A) silicon material and the (B) carbon material is 100% by mass, the silicon material (A) can be contained in an amount of 1 to 50% by mass.

[Application Example 4]
In the slurry for the electricity storage device electrode of any one of Application Examples 1 to 3,
The (C) graphene derivative may be graphene oxide.

[Application Example 5]
In the slurry for the electricity storage device electrode of any one of Application Examples 1 to 4,
(E) A polymer can be further contained.

[Application Example 6]
In the slurry for the electricity storage device electrode of any one of Application Examples 1 to 5,
The polymer (E) is a repeating unit derived from a conjugated diene compound, a repeating unit derived from an aromatic vinyl compound, a repeating unit derived from an unsaturated carboxylic acid ester, and a repeating unit derived from an unsaturated carboxylic acid. And a diene polymer.

[Application Example 7]
In the slurry for the electricity storage device electrode of Application Example 5,
The (E) polymer may be a fluorine-containing polymer containing a repeating unit derived from a fluorine-containing ethylene monomer and a repeating unit derived from an unsaturated carboxylic acid ester.

[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 slurry for an electricity storage device electrode of any one of application examples 1 to 7 on the surface of the current collector.

[Application Example 9]
One aspect of the electricity storage device according to the present invention is:
The power storage device electrode according to Application Example 8 is provided.

  According to the slurry for an electricity storage device electrode according to the present invention, an electricity storage device electrode excellent in adhesion and charge / discharge characteristics can be produced.

  Furthermore, according to the electricity storage device electrode according to the present invention, the current collector and the active material layer containing the silicon material and the carbon material are excellent in adhesion capability, the active material layer is excellent in powder-off property, and the electricity The characteristics are also good. Moreover, according to the electrical storage device provided with such an electrical storage device electrode, the charge / discharge cycle characteristics, which is one of the electrical characteristics, are particularly good.

It is sectional drawing which shows typically the electrical storage device electrode which concerns on this embodiment.

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

1. Storage Device Electrode Slurry The storage device electrode slurry according to the present embodiment contains (A) a silicon material and (B) a carbon material as active materials, and further contains (C) a graphene derivative and (D) a liquid medium. It is characterized by that. The slurry for the electricity storage device electrode is a dispersion used for forming an active material layer on the surface of the current collector by applying it to the surface of the current collector and then drying it. Hereafter, each component contained in the slurry for electrical storage device electrodes which concerns on this embodiment is demonstrated in detail.

1.1. Active Material The electricity storage device electrode slurry according to the present embodiment contains (A) a silicon material and (B) a carbon material as active materials. The slurry for an electricity storage device electrode according to the present embodiment can be used for the purpose of producing an active material layer of either the positive electrode or the negative electrode, but the (A) silicon material having a large lithium occlusion amount and ( B) Since it contains a carbon material as an active material, it is particularly suitable for use in producing a negative electrode.

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

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

  (A) Since the silicon material has a larger amount of occlusion of lithium per unit weight than other active materials, the storage capacity of the resulting electricity storage device can be increased by containing (A) the silicon material as the active material. As a result, the output and energy density of the electricity storage device can be increased. On the other hand, since (B) the carbon material has a small volume change due to charge / discharge, by using a mixture of (A) silicon material and (B) carbon material as the active material, (A) volume change of the silicon material Can be mitigated, and the adhesion ability between the current collector and the active material layer can be further improved. As such a mixture, a carbon-coated silicon material in which a film of (B) a carbon material is formed on the surface of (A) a silicon material can also be used. By using a carbon-coated silicon material, (A) the influence of volume change associated with charging / discharging of the silicon material can be more effectively mitigated by the (B) carbon material existing on the surface. It becomes easy to further improve the adhesion between the body and the active material layer.

When silicon (Si) is used as an active material, silicon can occlude up to 22 lithium atoms per 5 atoms (5Si + 22Li → Li ₂₂ Si ₅ ). As a result, the theoretical silicon capacity reaches 4200 mAh / g. However, silicon causes a large volume change when occludes lithium. Specifically, the carbon material expands in volume up to about 1.2 times by occluding lithium, whereas the silicon material expands in volume up to about 4.4 times by occluding lithium. For this reason, the silicon material is pulverized by repeated expansion and contraction, peeling from the current collector, and separation of the active materials, and the conductive network inside the active material layer is broken. Therefore, the cycle characteristics are extremely deteriorated in a short time. However, the electricity storage device electrode having an active material layer produced using the electricity storage device electrode slurry according to the present embodiment can exhibit good electrical characteristics without causing the above-described problems.

  When the total amount of (A) silicon material and (B) carbon material contained as the active material is 100% by mass, the content ratio of (A) silicon material may be 1% by mass or more and 50% by mass or less. It is preferably 5% by mass or more and 45% by mass or less, more preferably 10% by mass or more and 40% by mass or less. (A) When the content ratio of the silicon material is within the above range, the volume expansion of (B) the carbon material relative to the volume expansion of (A) the silicon material accompanying the occlusion of lithium is small. Volume change accompanying charging / discharging of the material layer can be reduced, and adhesion between the current collector and the active material layer can be further improved.

The slurry for an electricity storage device electrode according to the present embodiment may contain an active material other than the above, for example, an oxide containing a lithium atom, a lead compound, a tin compound, an arsenic compound, an antimony compound, an aluminum compound, and the like. 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. 0.05} Fe _0.30 Co _0.30 Mn _0.30 PO ₄ or the like.

Moreover, the slurry for an electricity storage device electrode according to this embodiment may contain an active material exemplified below. Examples of such an active material include a conductive polymer such as polyacene; A _X B _Y O _Z (where A is an alkali metal or transition metal, B is a transition metal such as cobalt, nickel, aluminum, tin, or manganese) At least one selected, O represents an oxygen atom, and X, Y, and Z are 1.10>X> 0.05, 4.00>Y> 0.85, 5.00>Z> 1.5, respectively. The composite metal oxide represented by (2) and other metal oxides are exemplified.

  The shape of the active material is not particularly limited, but is preferably granular. The average particle diameter of the active material is preferably 0.1 to 100 μm, and more preferably 1 to 20 μm.

  Here, the average particle diameter of the active material is a volume average particle diameter calculated from a particle size distribution measured by using a particle size distribution measuring apparatus based on a laser diffraction method. Examples of such a laser diffraction particle size distribution measuring apparatus include HORIBA LA-300 series, HORIBA LA-920 series (manufactured by Horiba, Ltd.) and the like. This particle size distribution measuring apparatus does not only evaluate primary particles of the active material, but also evaluates secondary particles formed by aggregation of the primary particles. Therefore, the average particle diameter obtained by this particle size distribution measuring apparatus can be used as an index of the dispersion state of the active material contained in the slurry for the electricity storage device electrode. The average particle diameter of the active material can also be measured by centrifuging the slurry to settle the active material, removing the supernatant, and measuring the precipitated active material by the above method. .

  When the slurry for an electricity storage device electrode according to this embodiment contains the (E) polymer described later, the content ratio of the active material is 0.1 (E) polymer with respect to 100 parts by mass of the active material. It is preferable to use it at a ratio of ˜25 parts by mass, and it is more preferable to use it at a ratio of 0.5 to 15 parts by mass. By setting it as such a content rate, the electrical storage device electrode which was excellent by adhesiveness and also excellent in charging / discharging characteristics with small electrode resistance can be manufactured.

1.2. (C) Graphene Derivative The slurry for an electricity storage device electrode according to the present embodiment contains (C) a graphene derivative. The “graphene derivative” in the present specification refers to a compound obtained by chemically modifying graphene, and examples thereof include those obtained by adding fluorine, nitrogen, organic groups, and the like.

  Examples of (C) graphene derivatives include graphene oxide and graphane. Among these, graphene oxide is particularly preferable from the viewpoints of the adhesion ability between the current collector and the active material layer, the powder-off property of the active material layer, and the electrical characteristics. (C) The reason why the charge / discharge characteristics of the electricity storage device are improved by adding the graphene derivative is not clear, but is considered as follows. First, by adding the (C) graphene derivative, the hardness of the obtained active material layer is increased, but at the same time, toughness is imparted. Such a reinforcing effect is considered to contribute to the charge / discharge cycle characteristics. Secondly, since the sheet of (C) graphene derivative has a very wide specific surface area, the presence of electron conduction increases the double layer capacity in contact with the electrolyte. Thereby, it is considered that an electricity storage device having a large discharge capacity and good characteristics can be obtained.

Graphene oxide has a carbon-sp ² bonded portion (that is, benzene is bonded two-dimensionally) (sp ² bonded portion) and an oxygen functional group (sp ³ bonded portion). This oxygen functional group is composed of an epoxy group (COC), a hydroxy group (COH), a carbonyl group (CO), and a carboxy group (COOH). Thus, since graphene oxide has an insulating and hydrophilic sp ³ bond portion on the surface, it can be dispersed in water and a uniform slurry for an electricity storage device electrode can be obtained.

The graphene oxide is preferably in the form of a sheet. The size of the sheet is preferably 1 nm to 100 μm, and more preferably 5 nm to 80 nm. Further, the graphene oxide sheet may be formed of only a single atomic layer of the sp ² bonding portion, or a plurality of the single layers may be stacked. When a plurality of sp ² bonding portions are laminated, the number of layers from 1 to 70 is preferably 70% or more, more preferably 75% or more.

  As a method for synthesizing graphene oxide, the Brodie method, the Staudenmaier method, the Hummers method, and the like are known, and among them, the Hummers method is preferable from the viewpoint of safety. The Hummers method is a method of synthesizing graphene oxide by adding potassium permanganate to graphite, sodium nitrate, and sulfuric acid.

  The ratio of the number of atoms of carbon (C) and oxygen (O) in graphene oxide (C / O) is preferably 20/80 to 98/2, and the adhesion ability between the current collector and the active material layer, From the viewpoints of the powderability and electrical characteristics of the active material layer, it is more preferably 30/70 to 95/5.

  The ratio of the number of oxygen atoms can be evaluated by conducting surface elemental composition analysis by ESCA (XPS) method using Quantum 2000 (manufactured by ULVAC-PHI).

  Examples of such graphene oxide include single-layer graphene oxide, and single-layer graphene oxide G-17A (EM Japan Co., Ltd.) is commercially available.

  The content ratio of the (C) graphene derivative in the slurry for the electricity storage device electrode according to this embodiment is from the viewpoint of the adhesion ability between the current collector and the active material layer, the powderability of the active material layer, and the electrical characteristics ( It is preferable that it is 0.001-20 mass parts with respect to a total of 100 mass parts of A) silicon material and the said (B) carbon material, It is more preferable that it is 0.005-15 mass parts, 0.01 It is particularly preferably 10 to 10 parts by mass.

1.3. (D) Liquid medium The slurry for an electricity storage device electrode according to this embodiment contains (D) a liquid medium. (D)
The liquid medium is preferably an aqueous medium containing water. The aqueous medium can contain a non-aqueous medium other than water. Examples of the non-aqueous medium include amide compounds such as N-methylpyrrolidone, dimethylformamide, and N, N-dimethylacetamide; hydrocarbons such as toluene, xylene, n-dodecane, and tetralin; 2-ethyl-1-hexanol; Alcohols such as 1-nonanol and lauryl alcohol; ketones such as methyl ethyl ketone, cyclohexanone, phorone, acetophenone and isophorone; esters such as benzyl acetate, isopentyl butyrate, methyl lactate, ethyl lactate and butyl lactate; o-toluidine, m-toluidine, p -Amine compounds such as toluidine; lactones such as γ-butyrolactone and δ-butyrolactone; sulfoxides and sulfone compounds such as dimethyl sulfoxide and sulfolane, and one or more selected from these can be used. be able to.

  (D) When the liquid medium is an aqueous medium, 90% by mass or more is preferably water, more preferably 98% by mass or more is water, and 100% by mass is 100% by mass of the total amount of the liquid medium. Particularly preferred is water. In the slurry for an electricity storage device electrode according to the present embodiment, (D) by using an aqueous medium as a liquid medium, the degree of adverse effects on the environment is reduced, and the safety for handling workers is also increased.

1.4. Other Additives In addition to the components described above, other components may be added to the slurry for the electricity storage device electrode according to the present embodiment as necessary. Examples of such components include (E) a polymer, a conductive aid, a thickener, and the like.

1.4.1. (E) Polymer The slurry for an electricity storage device electrode according to the present embodiment is (E) heavy from the viewpoint of improving the binding property between active materials, the adhesion between the active material and the current collector, and the powder fall resistance. It is preferable to contain a coalescence. When (E) a polymer is contained, it is preferably in a latex form in which (D) particles of the polymer (E) are dispersed in a liquid medium. It is preferable that the slurry for the electricity storage device electrode according to the present embodiment is in a latex form because not only the stability is improved but also the coating property is improved.

  As described above, the slurry for an electricity storage device electrode according to this embodiment can also be used for producing an active material layer of either the positive electrode or the negative electrode. When the slurry for an electricity storage device electrode according to this embodiment is used for producing a negative electrode active material layer, the (E) polymer is preferably the following diene polymer. When the slurry for an electricity storage device electrode according to the present embodiment is used to produce a positive electrode active material layer, the polymer (E) has the following fluorine-containing heavy weight from the viewpoint of being excellent in both oxidation resistance and adhesion. It is preferably a coalescence. Moreover, (E) polymer contained in the slurry for electrical storage device electrodes which concerns on this embodiment may contain at least 1 sort (s) selected from the group which consists of polyamic acid and its imidation polymer.

  The content ratio of the (C) graphene derivative in the electricity storage device electrode slurry according to the present embodiment is such that (E) 100 parts by mass of the polymer, the adhesion between the current collector and the active material layer, From the viewpoints of powder fallability and electrical characteristics, it is preferably 0.001 to 20 parts by mass, more preferably 0.002 to 15 parts by mass, and particularly preferably 0.005 to 10 parts by mass. preferable.

1.4.1.1. Diene Polymer The diene polymer is composed of a repeating unit (Ma) derived from a conjugated diene compound, a repeating unit (Mb) derived from an aromatic vinyl compound, and a repeating unit (Mc) derived from an unsaturated carboxylic acid ester. And a repeating unit (Md) derived from an unsaturated carboxylic acid.

<Repeating unit derived from conjugated diene compound (Ma)>
When the diene polymer has a repeating unit (Ma) derived from a conjugated diene compound, it becomes easy to produce a negative electrode binder excellent in viscoelasticity and strength. That is, when a polymer having a repeating unit derived from a conjugated diene compound is used, a strong binding force can be imparted to the polymer. When rubber elasticity derived from the conjugated diene compound is imparted to the polymer, it becomes possible to follow changes such as volume shrinkage and expansion of the electrode. Therefore, it is thought that it has the durability which improves a binding property and maintains a charge / discharge characteristic for a long term.

  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. Among these, 1,3-butadiene is particularly preferable.

  In the diene polymer, the content ratio of the repeating unit (Ma) derived from the conjugated diene compound is preferably 30 to 60 parts by mass when the total of all the repeating units is 100 parts by mass, and 40 to 55 parts by mass. More preferably, it is a part. When the content ratio of the repeating unit (Ma) in the diene polymer is in the above range, the binding property can be further improved.

<Repeating unit derived from aromatic vinyl compound (Mb)>
When the diene polymer has a repeating unit (Mb) derived from an aromatic vinyl compound, when the slurry for negative electrode contains (B) a carbon material, the affinity for this can be improved.

  Examples of the aromatic vinyl compound include styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, chlorostyrene, divinylbenzene, and the like, and can be one or more selected from these. . Among these, styrene is particularly preferable.

  In the diene polymer, the content ratio of the repeating unit (Mb) derived from the aromatic vinyl compound is preferably 10 to 40 parts by mass when the total of all the repeating units is 100 parts by mass. More preferably, it is part by mass. When the content ratio of the repeating unit (Mb) is within the above range, the polymer can impart appropriate binding properties to the graphite used as the (B) carbon material. In addition, the obtained electrode active material layer is excellent in flexibility and binding property to the current collector.

<Repeating unit derived from unsaturated carboxylic acid ester (Mc)>
When the diene polymer has a repeating unit (Mc) derived from an unsaturated carboxylic acid ester, the affinity with the electrolytic solution is improved, and the internal resistance due to the polymer becoming an electrical resistance component in the electricity storage device. While suppressing the rise, it is possible to prevent a decrease in binding property due to excessive absorption of the electrolytic solution.

The unsaturated carboxylic acid ester is preferably a (meth) acrylate compound. Specific examples of the (meth) acrylate compound include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, and (meth) acrylate n. -Butyl, i-butyl (meth) acrylate, n-amyl (meth) acrylate, i-amyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, (meth) acrylic acid 2 -Ethylhexyl, n-octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, hydroxymethyl (meth) acrylate, hydroxyethyl (meth) acrylate, ethylene glycol di (meth) acrylate , Propylene glycol di (meth) acrylate, trimethylol propylene tri (meth) acrylate , Tetra (meth) acrylate, pentaerythritol hexa (meth) acrylate dipentaerythritol can be mentioned (meth) allyl acrylate, can be at least one selected from among these. Among these, one or more selected from methyl (meth) acrylate, ethyl (meth) acrylate and 2-ethylhexyl (meth) acrylate is preferable, and methyl (meth) acrylate is particularly preferable. preferable.

  In the diene polymer, the content of the repeating unit (Mc) derived from the unsaturated carboxylic acid ester is preferably 5 to 40 parts by mass when the total of all the repeating units is 100 parts by mass. More preferably, it is 30 parts by mass. When the content ratio of the repeating unit (Mc) is within the above range, the diene polymer has an appropriate affinity with the electrolyte solution, and the internal resistance is increased due to the binder being an electrical resistance component in the electricity storage device. While suppressing, the fall of binding property by absorbing an electrolyte excessively can be prevented.

<Repeating unit derived from unsaturated carboxylic acid (Md)>
When the diene polymer has a repeating unit (Md) derived from an unsaturated carboxylic acid, the stability of the slurry for an electricity storage device electrode according to this embodiment is improved.

  Examples of the unsaturated carboxylic acid include mono- or dicarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, and one or more selected from these. Can do. Among these, it is preferable that it is 1 or more types selected from acrylic acid, methacrylic acid, and itaconic acid.

  In the diene polymer, the content of the repeating unit (Md) derived from the unsaturated carboxylic acid is preferably 15 parts by mass or less when the total of all the repeating units is 100 parts by mass. It is more preferable that it is 10 mass parts. When the content ratio of the repeating unit (Md) is in the above range, the stability of the diene polymer is improved during the preparation of the slurry for the electricity storage device electrode, and thus aggregates are hardly generated. Further, an increase in slurry viscosity over time can be suppressed.

<Other repeating units>
The diene polymer may have a repeating unit other than the above. Examples of the repeating unit other than the above include repeating units derived from α, β-unsaturated nitrile compounds.

  Examples of the α, β-unsaturated nitrile compound include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile, vinylidene cyanide, and the like. it can. Among these, at least one selected from acrylonitrile and methacrylonitrile is preferable, and acrylonitrile is more preferable.

  In the diene polymer, the content of the repeating unit derived from the α, β-unsaturated nitrile compound is preferably 35 parts by mass or less when the total of all the repeating units is 100 parts by mass. More preferably, it is 25 parts by mass. When the content ratio of the repeating unit derived from the α, β-unsaturated nitrile compound is in the above range, the compatibility with the electrolytic solution used in the electricity storage device is excellent, and the swelling rate is not excessively increased. It can contribute to improvement.

  In addition, the diene polymer may further have a repeating unit derived from the compound shown below. Examples of such compounds include fluorine-containing compounds having an ethylenically unsaturated bond such as vinylidene fluoride, ethylene tetrafluoride and hexafluoropropylene; ethylenically unsaturated carboxylic acids such as (meth) acrylamide and N-methylolacrylamide. Acid alkyl amides; Vinyl acetates, vinyl acetates, vinyl propionates, etc .; Acid anhydrides of ethylenically unsaturated dicarboxylic acids; Monoalkyl esters; Monoamides; Aminoethylacrylamide, dimethylaminomethylmethacrylamide, Methylaminopropylmethacrylamide Aminoalkylamides of ethylenically unsaturated carboxylic acids such as vinyl sulfonic acid, styrene sulfonic acid, allyl sulfonic acid, sulfoethyl methacrylate, sulfopropyl methacrylate, sulfobutyl methacrylate Examples include compounds having a sulfonic acid group such as 2-acrylamido-2-methylpropanesulfonic acid, 2-hydroxy-3-acrylamidopropanesulfonic acid, and 3-allyloxy-2-hydroxypropanesulfonic acid. It can be one or more selected from.

<Synthesis Method of Diene Polymer>
The method for synthesizing the diene polymer is not particularly limited, and for example, it can be produced by the method described in Japanese Patent No. 5146710.

1.4.1.2. Fluorine-containing polymer The fluorine-containing polymer preferably contains a repeating unit (Me) derived from a fluorine-containing ethylene monomer and a repeating unit (Mf) derived from an unsaturated carboxylic acid ester. By having the repeating unit (Me) derived from the fluorine-containing ethylene-based monomer, the (E) polymer can be imparted with oxidation resistance, but the adhesion and flexibility tend to be lowered. On the other hand, by having the repeating unit (Mf) derived from the unsaturated carboxylic acid ester, it is possible to impart adhesion and flexibility to the (E) polymer, but the oxidation resistance tends to be low. Therefore, if it is a fluorine-containing polymer having a repeating unit (Me) derived from a fluorine-containing ethylene monomer and a repeating unit (Mf) derived from an unsaturated carboxylic acid ester, the respective drawbacks are compensated. It is possible to exhibit adhesion and flexibility without deteriorating oxidation resistance. Since the above-mentioned diene polymer has low oxidation resistance, a fluorine-containing polymer can be suitably used as a positive electrode binder in a positive electrode that requires stability against a high potential.

<Repeating unit derived from fluorine-containing ethylene monomer (Me)>
When the fluorine-containing polymer has a repeating unit (Me) derived from a fluorine-containing ethylene monomer, oxidation resistance can be imparted to the fluorine-containing polymer.

（一般式（１）中、Ｒ^１は水素原子またはメチル基であり、Ｒ^２はフッ素原子を含有する炭素数１〜１８の炭化水素基である。） Examples of the fluorine-containing ethylene monomer include olefin compounds having fluorine atoms and (meth) acrylate compounds having fluorine atoms. Examples of the olefin compound having a fluorine atom include vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, ethylene trifluoride chloride, and perfluoroalkyl vinyl ether. As the (meth) acrylate compound having a fluorine atom, for example, a compound represented by the following general formula (1), (meth) acrylic acid 3 [4 [1-trifluoromethyl-2,2-bis [bis (trifluoro) Methyl) fluoromethyl] ethynyloxy] benzooxy] 2-hydroxypropyl and the like.

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

Examples of R ² in the general formula (1) include a fluorinated alkyl group having 1 to 12 carbon atoms, a fluorinated aryl group having 6 to 16 carbon atoms, and a fluorinated aralkyl group having 7 to 18 carbon atoms. Of these, a fluorinated alkyl group having 1 to 12 carbon atoms is preferable. Preferable specific examples of R ^{2 in} the general formula (1) include, for example, 2,2,2-trifluoroethyl group, 2,2,3,3,3-pentafluoropropyl group, 1,1,1, 3,3,3-hexafluoropropan-2-yl group, β- (perfluorooctyl) ethyl group, 2,2,3,3-tetrafluoropropyl group, 2,2,3,4,4,4- Hexafluorobutyl group, 1H, 1H, 5H-octafluoropentyl group, 1H, 1H, 9H-perfluoro-1-nonyl group, 1H, 1H, 11H-perfluoroundecyl group, perfluorooctyl group and the like can be mentioned. .

  Of these, the fluorine-containing ethylene monomer is preferably an olefin compound having a fluorine atom, and is at least one selected from the group consisting of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene. More preferred. Said fluorine-containing ethylene-type monomer may be used individually by 1 type, and 2 or more types may be mixed and used for it.

  In the fluorinated polymer, the content of the repeating unit (Me) derived from the fluorinated ethylene monomer is preferably 20 to 40 parts by mass when the total of all the repeating units is 100 parts by mass. It is more preferable that it is 25-35 mass parts.

<Repeating unit derived from unsaturated carboxylic acid ester (Mf)>
When the fluorine-containing polymer has a repeating unit (Mf) derived from an unsaturated carboxylic acid ester, adhesion and flexibility can be imparted to the fluorine-containing polymer particles.

  The unsaturated carboxylic acid ester is preferably a (meth) acrylate compound. Specific examples of the (meth) acrylate compound include the compounds exemplified in <Repeating unit (Mc) derived from unsaturated carboxylic acid ester> of the diene polymer.

  In the fluorine-containing polymer, the content of the repeating unit (Mf) derived from the unsaturated carboxylic acid ester is preferably 45 to 80 parts by mass when the total of all the repeating units is 100 parts by mass, and 50 More preferably, it is -70 mass parts.

  The fluorine-containing polymer may have a repeating unit other than the above. Examples of the repeating unit other than the above include the repeating unit derived from an unsaturated carboxylic acid and the repeating unit derived from an α, β-unsaturated nitrile compound described in the diene polymer.

<Method for synthesizing fluorine-containing polymer>
The method for synthesizing the fluorine-containing polymer is not particularly limited, but for example, it can be produced by the method described in Japanese Patent No. 4849286.

1.4.1.3. Polyamic acid and its imidized polymer The (E) polymer contained in the slurry for electrical storage device electrodes according to this embodiment contains at least one selected from the group consisting of a polyamic acid and its imidized polymer. Also good. A polyamic acid is obtained by reacting a tetracarboxylic dianhydride and a diamine. The partially imidized product of polyamic acid can be obtained by dehydrating and ring-closing a part of the amic acid structure of the polyamic acid to imidize it.

  As the tetracarboxylic dianhydride and diamine used for synthesizing the polyamic acid, the tetracarboxylic dianhydrides and diamines described in JP 2010-97188 A can be used. Polyamic acid and its imidized polymer can be synthesized by the method described in Japanese Patent No. 5099394.

1.4.1.4. (E) Physical properties of polymer <average particle size>
(E) When a polymer is particle | grains, it is preferable that the average particle diameter of the said polymer particle exists in the range of 50-500 nm, and it is more preferable that it exists in the range of 100-300 nm. When the average particle diameter of the polymer particles is within the above range, the polymer particles are effectively adsorbed onto the surface of the active material, so that the binding property between the active materials is improved. In addition, since the polymer particles can move following the movement of the active material, it is possible to suppress only one of both particles from migrating alone, and the electrical characteristics of the electrode are deteriorated. Can be suppressed.

  The average particle diameter of the polymer particles can be measured in accordance with JIS Z 8826 using a particle size distribution measuring apparatus based on the dynamic light scattering method. Examples of such a particle size distribution measuring apparatus include Coulter LS230, LS100, LS13320 (above, manufactured by Beckman Coulter. Inc), ALV5000 (manufactured by ALV), FPAR-1000 (manufactured by Otsuka Electronics Co., Ltd.), and the like. Can do.

<Tetrahydrofuran (THF) insoluble matter>
(E) The THF-insoluble content of the polymer is preferably 80% by mass or more, and more preferably 90% by mass or more. It has been empirically confirmed that this THF insoluble matter is approximately proportional to the amount of insoluble matter with respect to the electrolyte used in the electricity storage device. For this reason, by manufacturing an electricity storage device using the (E) polymer having a THF-insoluble content within the above range, the elution of the (E) polymer into the electrolyte even when charging and discharging are repeated over a long period of time. Can be suppressed.

(E) The THF-insoluble content of the polymer can be determined as follows. First, about 10 g of latex containing (E) polymer particles is weighed into a Teflon (registered trademark) petri dish having a diameter of 8 cm and dried at 120 ° C. for 1 hour to form a film. 1 g of the obtained membrane (polymer) is immersed in 400 mL of THF and shaken at 50 ° C. for 3 hours. Next, the THF phase was filtered through a 300-mesh wire mesh to separate insoluble matters, and the weight (Y (g)) of the residue obtained by evaporating and removing the dissolved THF was measured. 2) Determine the amount of THF unnecessary.
THF insoluble matter (%) = ((1-Y) / 1) × 100 (2)

<Glass transition temperature>
(E) The polymer preferably has only one endothermic peak in the temperature range of −50 to + 50 ° C. when measured by differential scanning calorimetry (DSC) according to JIS K 7121. . The temperature of this endothermic peak (glass transition temperature (Tg)) is −4
More preferably, it is in the range of 0 to + 30 ° C, and more preferably -30 to + 20 ° C. When there is only one endothermic peak of the (E) polymer in the DSC analysis and the peak temperature is within the above range, the ((E) polymer exhibits good adhesion and the active material layer It is preferable because better flexibility and tackiness can be imparted.

1.4.2. Conductive aid Specific examples of the conductive aid include carbon and the like (except for (C) graphene derivatives) in lithium ion secondary batteries. Examples of carbon include activated carbon, acetylene black, ketjen black, furnace black, graphite, carbon fiber, and fullerene. Among these, acetylene black and furnace black can be preferably used. The use ratio of the conductive auxiliary agent is preferably 20 parts by mass or less, more preferably 1 to 15 parts by mass, and particularly preferably 2 to 10 parts by mass with respect to 100 parts by mass of the active material. .

1.4.3. Thickener The slurry for an electricity storage device electrode according to the present embodiment can further improve its applicability, charge / discharge characteristics of the obtained electricity storage device, and the like by containing a thickener.

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

  Examples of commercially available thickeners include alkali metal salts of carboxymethyl cellulose such as CMC1120, CMC1150, CMC2200, CMC2280, and CMC2450 (manufactured by Daicel Corporation).

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

1.5. Manufacturing method of slurry for electricity storage device electrode The slurry for electricity storage device electrode according to this embodiment includes an active material (including (A) silicon material and (B) carbon material), (C) graphene derivative, and (D). It can manufacture by mixing a liquid medium and the additive used as needed. These can be mixed by stirring by a known method. For example, a stirrer, a defoaming machine, a bead mill, a high-pressure homogenizer, or the like can be used.

  As mixing and stirring for producing a slurry for an electricity storage device electrode, it is necessary to select a mixer that can stir to such an extent that no agglomerates of active material remain in the slurry and, if necessary, sufficient dispersion conditions. The degree of dispersion can be measured with 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. Storage Device Electrode Hereinafter, the storage device electrode according to the present embodiment will be described with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing an electricity storage device electrode 100 (hereinafter also simply referred to as “electrode”) according to the present embodiment. As shown in FIG. 1, the electrode 100 includes a current collector 10 and an active material layer 20 formed on the surface of the current collector 10. The active material layer 20 is a layer formed on the surface of the current collector 10 by applying and drying the above slurry for an electricity storage device electrode. In the electrode 100, the slurry is applied to the surface of an appropriate current collector 10 such as a metal foil to form a coating film, and then the liquid medium is dried and removed from the coating film to form the active material layer 20. Can be manufactured. The electrode 100 manufactured in this manner has the above-described (A) silicon material, (B) carbon material, and (C) graphene derivative, and optional additional components used as necessary on the current collector 10. The active material layer 20 to be contained is bound. The electrode 100 is excellent in the adhesion ability between the current collector 10 and the active material layer 20 and has good charge / discharge cycle characteristics, which is one of the electrical characteristics. Further, it is a good electrode in which the active material is prevented from peeling off, and is excellent in that the change in electrode film thickness after charging is small.

  The material of the current collector 10 is not particularly limited as long as it is made of a conductive material. In a lithium ion secondary battery, a current collector made of metal such as iron, copper, aluminum, nickel, and stainless steel is used. In particular, when aluminum is used for the positive electrode and copper is used for the negative electrode, the above-described effects are obtained. Appears most often. 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. Although the shape and thickness of the current collector 10 are not particularly limited, it is preferable to have a sheet-like shape having a thickness of about 0.001 to 0.5 mm.

  The thickness of the active material layer 20 is not particularly limited, but is usually 0.005 to 5 mm, preferably 0.01 to 2 mm. In the power storage device electrode 100 in FIG. 1, the active material layer 20 is formed only on one surface of the current collector 10, but the active material layer 20 may be formed on both surfaces of the current collector 10. .

  There is no particular limitation on the method of applying the slurry to the current collector 10. 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 slurry is not particularly limited, but the thickness of the active material layer formed after removing the liquid medium is preferably 0.005 to 5 mm, and preferably 0.01 to 2 mm. More preferably.

  The method for drying and removing the liquid medium from the coated film after coating is not particularly limited, for example, drying with warm air, hot air, low-humidity air; vacuum drying; (far) drying by irradiation with infrared rays, electron beams, etc. Can do. 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.

  It is preferable to increase the density of the active material layer by further pressing the coating film after removing the liquid medium. Examples of the pressing method include a mold press and a roll press. The press conditions should be set appropriately depending on the type of press equipment used and the desired 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 0.5 to 5 t. For example, when the roll temperature is 20 to 100 ° C. at a pressure of 50 cm / cm, the feeding speed of the coating film after removing the liquid medium (rotation speed of the roll) is 1 to 80 m / min, preferably 5 to 50 m / min. it can.

  It is preferable that the pressed coating film is further heated under reduced pressure to completely remove the liquid medium. In this case, the degree of reduced pressure is preferably 50 to 200 Pa, more preferably 75 to 150 Pa as an absolute pressure. As heating temperature, it is preferable to set it as 100-200 degreeC, and it is more preferable to set it as 120-180 degreeC. The heating time is preferably 2 to 12 hours, and more preferably 4 to 8 hours.

  The electricity storage device electrode manufactured in this way is excellent in the adhesion capability between the current collector and the active material layer, and has good charge / discharge characteristics.

  In the electricity storage device electrode according to the present embodiment, when a silicon material is used as the active material, the content ratio of the silicon element in 100% by mass of the active material layer is preferably 1 to 50% by mass, and 2 to 40% by mass. More preferably, it is 3 to 30% by mass. When the content of the silicon element in the active material layer is within the above range, an active material layer having a uniform silicon element distribution can be obtained in addition to an improvement in the storage capacity of an electricity storage device manufactured using the active material layer.

The content of silicon element in the active material layer in the present invention can be measured by the following procedure. That is,
(1) Using a fluorescent X-ray analyzer (product name “Panalytic MagixPRO” manufactured by Spectris Co., Ltd.), a plurality of samples prepared in advance with a known silicon element content are measured, and a calibration curve is created.
(2) 3 g of the entire active material layer (not to collect only a part in the depth direction) is scraped from the power storage device electrode with a spatula or the like, and mixed with a mortar or the like so that the whole becomes uniform. Press into a disk-shaped plate. If the active material layer alone cannot be formed, an adhesive having a known elemental composition may be used as appropriate. As such an adhesive, for example, styrene / maleic acid resin, boric acid powder, cellulose powder and the like can be used. Further, even when the silicon content is high and the linearity of the calibration curve cannot be ensured, the sample can be diluted and measured using the adhesive. In addition, when using the said adhesive agent, in order to avoid the shift | offset | difference of the calibration curve by a matrix effect, it is preferable to similarly use an adhesive agent also for the calibration curve preparation sample.
(3) The obtained plate is set in a fluorescent X-ray analyzer and analyzed, and the silicon element content is calculated from the calibration curve. When the above adhesive is used, the silicon element content is calculated after subtracting the weight of the adhesive.

3. Power Storage Device The power storage device according to the present embodiment includes the above-described power storage device electrode, and further contains an electrolytic solution and can be manufactured according to a conventional method using components such as a separator. As a specific manufacturing method, for example, a negative electrode and a positive electrode are overlapped via a separator, and this is wound or folded according to the shape of the battery, and stored in a battery container, and an electrolytic solution is injected into the battery container. Can be mentioned. The shape of the battery can be an appropriate shape such as a coin shape, a cylindrical shape, a square shape, or a laminate 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 , Li
AlCl 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, lower fatty acid lithium carboxylate, etc. It can be illustrated. In a nickel metal hydride secondary battery, for example, an aqueous potassium hydroxide solution having a conventionally known concentration of 5 mol / liter or more can be used.

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

4). 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.

4.1. Example 1
4.1.1. (E) Synthesis and Evaluation of Polymer Particles <(E) Synthesis of Polymer Particles>
In a temperature-controllable autoclave equipped with a stirrer, 300 parts by weight of water, 0.6 parts by weight of sodium dodecylbenzenesulfonate, 1.0 part by weight of potassium persulfate, 0.5 part by weight of sodium bisulfite, α-methylstyrene 0.2 parts by weight of dimer, 0.2 parts by weight of dodecyl mercaptan, and 72 parts by weight of 1,3-butadiene, 7 parts by weight of styrene, 10 parts by weight of methyl methacrylate, which are the polymerization monomer components shown in Table 1. 5 parts by mass of acrylonitrile, 3 parts by mass of 2-hydroxyethyl methacrylate, 2 parts by mass of acrylic acid, and 1 part by mass of itaconic acid were sequentially charged, and a polymerization reaction was performed at 70 ° C. for 8 hours. When 3 hours passed from the start of addition of the polymerization monomer component, 1.0 part by mass of α-methylstyrene dimer and 0.3 part by mass of dodecyl mercaptan were further added. Thereafter, the temperature in the autoclave was raised to 80 ° C., and further reacted for 2 hours to obtain a latex. Thereafter, the pH of the latex was adjusted to 7.0, and 5 parts by mass of sodium tripolyphosphate (added as an aqueous solution having a solid content conversion value and a concentration of 10% by mass) was added. Subsequently, the residual monomer was removed by steam distillation, and concentrated under reduced pressure to obtain an aqueous dispersion containing 35% by mass of (E) polymer particles.

<Measurement of average particle diameter>
The particle size distribution of the aqueous dispersion obtained above is measured using a particle size distribution measuring apparatus (model “FPAR-1000”, manufactured by Otsuka Electronics Co., Ltd.) using the dynamic light scattering method as a measurement principle, and the particle size distribution is obtained. From this, the average particle diameter (D50) was determined to be 150 nm.

<DSC analysis>
When the (E) polymer particles were separated from the aqueous dispersion obtained above, and the (E) polymer particles were measured with a differential scanning calorimeter (DSC) in accordance with JIS K7121, a single glass was obtained. Only one transition temperature (Tg) was observed at -60 ° C.

4.1.2. Preparation and Evaluation of Storage Device Electrode Slurry <Preparation of Storage Device Composition>
10.1 g of an aqueous suspension containing 1% of 5-chloro-2-methyl-4-isothiazolin-3-one was added to 1000 g of the aqueous dispersion containing the polymer (E) obtained above, and 300 rpm The composition for electrical storage devices was prepared by stirring by.

  In addition, content of 5-chloro-2-methyl-4-isothiazolin-3-one in the composition for electrical storage devices can be confirmed by analyzing the binder composition according to the following procedure. That is, 2.0 g of the obtained composition for an electricity storage device is weighed, and an aqueous aluminum sulfate solution is added to cause aggregation. Next, the agglomerated polymer component is filtered, and a high-performance liquid chromatography apparatus (column: manufactured by Waters, μBondasphere 5μ C18-100Å (inner diameter: 3.9 mm, length: 150 mm), mobile phase: using distilled water. Trifluoroacetic acid was added to 2 L of the prepared 0.01 M ammonium acetate, pH was adjusted to 4.0, 500 mL of acetonitrile for high performance liquid chromatography was added and mixed, flow rate: 0.6 mL / min) As a result, it was confirmed that the content of 5-chloro-2-methyl-4-isothiazolin-3-one was 100 ppm.

<Synthesis of silicon materials (silicon-based active materials)>
A mixture of pulverized silicon dioxide powder (average particle size 10 μm) and carbon powder (average particle size 35 μm) was heated in a nitrogen stream (0.5 NL / min) in an electric furnace adjusted to a temperature of 1100 to 1600 ° C. ) A heat treatment for 10 hours was performed to obtain a silicon oxide powder (average particle diameter of 8 μm) represented by the composition formula SiO _x (x = 0.5 to 1.1). 300 g of this silicon oxide powder was charged into a batch-type heating furnace, and the temperature was raised from room temperature (25 ° C.) to 1100 ° C. at a temperature raising rate of 300 ° C./h while maintaining a reduced pressure of 100 Pa absolute pressure with a vacuum pump. . Next, heat treatment (graphite coating treatment) was performed at 1100 ° C. for 5 hours while introducing methane gas at a flow rate of 0.5 NL / min while maintaining the pressure in the heating furnace at 2000 Pa. After the completion of the graphite coating treatment, the powder was cooled to room temperature at a temperature decrease rate of 50 ° C./h to obtain about 330 g of graphite-coated silicon oxide powder. This graphite-coated silicon oxide is a conductive powder (active material) in which the surface of silicon oxide is coated with graphite, and its average particle diameter is 10.5 μm. The ratio of the graphite film in the case of mass% was 2 mass%.

<Preparation of slurry for electricity storage device electrode>
Thickener (trade name “CMC2200”, manufactured by Daicel Corporation) is added to a biaxial planetary mixer (trade name “TK Hibismix 2P-03” manufactured by PRIMIX Co., Ltd.) and 1 part by mass (solid content converted value, concentration). (Added as a 2% by mass aqueous solution), 99 parts by mass (solid content conversion value) of artificial graphite (trade name “MAG”, manufactured by Hitachi Chemical Co., Ltd.) which is highly crystalline graphite as a negative electrode active material, obtained above 1 part by weight (solid content conversion value) of graphitic oxide film coated with silicon oxide, graphene oxide (manufactured by EK Japan Ltd., product name “single-layer graphene oxide”, product number “G17L”) 0.01 part by weight and water 68 parts by mass was added and stirred at 60 rpm for 1 hour. Thereafter, water and the power storage device composition obtained above were added to the obtained paste in an amount corresponding to 2 parts by mass of the polymer (E) contained therein, and the solid content concentration was adjusted to 50% by mass. After that, using a stirring deaerator (trade name “Narutaro Awatori” manufactured by Shinky Co., Ltd.) for 2 minutes at 200 rpm, 5 minutes at 1800 rpm, and further under reduced pressure (about 2.5 × 10 ⁴ Pa) Was stirred and mixed at 1800 rpm for 1.5 minutes to prepare an electricity storage device electrode slurry.

4.1.3. Production and evaluation of electricity storage device electrode <Production of electricity storage device electrode>
The electricity storage device electrode slurry obtained above was uniformly applied to the surface of a current collector made of copper foil having a thickness of 20 μm by a doctor blade method so that the film thickness after drying was 80 μm. Then, it was dried at 120 ° C. for 10 minutes. Then, the electrical storage device electrode (negative electrode) was obtained by pressing with a roll-press machine so that the density of an active material layer may be 1.6 g / cm < ³ >.

<Measurement of peel strength>
A test piece having a width of 2 cm and a length of 12 cm was cut out from the electricity storage device electrode obtained above, and the surface of the test piece on the active material layer side was coated with a double-sided tape having a width of 25 mm (product name “Nystack ( (Registered trademark) ”) and attached to an aluminum plate. On the other hand, a 18 mm wide tape (manufactured by Nichiban Co., Ltd., trade name “Cello Tape (registered trademark)”, prescribed in JIS Z1522) was attached to the surface of the current collector of the test piece. The force (N / m) when this 18 mm wide tape was peeled 2 cm in the 90 ° direction at a speed of 50 mm / min was measured 6 times, and the average value was calculated as the adhesion strength (peel strength, N / m). It can be evaluated that the larger the peel strength value, the higher the adhesion strength between the current collector and the active material layer, and the more difficult the active material layer peels from the current collector. Quantitatively, when the peel strength value is 8 N / m or more, it can be determined that the adhesion strength is good. The measurement results of peel strength are also shown in Table 1.

<Measurement of crack rate>
A test piece having a width of 2 cm and a length of 10 cm was cut out from the power storage device electrode obtained above, and the test piece was repeatedly subjected to a bending test in a width direction of 100 times along a round bar having a diameter of 2 mm. The crack size was measured by visually observing and measuring the size of the crack along the round bar. The crack rate was defined by the following formula (3).
Crack rate (%) = (length with crack [mm] / total length of electrode plate [100 mm]) × 100 (3)

4.1.4. Manufacturing and evaluation of electricity storage devices <Manufacture of counter electrode (positive electrode)>
Biaxial planetary mixer (product name “TK Hibismix 2P-03” manufactured by PRIMIX Corporation) and electrochemical device electrode binder (product name “KF polymer # 1120” manufactured by Kureha Co., Ltd.) 4.0 mass Parts (solid content conversion value), conductive auxiliary agent (manufactured by Denki Kagaku Kogyo Co., Ltd., trade name “Denka Black 50% press product”) 3.0 parts by mass, LiCoO ₂ having an average particle size of 5 μm as a positive electrode active material (Hayashi Kasei) 100 parts by mass (in terms of solid content) and 36 parts by mass of N-methylpyrrolidone (NMP) were added, and the mixture was stirred at 60 rpm for 2 hours. After adding NMP to the obtained paste and adjusting the solid content concentration to 65% by mass, the mixture was stirred at 200 rpm for 2 minutes at 200 rpm using a stirring defoaming machine (trade name “Netaro Awatori”). The positive electrode slurry was prepared by stirring and mixing at 1,800 rpm for 5 minutes and further under reduced pressure (about 2.5 × 10 ⁴ Pa) at 1,800 rpm for 1.5 minutes. The positive electrode slurry was uniformly applied to the surface of the current collector made of aluminum foil by a doctor blade method so that the film thickness after solvent removal was 80 μm, and the solvent was removed by heating at 120 ° C. for 20 minutes. . Then, the counter electrode (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 >.

<Assembly of lithium ion battery cells>
In a glove box substituted with Ar so that the dew point is −80 ° C. or less, the negative electrode produced above was punched and molded to a diameter of 15.95 mm. A bipolar coin cell (trade name “HS Mounted on a 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, 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).

<Evaluation of 10th cycle retention>
About the electrical storage device manufactured above, charging was started at a constant current (0.5 C) in a thermostatic chamber adjusted to 25 ° C., and when the voltage reached 4.2 V, the constant voltage (4. Charging is continued at 2V), and charging is completed (cut off) when the current value reaches 0.05C. Next, discharging was started at a constant current (0.5 C), and when the voltage reached 3 V, discharging was completed (cut off), and the first discharge capacity at 0.5 C was measured. The charge / discharge was repeated 9 times, and the 10th cycle retention rate (%) was calculated by calculating the ratio (percent%) of the 10th discharge capacity to the first discharge capacity.

4.2. Examples 2-9 and Comparative Examples 1-6
The solid content concentration of 35 mass was the same as in Example 1 <Synthesis of (E) polymer particles> except that the type and amount of each monomer were as shown in Tables 1 and 2, respectively. % Aqueous dispersions containing (E) polymer particles were prepared. Next, using the obtained aqueous dispersion, a power storage device composition was prepared in the same manner as in Example 1. Next, using the obtained composition for an electricity storage device, Carbon. By synthesizing graphene oxide with different degrees of oxidation by adjusting the amount of potassium permanganate used as an oxidizing agent when synthesizing graphene oxide by the Hummers method described in 2013, 53, P38-49, Except having changed the content rate of the substance as shown in Table 1-Table 2, the slurry for electrical storage device electrodes was prepared similarly to Example 1, respectively, and the electrical storage device electrode and the electrical storage device were each produced. Various measurement and evaluation methods were the same as those in Example 1.

4.3. Example 10
The inside of an autoclave having an internal volume of about 6 L equipped with an electromagnetic stirrer was sufficiently purged with nitrogen, then 2.5 L of deoxygenated pure water and 25 g of ammonium perfluorodecanoate as an emulsifier were charged and stirred at 350 rpm at 60 ° C. The temperature was raised to. Next, a mixed gas composed of 70% of vinylidene fluoride (VDF) and 30% of propylene hexafluoride (HFP) as monomers was charged until the internal pressure reached 20 kg / cm ² . 25 g of Freon 113 solution containing 20% of diisopropyl peroxydicarbonate as a polymerization initiator was injected using nitrogen gas to initiate polymerization. During the polymerization, a mixed gas composed of 60.2% VDF and 39.8% HFP was sequentially injected so that the internal pressure was maintained at 20 kg / cm ² , and the pressure was maintained at 20 kg / cm ² . Further, since the polymerization rate decreased as the polymerization progressed, the same amount of the same polymerization initiator solution as that described above was injected using nitrogen gas after 3 hours, and the reaction was continued for 3 hours. Thereafter, the reaction liquid was cooled and the stirring was stopped at the same time. After the unreacted monomer was released, the reaction was stopped to obtain an aqueous dispersion containing 40% of polymer fine particles. As a result of analyzing the obtained polymer by ¹⁹ F-NMR, the mass composition ratio of each monomer was VDF / HFP = 21/4.

  After the inside of the 7-liter separable flask was sufficiently purged with nitrogen, 1600 g of an aqueous dispersion containing fine particles of the polymer obtained in the above step (corresponding to 25 parts by mass in terms of polymer), emulsifier “Adekaria Soap SR1025 "(trade name, manufactured by ADEKA Corporation) 0.5 parts by mass, methyl methacrylate (MMA) 30 parts by mass, 2-ethylhexyl acrylate (EHA) 40 parts by mass, methacrylic acid (MAA) 5 parts by mass, and water 130 parts by mass were sequentially added and stirred at 70 ° C. for 3 hours to allow the polymer fine particles to absorb the monomer. Next, 20 mL of a tetrahydrofuran solution containing 0.5 part by mass of azobisisobutyronitrile, which is an oil-soluble polymerization initiator, is added, heated to 75 ° C., reacted for 3 hours, and further reacted at 85 ° C. for 2 hours. went. Then, after cooling, the reaction was stopped, and the aqueous dispersion containing 40% of the polymer particles (E) was obtained by adjusting the pH to 7 with a 2.5N aqueous sodium hydroxide solution.

Subsequently, the composition for electrical storage devices was prepared like Example 1 using the obtained aqueous dispersion. Next, using the obtained power storage device composition, slurry for power storage device electrodes was prepared in the same manner as in Example 1 except that the content ratio of graphene oxide and active material was as shown in Table 1. A device electrode and an electricity storage device were produced. Various measurement and evaluation methods were the same as those in Example 1.

4.4. Comparative Example 7
A slurry for an electricity storage device electrode was prepared in the same manner as in Example 10 except that no silicon-based material was added as an active material, and an electricity storage device electrode and an electricity storage device were produced. Various measurements and evaluation methods were the same as those in Example 1.

4.5. Evaluation results Tables 1 and 2 below summarize the (A) polymer composition used in Examples 1 to 10 and Comparative Examples 1 to 7, the composition of the slurry for the electricity storage device electrode, and various evaluation results.

Abbreviations of monomers in Tables 1 and 2 have the following meanings, respectively.
-BD: 1,3-butadiene-ST: styrene-MMA: methyl methacrylate-AN: acrylonitrile-HEMA: 2-hydroxyethyl methacrylate-2EHA: 2-hydroxyethyl acrylate-AA: acrylic acid-MAA: methacrylic acid -TA: Itaconic acid-VDF: Vinylidene fluoride-HFP: Propylene hexafluoride

The abbreviations of the active materials in Table 1 have the following meanings, respectively.
-Silicon-based active material: Graphite-coated silicon oxide synthesized above-Carbon-based active material: manufactured by Hitachi Chemical Co., Ltd., trade name "MAG"
Graphene: manufactured by Graphene Platform Co., Ltd., product name “graphene dispersion”, product model number “GNH-XX / W”
-Acetylene black: manufactured by Denki Kagaku Kogyo Co., Ltd., trade name “Denka Black 50% Pressed Product”

  As apparent from Table 1 above, the slurry for the electricity storage device electrode prepared using the composition for electricity storage device according to the present invention shown in Examples 1 to 13 was compared with the cases of Comparative Examples 1 to 6. Thus, an electricity storage device electrode having good adhesion and excellent crack resistance was provided. Moreover, it turned out that cycling characteristics become favorable for an electrical storage device (lithium ion secondary battery) provided with these electrical storage device electrodes.

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

DESCRIPTION OF SYMBOLS 10 ... Current collector, 20 ... Active material layer, 100 ... Electric storage device electrode

Claims (9)

Containing (A) silicon material and (B) carbon material as active materials,
Furthermore, the slurry for electrical storage device electrodes containing (C) graphene derivative and (D) liquid medium.   The slurry for an electricity storage device electrode according to claim 1, comprising 0.001 to 20 parts by mass of the (C) graphene derivative with respect to a total of 100 parts by mass of the (A) silicon material and the (B) carbon material. .   The amount of the (A) silicon material is 1 to 50% by mass when the total amount of the (A) silicon material and the (B) carbon material is 100% by mass. A slurry for an electricity storage device electrode.   The slurry for an electricity storage device electrode according to any one of claims 1 to 3, wherein the (C) graphene derivative is graphene oxide.   (E) The slurry for electrical storage device electrodes as described in any one of Claims 1 thru | or 4 which further contains a polymer.   The polymer (E) is a repeating unit derived from a conjugated diene compound, a repeating unit derived from an aromatic vinyl compound, a repeating unit derived from an unsaturated carboxylic acid ester, and a repeating unit derived from an unsaturated carboxylic acid. The slurry for an electricity storage device electrode according to claim 5, wherein the slurry is a diene polymer.   The said (E) polymer is a fluorine-containing polymer containing the repeating unit derived from a fluorine-containing ethylene-type monomer, and the repeating unit derived from unsaturated carboxylic acid ester of Claim 5. A slurry for an electricity storage device electrode.   An electricity storage device electrode comprising: a current collector; and a layer formed by applying and drying the electricity storage device electrode slurry according to any one of claims 1 to 7 on a surface of the current collector. .   An electricity storage device comprising the electricity storage device electrode according to claim 8.

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