Binder composition for capacitor devices, slurry for capacitor device electrodes, capacitor device electrodes, and capacitor devices

Abstract

The present invention provides a binder composition for a capacitor device capable of manufacturing a capacitor device electrode that has excellent repetitive charge / discharge characteristics by reducing internal resistance and excellent charge / discharge durability characteristics under high temperatures by improving adhesion. A binder composition for a capacitor device according to the present invention comprises a polymer (A) and a liquid medium (B), wherein when the total number of repeating units included in the polymer (A) is 100 mass%, the polymer (A) comprises 15 to 60 mass% of repeating units (a1) derived from a conjugated diene compound and 1 to 10 mass% of repeating units (a2) derived from an unsaturated carboxylic acid, and the peak tops of the dynamic viscoelasticity tanδ (loss modulus / storage modulus) of the polymer (A) are one in the range of -40°C or higher and less than 50°C, and one in the range of 50°C or higher and less than 150°C, and when the tanδ of the peak top in the range of -40°C or higher and less than 50°C is denoted as tanδ(Tp1) and the tanδ of the peak top in the range of 50°C or higher and less than 150°C is denoted as tanδ(Tp2), the relationship of the following formula (1) is satisfied. tanδ(Tp2) / tanδ(Tp1)≥0.5 (1)

Description

Technology Field

[0001] The present invention relates to a binder composition for a capacitor device, a slurry for a capacitor device electrode containing the binder composition and an active material, a capacitor device electrode formed by applying and drying the slurry on a current collector, and a capacitor device having the capacitor device electrode. Background Technology

[0002] In recent years, there has been a demand for energy storage devices that possess high voltage and high energy density as power sources for driving electronic devices. Lithium-ion batteries and lithium-ion capacitors are expected to serve as such storage devices.

[0003] The electrode used in such a capacitor device is manufactured by applying and drying a composition (slurry for capacitor device electrodes) containing an active material and a polymer that functions as a binder onto the surface of a current collector. The characteristics required of the polymer used as a binder include the ability to bond between active materials and the ability to adhere between the active material and the current collector, resistance to abrasion during the electrode winding process, and resistance to powder drop so that fine particles of the active material do not fall off from the coated and dried composition film (hereinafter also referred to as the "active material layer") even during subsequent cutting. By allowing such a binder material to exhibit good adhesion and reducing the internal resistance of the battery caused by the binder material, good charge and discharge characteristics can be imparted to the capacitor device.

[0004] Furthermore, it has been empirically established that the bonding ability between the active materials, the adhesion ability between the active material and the current collector, and the resistance to powder drop are in a nearly proportional relationship. Therefore, in this specification, the term "adhesion" may be used to encompass these aspects below.

[0005] In addition, in recent years, research and development of electric vehicles equipped with energy storage devices has been actively conducted with the aim of reducing environmental burden. When energy storage devices are installed as driving power sources for electric vehicles, high input / output characteristics capable of frequently repeating charging and discharging are required, and for this, it is important to lower the resistance. Furthermore, since the temperature inside the vehicle can reach high temperatures of 50°C or higher during the summer, durability under high temperatures is required for the energy storage devices.

[0006] Against this backdrop, various binder materials have been proposed to lower the resistance and improve the charge / discharge durability characteristics of capacitor devices (see, for example, Patent Documents 1 and 2). Prior art literature

[0007] International Publication No. 2015 / 012366 and Japanese Patent Publication No. 2017-126456 The problem to be solved

[0008] However, the binder materials disclosed in the above patent documents 1 and 2 do not have sufficient repeated charge / discharge characteristics or durability under high temperatures, and further improvement was required in order to apply them to energy storage devices as driving power sources for electric vehicles.

[0009] Accordingly, several embodiments according to the present invention provide a binder composition for a capacitor device capable of manufacturing a capacitor device electrode that has excellent repetitive charge / discharge characteristics by reducing internal resistance and excellent charge / discharge durability characteristics at high temperatures by improving adhesion. Additionally, several embodiments according to the present invention provide a slurry for a capacitor device electrode containing the said binder composition. Furthermore, several embodiments according to the present invention provide a capacitor device electrode that has excellent repetitive charge / discharge characteristics by reducing internal resistance and excellent charge / discharge durability characteristics at high temperatures by improving adhesion. Additionally, several embodiments according to the present invention provide a capacitor device that has excellent repetitive charge / discharge characteristics and excellent charge / discharge durability characteristics at high temperatures. means of solving the problem

[0010] The present invention is made to solve at least part of the above-described problem and can be realized in any of the following embodiments.

[0011] One embodiment of a binder composition for a capacitor device according to the present invention is,

[0012] It contains a polymer (A) and a liquid medium (B),

[0013] When the total sum of the repeating units included in the polymer (A) is set to 100 mass%, the polymer (A)

[0014] 15 to 60 mass% of repeating units (a1) derived from a conjugated diene compound, and

[0015] 1 to 10 mass% of repeating units (a2) derived from an unsaturated carboxylic acid

[0016] Contains,

[0017] The peak top of tanδ (loss modulus / storage modulus) of the dynamic viscoelasticity of the polymer (A) is one in the range of -40°C or higher and less than 50°C, and also one in the range of 50°C or higher and less than 150°C.

[0018] When tanδ of the peak top in the range of -40℃ or higher and less than 50℃ is denoted as tanδ(Tp1) and tanδ of the peak top in the range of 50℃ or higher and less than 150℃ is denoted as tanδ(Tp2), the relationship of the following equation (1) is satisfied.

[0019] tanδ(Tp2) / tanδ(Tp1)≥0.5 (1)

[0020] In one embodiment of the above-described binder composition for a capacitor device,

[0021] The above polymer (A) may further contain 35 to 75 mass% of repeating units (a3) ​​derived from aromatic vinyl compounds, and

[0022] In this case, the total amount of the repeating unit (a1), the repeating unit (a2), and the repeating unit (a3) ​​may be 80 mass% or more.

[0023] In one embodiment of the above-described binder composition for a capacitor device,

[0024] The polymer (A) may contain at least one of a repeating unit (a4) derived from an unsaturated carboxylic acid ester and a repeating unit (a5) derived from an α,β-unsaturated nitrile compound, and

[0025] In this case, the total amount of the repeating unit (a1), the repeating unit (a2), the repeating unit (a4) and the repeating unit (a5) may be 65 mass% or more.

[0026] In any embodiment of the above-mentioned binder composition for a capacitor device,

[0027] The martens hardness calculated using the picoindenter of the above polymer (A) may be 15 MPa or higher.

[0028] In any embodiment of the above-mentioned binder composition for a capacitor device,

[0029] The above polymer (A) is a polymer particle, and

[0030] The number average particle size of the above polymer particles may be 50 nm or more and 500 nm or less.

[0031] In any embodiment of the above-mentioned binder composition for a capacitor device,

[0032] The above liquid medium (B) may be water.

[0033] One embodiment of the slurry for an electrode of a capacitor device according to the present invention is,

[0034] A binder composition for a capacitor device of any of the above embodiments and an active material are included.

[0035] In one embodiment of the above-mentioned slurry for capacitor device electrodes,

[0036] The above active material may contain silicon material.

[0037] One embodiment of the capacitor device electrode according to the present invention is,

[0038] It comprises a current collector and an active material layer formed by applying and drying a slurry for an electrode of any of the above embodiments of the capacitor on the surface of the current collector.

[0039] One embodiment of the capacitor device according to the present invention is,

[0040] The above-described embodiment is provided with a capacitor device electrode. Effects of the invention

[0041] According to the binder composition for a capacitor device according to the present invention, since internal resistance can be reduced, the repetitive charge-discharge characteristics are excellent, and since adhesion can be improved, a capacitor device electrode with excellent charge-discharge durability characteristics under high temperatures can be manufactured. The binder composition for a capacitor device according to the present invention exhibits the above effects particularly when the capacitor device electrode contains a material with a large lithium absorption capacity as an active material, such as a carbon material like graphite or a silicon material. As such, since a material with a large lithium absorption capacity can be used as the active material of the capacitor device electrode, battery performance is also improved. Brief explanation of the drawing

[0042] Figure 1 is a diagram illustrating the relationship between the measurement temperature and tanδ in the measurement of dynamic viscoelasticity of the film produced in Example 3. Specific details for implementing the invention

[0043] Suitable embodiments according to the present invention will be described in detail below. Furthermore, the present invention is not limited to the embodiments described below, and should be understood to include various modifications implemented within the scope that does not alter the essence of the invention.

[0044] Furthermore, in this specification, the term “(meth)acrylic acid~” is a concept encompassing both “acrylic acid~” and “methacrylic acid~”. Likewise, the term “~(meth)acrylate” is a concept encompassing both “~acrylate” and “~methacrylate”. Likewise, the term “(meth)acrylamide” is a concept encompassing both “acrylamide” and “methacrylamide”.

[0045] In this specification, numerical ranges described as “A to B” are interpreted as including numerical value A as a lower limit and numerical value B as an upper limit.

[0046] In this specification, "high temperature" refers to an environment with a temperature range of approximately 40°C to 80°C.

[0047] 1. Binder composition for capacitor devices

[0048] A binder composition for a capacitor device according to one embodiment of the present invention comprises a polymer (A) and a liquid medium (B). When the total number of repeating units included in the polymer (A) is 100 mass%, the polymer (A) contains 15 to 60 mass% of repeating units (a1) derived from a conjugated diene compound and 1 to 10 mass% of repeating units (a2) derived from an unsaturated carboxylic acid. In addition, when the peak tops of the dynamic viscoelasticity tanδ (loss modulus / storage modulus) of the polymer (A) are in the range of -40°C or higher and less than 50°C, and in the range of 50°C or higher and less than 150°C, and the tanδ of the peak top in the range of -40°C or higher and less than 50°C is denoted as tanδ(Tp1), and the tanδ of the peak top in the range of 50°C or higher and less than 150°C is denoted as tanδ(Tp2), the relationship of the following equation (1) is satisfied.

[0049] tanδ(Tp2) / tanδ(Tp1)≥0.5 (1)

[0050] The binder composition for a capacitor device according to the present embodiment may be used as a material for manufacturing a capacitor device electrode (active material layer) that improves the bonding ability between active materials, the adhesion ability between the active material and the current collector, and resistance to powder drop, and may also be used as a material for forming a protective film to suppress short circuits caused by dendrites occurring during charging and discharging. Hereinafter, each component included in the binder composition for a capacitor device according to the present embodiment will be described in detail.

[0051] 1.1. Polymer (A)

[0052] A binder composition for a capacitor device according to the present embodiment contains a polymer (A). When the total number of repeating units included in the polymer (A) is 100 mass%, the polymer (A) contains 15 to 60 mass% of a repeating unit (a1) derived from a conjugated diene compound (hereinafter also simply referred to as "repeating unit (a1)") and 1 to 10 mass% of a repeating unit (a2) derived from an unsaturated carboxylic acid (hereinafter also simply referred to as "repeating unit (a2)"). In addition, the polymer (A) may contain, in addition to the above repeating units, repeating units derived from other monomers copolymerizable with them.

[0053] The polymer (A) included in the binder composition for a capacitor device according to the present embodiment may be in a latex form dispersed in a liquid medium (B) or dissolved in a liquid medium (B), but it is preferable that it be in a latex form dispersed in a liquid medium (B). It is preferable that the polymer (A) be in a latex form dispersed in a liquid medium (B) because the stability of the capacitor device electrode slurry (hereinafter also simply referred to as "slurry") produced by mixing with an active material is improved, and the coating properties of the slurry onto the current collector are also improved.

[0054] Hereinafter, the repeating unit constituting the polymer (A), the physical properties of the polymer (A), and the manufacturing method will be explained in that order.

[0055] 1.1.1. Repeating unit constituting polymer (A)

[0056] 1.1.1.1. Repeating unit derived from a conjugated diene compound (a1)

[0057] The content ratio of repeating units (a1) derived from conjugated diene compounds is 15 to 60 mass% when the total number of repeating units included in the polymer (A) is 100 mass%. The lower limit of the content ratio of repeating units (a1) is preferably 17 mass%, and more preferably 20 mass%. The upper limit of the content ratio of repeating units (a1) is preferably 57 mass%, and more preferably 55 mass%. By having the polymer (A) contain repeating units (a1) within the above range, the dispersibility of the active material or filler is improved, making it possible to produce a uniform active material layer or protective film, thereby eliminating structural defects in the electrode plate and exhibiting good repetitive charge / discharge characteristics. In addition, elasticity can be imparted to the polymer (A) covering the surface of the active material, and adhesion can be improved as the polymer (A) stretches, thereby exhibiting good charge / discharge durability characteristics.

[0058] As conjugated diene compounds, examples include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chlor-1,3-butadiene, etc., although not particularly limited, and one or more selected from these may be used. Among these, 1,3-butadiene is particularly preferred.

[0059] 1.1.1.2. Repeating unit derived from an unsaturated carboxylic acid (a2)

[0060] The content ratio of repeating units (a2) derived from unsaturated carboxylic acid is 1 to 10 mass% when the total number of repeating units included in the polymer (A) is 100 mass%. The lower limit of the content ratio of repeating units (a2) is preferably 1.2 mass%, and more preferably 1.5 mass%. The upper limit of the content ratio of repeating units (a2) is preferably 9 mass%, and more preferably 8 mass%. By having the polymer (A) contain repeating units (a2) within the above range, the dispersibility of the active material or filler is improved. In addition, by improving the affinity with the silicon material used as the active material and suppressing the swelling of the silicon material, good charge / discharge durability characteristics are exhibited.

[0061] As unsaturated carboxylic acids, examples include monocarboxylic acids and dicarboxylic acids (including anhydrides), such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid, although they are not particularly limited. One or more selected from these may be used. As unsaturated carboxylic acids, it is preferable to use one or more selected from acrylic acid, methacrylic acid, and itaconic acid.

[0062] 1.1.1.3. Other repeating units

[0063] The polymer (A) may contain repeating units derived from other monomers copolymerizable with the above repeating units (a1) to (a2). Examples of such repeating units include a repeating unit (a3) ​​derived from an aromatic vinyl compound (hereinafter simply referred to as "repeating unit (a3)"), a repeating unit (a4) derived from an unsaturated carboxylic acid ester (hereinafter simply referred to as "repeating unit (a4)"), a repeating unit (a5) derived from an α,β-unsaturated nitrile compound (hereinafter simply referred to as "repeating unit (a5)"), a repeating unit (a6) derived from (meth)acrylamide (hereinafter simply referred to as "repeating unit (a6)"), a repeating unit (a7) derived from a compound having a sulfonic acid group (hereinafter simply referred to as "repeating unit (a7)"), a repeating unit derived from a cationic monomer, etc.

[0064] <Repeating unit derived from aromatic vinyl compounds (a3)>

[0065] The content ratio of repeating units (a3) ​​derived from aromatic vinyl compounds is preferably 35 to 75 mass% when the total number of repeating units included in the polymer (A) is 100 mass%. The lower limit of the content ratio of repeating units (a3) ​​is preferably 38 mass%, and more preferably 40 mass%. The upper limit of the content ratio of repeating units (a3) ​​is preferably 72 mass%, and more preferably 70 mass%. By containing repeating units (a3) ​​within the above range, the polymer (A) suppresses the fusion of polymers (A) dispersed within the electrode, thereby improving the permeability of the electrolyte and exhibiting good repetitive charge / discharge characteristics. Additionally, it may exhibit good binding strength to graphite or the like used as an active material, thereby obtaining an electrostatic device electrode with excellent adhesion.

[0066] Aromatic vinyl compounds are not particularly limited, but examples include styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, chlorostyrene, divinylbenzene, etc., and one or more selected from these may be used.

[0067] When the polymer (A) contains repeating units (a3) ​​derived from aromatic vinyl compounds, when the total amount of repeating units included in the polymer (A) is 100 mass%, the total amount of repeating units (a1), repeating units (a2), and repeating units (a3) ​​is preferably 80 mass% or more, and more preferably 85 mass% or more. If the total amount of repeating units (a1), repeating units (a2), and repeating units (a3) ​​is within the above range, the dispersibility of the active material or filler is improved, and the fusion of polymers (A) dispersed in the electrode can be suppressed, thereby improving adhesion and the penetration of the electrolyte, so good repeated charge / discharge characteristics and good charge / discharge durability characteristics are exhibited.

[0068] <Repeating unit derived from unsaturated carboxylic acid ester (a4)>

[0069] The polymer (A) may contain repeating units (a4) derived from unsaturated carboxylic acid esters. The content ratio of the repeating units (a4) is preferably 0 to 60 mass% when the total number of repeating units included in the polymer (A) is 100 mass%. The lower limit of the content ratio of the repeating units (a4) is preferably 1 mass%, and more preferably 2 mass%. The upper limit of the content ratio of the repeating units (a4) is preferably 55 mass%, and more preferably 50 mass%. By having the polymer (A) contain repeating units (a4) within the above range, the affinity between the polymer (A) and the electrolyte is improved, and the increase in internal resistance caused by the binder becoming an electrical resistance component in the capacitor device is suppressed, and the decrease in adhesion caused by excessive absorption of the electrolyte can be prevented.

[0070] Among unsaturated carboxylic acid esters, (meth)acrylic acid esters can be preferably used. Specific examples of (meth)acrylic acid esters include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-amyl (meth)acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, and hexa(meth)acrylate. Examples include dipentaerythritol, allyl (meth)acrylate, 2-hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, glycerin mono(meth)acrylate, glycerin di(meth)acrylate, etc., and one or more selected from these may be used. Among these, it is preferable that it be one or more selected from (meth)acrylate methyl, (meth)acrylate ethyl, (meth)acrylate n-butyl, (meth)acrylate 2-ethylhexyl, (meth)acrylate cyclohexyl, di(meth)acrylate ethylene glycol, and (meth)acrylate 2-hydroxyethyl, and it is particularly preferable that it be (meth)acrylate methyl.

[0071] <Repeating unit (a5) derived from an α,β-unsaturated nitrile compound>

[0072] The polymer (A) may contain repeating units (a5) derived from an α,β-unsaturated nitrile compound. The content ratio of the repeating units (a5) is preferably 0 to 60 mass% when the total number of repeating units included in the polymer (A) is 100 mass%. The lower limit of the content ratio of the repeating units (a5) is preferably 0.5 mass%, and more preferably 1 mass%. The upper limit of the content ratio of the repeating units (a5) is preferably 55 mass%, and more preferably 50 mass%. By having the polymer (A) contain repeating units (a5) within the above range, it is possible to reduce the dissolution of the polymer (A) into the electrolyte, thereby suppressing the decrease in adhesion caused by the electrolyte. Additionally, it may be possible to suppress the increase in internal resistance caused by the dissolved polymer component becoming an electrical resistance component in the capacitor device.

[0073] As for α,β-unsaturated nitrile compounds, examples include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile, vinylidene cyanide, etc., although not particularly limited, and one or more selected from these may be used. Among these, one or more selected from the group consisting of acrylonitrile and methacrylonitrile are preferred, and acrylonitrile is particularly preferred.

[0074] When the polymer (A) contains at least one of a repeating unit (a4) derived from an unsaturated carboxylic acid ester and a repeating unit (a5) derived from an α,β-unsaturated nitrile compound, when the total amount of repeating units included in the polymer (A) is 100 mass%, the total amount of repeating unit (a1), repeating unit (a2), repeating unit (a4), and repeating unit (a5) is preferably 65 mass% or more, and more preferably 68 mass% or more. If the total amount of repeating unit (a1), repeating unit (a2), repeating unit (a4), and repeating unit (a5) is within the above range, the dispersibility of the active material or filler is improved, and the fusion of polymers (A) dispersed in the electrode can be suppressed, thereby improving adhesion and the penetration of the electrolyte, so good repeated charge / discharge characteristics and good charge / discharge durability characteristics are exhibited.

[0075] <Repeating unit derived from (meth)acrylamide (a6)>

[0076] The polymer (A) may contain repeating units (a6) derived from (meth)acrylamide. The content ratio of the repeating units (a6) is preferably 0 to 10 mass% when the total number of repeating units included in the polymer (A) is 100 mass%. The lower limit of the content ratio of the repeating units (a6) is preferably 1 mass%, and more preferably 2 mass%. The upper limit of the content ratio of the repeating units (a6) is preferably 8 mass%, and more preferably 5 mass%. By including repeating units (a6) in the polymer (A) within the above range, the dispersibility of the active material or filler in the slurry may be improved. In addition, the flexibility of the obtained active material layer may be appropriate, and the adhesion between the current collector and the active material layer may be improved. Furthermore, since the bonding ability between active materials containing carbon materials such as graphite or silicon materials can be increased, an active material layer with better flexibility and adhesion to the current collector may be obtained.

[0077] Examples of (meth)acrylamides are not particularly limited but include acrylamide, methacrylamide, N-isopropylacrylamide, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N,N-diethylacrylamide, N,N-diethylmethacrylamide, N,N-dimethylaminopropylacrylamide, N,N-dimethylaminopropylmethacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, diacetoneacrylamide, maleamide, acrylamide tert-butylsulfonic acid, etc., and one or more selected from these may be used.

[0078] <Repeating unit (a7) derived from a compound having a sulfonic acid group>

[0079] The polymer (A) may contain repeating units (a7) derived from a compound having a sulfonic acid group. The content ratio of the repeating units (a7) is preferably 0 to 10 mass% when the total number of repeating units included in the polymer (A) is 100 mass%. The lower limit of the content ratio of the repeating units (a7) is preferably 0.5 mass%, and more preferably 1 mass%. The upper limit of the content ratio of the repeating units (a7) is preferably 8 mass%, and more preferably 5 mass%.

[0080] Compounds having a sulfonic acid group are not particularly limited, but include compounds such as vinylsulfonic acid, styrenesulfonic acid, allylsulfonic acid, sulfoethyl (meth)acrylate, sulfopropyl (meth)acrylate, sulfobutyl (meth)acrylate, 2-acrylamide-2-methylpropanesulfonic acid, 2-hydroxy-3-acrylamidopropanesulfonic acid, 3-allyloxy-2-hydroxypropanesulfonic acid, and alkali salts thereof, and one or more selected from these may be used.

[0081] <Repeating unit derived from cationic monomers>

[0082] The polymer (A) may contain repeating units derived from cationic monomers. As for the cationic monomer, it is not particularly limited, but it is preferred to be at least one monomer selected from the group consisting of secondary amines (salts), tertiary amines (salts), and quaternary ammonium salts. Specific examples of these cationic monomers are not particularly limited, but include (meth)acrylic acid 2-(dimethylamino)ethyl, dimethylaminoethyl (meth)acrylate methyl quaternary chloride, (meth)acrylic acid 2-(diethylamino)ethyl, (meth)acrylic acid 3-(dimethylamino)propyl, (meth)acrylic acid 3-(diethylamino)propyl, (meth)acrylic acid 4-(dimethylamino)phenyl, (meth)acrylic acid 2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl, (meth)acrylic acid 2-(0-[1'-methylpropylideneamino]carboxyamino)ethyl, (meth)acrylic acid 2-(1-aziridinyl)ethyl, methacloylcholine chloride, isocyanuric acid tris(2-acryloyloxyethyl), 2-vinylpyridine, quinaldine red, Examples include 1,2-di(2-pyridyl)ethylene, 4'-hydrazino-2-stilbazole dihydrochloride hydrate, 4-(4-dimethylaminostyryl)quinoline, 1-vinylimidazole, diallylamine, diallylamine hydrochloride, trialylamine, diallyldimethylammonium chloride, dichlormid, N-allylbenzylamine, N-allylaniline, 2,4-diamino-6-diallylamino-1,3,5-triazine, N-trans-cinnamyl-N-methyl-(1-naphthylmethyl)amine hydrochloride, trans-N-(6,6-dimethyl-2-hepten-4-inyl)-N-methyl-1-naphthylmethylamine hydrochloride, etc., and one or more selected from these may be used.

[0083] 1.1.2. Physical properties of polymer (A)

[0084] 1.1.2.1. Dynamic Viscoelasticity

[0085] When the dynamic viscoelasticity of the polymer (A) is measured, there is one peak top of tanδ (loss modulus / storage modulus) in the range of -40°C to less than 50°C and one peak top in the range of 50°C to less than 150°C. Then, when tanδ of the peak top in the range of -40°C to less than 50°C is denoted as tanδ(Tp1) and tanδ of the peak top in the range of 50°C to less than 150°C is denoted as tanδ(Tp2), the relationship of Equation (1) below is satisfied.

[0086] tanδ(Tp2) / tanδ(Tp1)≥0.5 (1)

[0087] The measurement sample for this dynamic viscoelasticity measurement is a film of polymer (A). The film of polymer (A) is produced by drying polymer (A) at 40°C for 24 hours to produce a uniform film with a thickness of 1.0 ± 0.3 mm, drying this film in a vacuum dryer at 160°C for 30 minutes, and then cutting it into a 10 mm × 10 mm rectangle. Subsequently, using the dynamic viscoelasticity measurement device described below, the measurement sample is fixed to a parallel plate (product name “PP-12”), and the measurement is performed in a temperature range of -70°C to 180°C under the following measurement conditions.

[0088] · Measurement conditions: Shear mode, measurement frequency 0.01 to 1 Hz, heating rate 0.1 ℃ / min

[0089] · Dynamic Viscoelasticity Measuring Device: Manufactured by Anton Paar, Model "MCR 301"

[0090] The value of "tanδ(Tp2) / tanδ(Tp1)" of the polymer (A) used in the present embodiment is 0.5 or higher, preferably 0.75 or higher, and more preferably 1 or higher. If the value of "tanδ(Tp2) / tanδ(Tp1)" of the polymer (A) is within the above range, it indicates that the viscosity is high at a temperature near the peak top temperature of tanδ(Tp1), and it is believed that adhesion can be ensured by this high viscosity. In addition, it indicates high crosslinking at a temperature near the peak top temperature of tanδ(Tp2), that is, that the polymer (A) is rigid, and since the polymer (A) is rigid, it is believed that the particle shape can be maintained without being crushed like other binders during electrode fabrication, thereby increasing the penetration of the electrolyte into the active material. As such, the polymer (A) used in this embodiment can reduce internal resistance by increasing the penetration of the electrolyte into the active material, thereby enabling the fabrication of an electrode exhibiting good repeated charge-discharge characteristics. In addition, the polymer (A) used in this embodiment can improve adhesion, thereby enabling the fabrication of an electrode exhibiting good charge-discharge durability characteristics under high temperatures.

[0091] In the measurement of dynamic viscoelasticity of the polymer (A), the temperature Tp1 (°C) of the peak top of tanδ is preferably in a temperature range of -35°C or higher and 45°C or lower, more preferably -30°C or higher and 40°C or lower. Additionally, it is preferable that there be only one peak top within the above temperature range. The presence of only one Tp within the above temperature range indicates that the viscosity is high within that temperature range. It is believed that, depending on this high viscosity, the polymer (A) can maintain high binding strength within that temperature range, thereby enabling good adhesion.

[0092] In the dynamic viscoelasticity measurement of the polymer (A), the temperature Tp2 (°C) of the peak top of tanδ is preferably in a temperature range of 60°C or higher and 145°C or lower, more preferably 70°C or higher and 140°C or lower. Additionally, it is preferable that there be only one peak top within the above temperature range. The presence of only one Tp within the above temperature range indicates that a polymer with a uniform cross-linking composition is formed within the same temperature range. It is believed that by having a large amount of the uniform cross-linking composition of the polymer (A) within the same temperature range, the hardness of the polymer (A) can be expressed and internal resistance can be reduced.

[0093] As a method for adjusting the temperature Tp of the peak top of tanδ, methods such as adjusting the monomer composition during polymerization of the polymer (A) can be used.

[0094] The tanδ (Tp1) of the polymer (A) is preferably 0.01 to 0.5, more preferably 0.01 to 0.45, and particularly preferably 0.01 to 0.4. The fact that the tanδ (Tp1) of the polymer (A) is within the above range indicates that the polymer (A) has viscosity but is not too hard, and has sufficient binding force to maintain the electrode structure.

[0095] The tanδ (Tp2) of the polymer (A) is preferably 0.1 to 3, more preferably 0.2 to 2.5, and particularly preferably 0.3 to 2. The fact that the tanδ (Tp2) of the polymer (A) is within the above range indicates that the polymer (A) is not too flexible and has sufficient hardness to suppress fusion between particles.

[0096] Methods for adjusting tanδ(Tp) include changing the glass transition temperature or gel content of the polymer (A), or changing the method of adding monomer during polymerization of the polymer (A).

[0097] 1.1.2.2. Martens Hardness

[0098] The martens hardness of the polymer (A) used in the present embodiment, calculated using a picoindenter, is preferably 15 MPa or higher, more preferably 20 MPa or higher, and particularly preferably 25 MPa or higher. The fact that the martens hardness of the polymer (A) is within the above range indicates that the polymer (A) is hard. Since the polymer (A) is hard, it is believed that the penetration of the electrolyte into the active material can be increased because it can maintain its particle shape without being crushed like other binders during electrode fabrication. Since this polymer (A) can reduce internal resistance by increasing the penetration of the electrolyte into the active material, it is possible to fabricate an electrode exhibiting good repeated charge-discharge characteristics.

[0099] The martens hardness of polymer (A) can be measured using a picoindenter. The measurement sample for this picoindenter is a thin film of polymer (A). The thin film of polymer (A) is formed by adding about 1 g of polymer (A) onto a 1 cm × 1 cm Si wafer, forming a film using spin coating with the apparatus and conditions described below, and drying the film on a hot plate at 150°C for 30 minutes. For this measurement sample, the martens hardness is calculated using the picoindenter described below under the following test conditions.

[0100] · Spin coating rotation conditions: Coating was performed according to 150 rpm × 5 seconds, 250 rpm × 5 seconds, and 1000 rpm × 30 seconds.

[0101] · Spin Coating Device: Mikasa Kabushiki Kaisha, Model "MS-A-150"

[0102] · Picoindenter test conditions: Pressed in with a pressure of 0.1 mN for 5 seconds, held for 1 second, and then released over 5 seconds.

[0103] · Picoindent device: Manufactured by Helmut Fischer, Model "HM500"

[0104] 1.1.2.3. Number Average Particle Size

[0105] When the polymer (A) is a particle, the number average particle size of the particle is preferably 50 nm or more and 500 nm or less, more preferably 60 nm or more and 450 nm or less, and particularly preferably 70 nm or more and 400 nm or less. When the number average particle size of the polymer (A) particle is within the above range, the polymer (A) particle is easily adsorbed onto the surface of the active material, so the polymer (A) particle can follow and move along with the movement of the active material. As a result, migration can be suppressed, so the deterioration of electrical properties can be reduced.

[0106] In addition, the number average particle size of the polymer (A) particles can be calculated from the average value of particle sizes obtained from images of 50 particles observed by a transmission electron microscope (TEM). Examples of transmission electron microscopes include the “H-7650” manufactured by Hitachi High Technologies Co., Ltd.

[0107] 1.1.2.4. Electrolyte Swelling Degree

[0108] The degree of electrolyte swelling of the polymer (A) is preferably 100 to 500 mass%, more preferably 120 to 450 mass%, and particularly preferably 140 to 400 mass%. When the degree of electrolyte swelling is within the above range, the polymer (A) can be suitably swollen with respect to the electrolyte. As a result, solvated lithium ions can easily reach the active material, and the internal resistance of the electrode can be reduced, thereby realizing better repeated charge-discharge characteristics. In addition, if the degree of electrolyte swelling is within the above range, the adhesion is also excellent because no large volume change occurs. The degree of electrolyte swelling of the polymer (A) can be measured by the method described in the examples described below.

[0109] 1.1.3. Method for manufacturing polymer (A)

[0110] The method for manufacturing the polymer (A) is not particularly limited, but, for example, can be carried out by an emulsion polymerization method in the presence of known emulsifiers (surfactants), chain transfer agents, polymerization initiators, etc. As emulsifiers (surfactants), chain transfer agents, and polymerization initiators, compounds described in Japanese Patent Publication No. 5999399, etc. may be used.

[0111] The emulsion polymerization method for synthesizing polymer (A) may be carried out as a single-stage polymerization or as a multi-stage polymerization of two or more stages.

[0112] When the synthesis of polymer (A) is carried out by single-stage polymerization, the mixture of monomers may be subjected to emulsion polymerization in the presence of a suitable emulsifier, chain transfer agent, polymerization initiator, etc., preferably at 40 to 80°C, preferably for 4 to 36 hours.

[0113] When synthesizing polymer (A) by two-stage polymerization, it is preferable to set the polymerization of each stage as follows.

[0114] The usage ratio of the monomer used in the first stage polymerization is preferably in the range of 20 to 100 mass% with respect to the total mass of the monomer (the sum of the mass of the monomer used in the first stage polymerization and the mass of the monomer used in the second stage polymerization), and more preferably in the range of 25 to 100 mass%. By performing the first stage polymerization with such a monomer usage ratio, it is desirable to obtain particles of polymer (A) with excellent dispersion stability and a low likelihood of aggregate formation, while also suppressing the increase in viscosity over time of the binder composition for the capacitor device.

[0115] The type of monomer used in the second polymerization and its usage ratio may be the same as or different from the type of monomer used in the first polymerization.

[0116] The polymerization conditions for each step are preferably as follows, in terms of the dispersibility of the obtained polymer (A) particles.

[0117] · First stage polymerization; preferably a temperature of 40 to 80°C; preferably a polymerization time of 2 to 36 hours; preferably a polymerization conversion rate of 50 mass% or more, more preferably 60 mass% or more.

[0118] · Second stage polymerization; preferably a temperature of 40 to 80°C; preferably a polymerization time of 2 to 18 hours.

[0119] By making the total solid content concentration in emulsion polymerization 50 mass% or less, the polymerization reaction can be carried out in a state where the dispersion stability of the particles of the polymer (A) obtained is good. This total solid content concentration is preferably 48 mass% or less, and more preferably 45 mass% or less.

[0120] Whether the synthesis of polymer (A) is carried out as a single-stage polymerization or by a two-stage polymerization method, it is desirable to adjust the pH to approximately 4.5 to 10.5, preferably 5 to 10, and more preferably 5.5 to 9.5 by adding a neutralizing agent to the polymerization mixture after the emulsion polymerization is completed. The neutralizing agent used here is not particularly limited, but examples include metal hydroxides such as sodium hydroxide and potassium hydroxide; ammonia, etc. By setting the pH to the above range, the stability of polymer (A) is improved. After performing the neutralization treatment, the polymerization mixture is concentrated so that the solid content concentration can be increased while maintaining the good stability of polymer (A).

[0121] 1.1.4. Content of polymer (A)

[0122] The content ratio of polymer (A) in the binder composition for a capacitor device according to the present embodiment is preferably 10 to 100 mass% of the polymer component, more preferably 20 to 95 mass%, and particularly preferably 25 to 90 mass%. Here, the polymer component includes polymer (A), a polymer other than polymer (A) described below, and a thickener, etc.

[0123] 1.2. Liquid medium (B)

[0124] The binder composition for a capacitor device according to the present embodiment contains a liquid medium (B). As the liquid medium (B), it is preferable that it be an aqueous medium containing water, and more preferable that it be water. The aqueous medium may contain a non-aqueous medium other than water. Examples of this non-aqueous medium include amide compounds, hydrocarbons, alcohols, ketones, esters, amine compounds, lactones, sulfoxides, sulfone compounds, etc., and one or more selected from these may be used. By using an aqueous medium as the liquid medium (B) in the binder composition for a capacitor device according to the present embodiment, the degree of adverse effect on the environment is reduced, and the safety of handling workers is also increased.

[0125] The content ratio of the non-aqueous medium included in the aqueous medium is preferably 10 mass% or less of the 100 mass% of the aqueous medium, more preferably 5 mass% or less, and particularly preferably not substantially contained. Here, "not substantially contained" means that the non-aqueous medium is not intentionally added as a liquid medium, and may include the non-aqueous medium that is inevitably incorporated when manufacturing the binder composition for the capacitor device.

[0126] 1.3. Other additives

[0127] The binder composition for a capacitor device according to the present embodiment may contain additives other than the components described above as necessary. Examples of such additives include polymers other than polymer (A), preservatives, thickeners, etc.

[0128] 1.3.1. Polymers other than polymer(A)

[0129] The binder composition for a capacitor device according to the present embodiment may contain a polymer other than polymer (A). Examples of such polymers are not particularly limited, but include acrylic polymers containing unsaturated carboxylic acid esters or derivatives thereof as constituent units, and fluorinated polymers such as PVDF (polyvinylidene fluoride). These polymers may be used alone or in combination of two or more types. Including these polymers may further improve flexibility or adhesion.

[0130] 1.3.2. Preservatives

[0131] The binder composition for a capacitor device according to the present embodiment may contain a preservative. By including a preservative, it may be possible to suppress the growth of bacteria, mold, etc., and the occurrence of foreign matter when the binder composition for a capacitor device is stored. Specific examples of preservatives include compounds described in Japanese Patent Publication No. 5477610, etc.

[0132] 1.3.3. Thickeners

[0133] The binder composition for a capacitor device according to the present embodiment may contain a thickener. By including a thickener, the applicability of the slurry and the charge / discharge characteristics of the resulting capacitor device may be further improved.

[0134] Specific examples of thickeners include, for instance, cellulose compounds such as carboxymethylcellulose, methylcellulose, and hydroxypropylcellulose; poly(meth)acrylic acid; ammonium salts or alkali metal salts of the said cellulose compounds or said poly(meth)acrylic acid; polyvinyl alcohol-based (co)polymers such as polyvinyl alcohol, modified polyvinyl alcohol, and ethylene-vinyl alcohol copolymer; and water-soluble polymers such as saponified copolymers of vinyl esters and unsaturated carboxylic acids such as (meth)acrylic acid, maleic acid, and fumaric acid. Among these, alkali metal salts of carboxymethylcellulose and alkali metal salts of poly(meth)acrylic acid are preferred.

[0135] Examples of commercially available thickeners include alkali metal salts of carboxymethylcellulose such as CMC1120, CMC1150, CMC2200, CMC2280, and CMC2450 (all manufactured by Daicel Co., Ltd.).

[0136] When the binder composition for a capacitor device according to the present embodiment contains a thickener, the content ratio of the thickener is preferably 5 mass% or less with respect to 100 mass% of the total solid content of the binder composition for a capacitor device, and more preferably 0.1 to 3 mass%.

[0137] 1.4. pH of binder composition for capacitor devices

[0138] The pH of the binder composition for a capacitor device according to the present embodiment is preferably 5 to 10, more preferably 6 to 9.5, and particularly preferably 6.5 to 9. When the pH is within the above range, the occurrence of problems such as insufficient leveling or liquid sagging can be suppressed, making it easier to manufacture a capacitor device electrode that combines good electrical characteristics and adhesion.

[0139] In this specification, "pH" refers to a physical property measured as follows. It is a value measured in accordance with JIS Z8802:2011 using a pH meter with a glass electrode calibrated with a neutral phosphate standard solution and a borate standard solution as pH standard solutions at 25°C. Examples of such pH meters include the "HM-7J" manufactured by DKK Co., Ltd. and the "D-51" manufactured by Horiba Seisakusho Co., Ltd.

[0140] Furthermore, it should be noted that while the pH of the binder composition for the capacitor device is influenced by the monomer composition constituting the polymer (A), it is not determined solely by the monomer composition. In other words, it is generally known that even with the same monomer composition, the pH of the binder composition for the capacitor device changes due to polymerization conditions, and the examples in this specification merely illustrate one example thereof.

[0141] For example, even with the same monomer composition, the amount of carboxyl groups derived from the unsaturated carboxylic acid exposed on the surface of the resulting polymer differs depending on whether all unsaturated carboxylic acids are added to the polymerization solution from the beginning and other monomers are added sequentially, or whether monomers other than unsaturated carboxylic acids are added first and the unsaturated carboxylic acids are added last. Thus, it is believed that the pH of the binder composition for capacitor devices differs significantly simply by changing the order of monomer addition in the polymerization method.

[0142] 2. Slurry for capacitor devices

[0143] A slurry for a capacitor device according to one embodiment of the present invention contains the aforementioned binder composition for a capacitor device. The aforementioned binder composition for a capacitor device may be used as a material for producing a protective film to suppress short circuits caused by dendrites occurring during charging and discharging, or as a material for producing a capacitor device electrode (active material layer) that improves the bonding ability between active materials, the adhesion ability between the active material and the current collector, and resistance to powder drop. Accordingly, the slurry for a capacitor device for producing a protective film (hereinafter also referred to as the "protective film slurry") and the slurry for a capacitor device for producing an active material layer of a capacitor device electrode (hereinafter also referred to as the "capacitor device electrode slurry") will be described separately.

[0144] 2.1. Slurry for protective film

[0145] "Slurry for protective film" refers to a dispersion used to form a protective film on the surface of an electrode or separator or both thereof by applying it to the surface of the electrode or separator or both thereof and then drying it. The slurry for protective film according to the present embodiment may consist solely of the binder composition for the capacitor device described above, or it may further contain an inorganic filler. Below, each component included in the slurry for protective film according to the present embodiment will be described in detail. Furthermore, the binder composition for the capacitor device is omitted as it is as described above.

[0146] 2.1.1. Weapon Filler

[0147] The protective film slurry according to the present embodiment can improve the toughness of the protective film by containing an inorganic filler. As the inorganic filler, it is preferable to use at least one type of inorganic oxide particle selected from the group consisting of silica, titanium oxide (titania), aluminum oxide (alumina), zirconium oxide (zirconia), and magnesium oxide (magnesia). Among these, titanium oxide particles or aluminum oxide particles are preferred from the view of further improving the toughness of the protective film. Furthermore, as titanium oxide, rutile-type titanium oxide is more preferred.

[0148] The average particle size of the inorganic filler is preferably 1 μm or less, and more preferably 0.1 to 0.8 μm. In addition, the average particle size of the inorganic filler is preferably larger than the average pore diameter of the separator, which is a porous membrane. Accordingly, damage to the separator can be reduced, and the inorganic filler can be prevented from clogging the micropores of the separator.

[0149] In the protective film slurry according to the present embodiment, it is preferable that the binder composition for the capacitor device described above be contained in an amount of 0.1 to 20 parts by weight in terms of solid content relative to 100 parts by weight of inorganic filler, and more preferable that it be contained in an amount of 1 to 10 parts by weight. By having the content ratio of the binder composition for the capacitor device within the above range, the balance between the toughness of the protective film and the permeability of lithium ions is improved, and as a result, the rate of increase in resistance of the capacitor device obtained can be further reduced.

[0150] 2.1.2. Liquid Media

[0151] In the protective film slurry according to the present embodiment, a liquid medium may be additionally added in addition to the portion from the binder composition for the capacitor device. The amount of the liquid medium added can be adjusted as needed so that an optimal slurry viscosity is obtained depending on the coating method, etc. Examples of such liquid mediums include the material described in "1.2. Liquid Medium (B)" above.

[0152] 2.1.3. Other components

[0153] The protective film slurry according to the present embodiment may use an appropriate amount of the materials described in "1.3. Other Additives" as needed.

[0154] 2.2. Slurry for Capacitive Device Electrodes

[0155] "Slurry for capacitor device electrodes" refers to a dispersion liquid used to form an active material layer on the surface of a current collector after applying it to the surface of the current collector and drying it. The capacitor device electrode slurry according to the present embodiment contains the capacitor device binder composition described above and an active material.

[0156] Generally, slurries for capacitor device electrodes often contain a binder component, such as an SBR-based copolymer, and a thickener, such as carboxymethylcellulose, to improve adhesion. Meanwhile, the capacitor device electrode slurry according to the present embodiment can improve adhesion even if it contains only the polymer (A) described above as the polymer component. Of course, the capacitor device electrode slurry according to the present embodiment may contain a polymer other than the polymer (A) or a thickener to further improve adhesion. The components included in the capacitor device electrode slurry according to the present embodiment will be described below.

[0157] 2.2.1. Polymer (A)

[0158] The composition, physical properties, manufacturing method, etc. of the polymer (A) are as described above, so an explanation is omitted.

[0159] The content ratio of the polymer component in the slurry for the electrode of a capacitor device according to the present embodiment is preferably 1 to 8 parts by mass per 100 parts by mass of active material, more preferably 1 to 7 parts by mass, and particularly preferably 1.5 to 6 parts by mass. When the content ratio of the polymer component is within the above range, the dispersibility of the active material in the slurry is improved, and the coating properties of the slurry are also excellent. Here, the polymer component includes a polymer (A), a polymer other than the polymer (A) added as necessary, and a thickener, etc.

[0160] 2.2.2. Active material

[0161] As an active material used in the slurry for the electrode of a capacitor device according to the present embodiment, for example, a carbon material, a silicon material, an oxide containing lithium atoms, a lead compound, a tin compound, an arsenic compound, an antimony compound, an aluminum compound, a conductive polymer such as polyacene, A X B Y O Z Examples include complex metal oxides expressed as (wherein A is an alkali metal or transition metal, B is at least one selected from transition metals such as cobalt, nickel, aluminum, tin, and manganese, O is an oxygen atom, and X, Y, and Z are numbers in the ranges of 1.10 > X > 0.05, 4.00 > Y > 0.85, and 5.00 > Z > 1.5, respectively) or other metal oxides. Specific examples of these include compounds described in Japanese Patent Publication No. 5999399, etc.

[0162] The slurry for capacitor device electrodes according to the present embodiment can be used when manufacturing either the positive electrode or the negative electrode of a capacitor device, and it is preferable to use it on both the positive electrode and the negative electrode.

[0163] When lithium iron phosphate is used as a positive electrode active material, there was a problem in that the charge / discharge characteristics were insufficient and adhesion was poor. It is known that lithium iron phosphate has a fine primary particle size and is a secondary aggregate, and it is thought that one of the factors is that when charging and discharging are repeated, the aggregates within the active material layer collapse, causing a separation between the active materials, which makes it easy for the conductive network inside the active material layer to peel off from the current collector or break.

[0164] The capacitor device electrode produced using the slurry for capacitor device electrodes according to the present embodiment can exhibit good electrical characteristics without the problems described above even when lithium iron phosphate is used as the positive electrode active material. This is thought to be because the polymer (A) can firmly bind lithium iron phosphate and, at the same time, maintain the state of firmly binding lithium iron phosphate even during charging and discharging.

[0165] Meanwhile, when manufacturing a negative electrode, it is preferable to include silicon material among the active materials exemplified above. Since silicon material has a larger lithium absorption capacity per unit weight compared to other active materials, including silicon material as a negative electrode active material can increase the capacitance of the resulting capacitor device, and as a result, increase the output and energy density of the capacitor device.

[0166] In addition, as a negative electrode active material, it is more preferable to use a mixture of silicon material and carbon material. Since the volume change accompanying charging and discharging of carbon material is smaller than that of silicon material, using a mixture of silicon material and carbon material as a negative electrode active material can mitigate the effect of volume change of silicon material, thereby further improving the adhesion ability between the active material layer and the current collector.

[0167] When silicon (Si) is used as an active material, silicon has a high capacity, but it undergoes a large volume change when absorbing lithium. Because of this, silicon materials become finely fragmented due to repeated expansion and contraction, causing delamination from the current collector or separation between active materials, and the conductive network inside the active material layer is prone to breaking. Due to this property, the charge-discharge durability characteristics of the storage device deteriorate drastically in a short period of time.

[0168] The capacitor device electrode produced using the capacitor device electrode slurry according to the present embodiment can exhibit good electrical characteristics without the problems described above even when silicon material is used. This is thought to be because the polymer (A) can firmly bind the silicon material, and at the same time, even if the silicon material expands in volume by absorbing lithium, the polymer (A) can stretch and maintain the state of firmly binding the silicon material.

[0169] The content ratio of silicon material in 100 mass% of the active material is preferably 1 mass% or more, more preferably 2 to 50 mass%, even more preferably 3 to 45 mass%, and particularly preferably 10 to 40 mass%. If the content ratio of silicon material in 100 mass% of the active material is within the above range, a storage device with excellent balance of improved output and energy density and charge / discharge durability characteristics is obtained.

[0170] As for the shape of the active material, it is preferable that it be in the form of particles. As for the average particle size of the active material, it is preferable that it be 0.1 to 100 μm, and more preferable that it be 1 to 20 μm. Here, the average particle size of the active material refers to the volume average particle size calculated from the particle size distribution by measuring the particle size distribution using a particle size distribution measuring device based on the laser diffraction method. Examples of such laser diffraction type particle size distribution measuring devices include the HORIBA LA-300 series and the HORIBA LA-920 series (both manufactured by Horiba Seisakusho Co., Ltd.).

[0171] 2.2.3. Other Components

[0172] In addition to the components described above, other components may be added to the slurry for the electrode of the capacitor device according to the present embodiment. Examples of such components include polymers other than polymer (A), thickeners, liquid media, conductivity-imparting agents, pH adjusters, corrosion inhibitors, cellulose fibers, etc. As polymers other than polymer (A) and thickeners, they may be appropriately selected from the compounds exemplified in "1.3. Other Additives" above and used for the same purpose and in the same proportion.

[0173] Liquid Media

[0174] In addition to the portion from the binder composition for the capacitor device according to the present embodiment, a liquid medium may be further added to the slurry for the capacitor device electrode. The added liquid medium may be of the same type as the liquid medium (B) included in the binder composition for the capacitor device or may be different, but it is preferable to select and use one of the liquid media exemplified in "1.2. Liquid Medium (B)" above.

[0175] In the slurry for an electrode of a capacitor device according to the present embodiment, the content ratio of the liquid medium (including the portion introduced from the binder composition for the capacitor device) is preferably such that the solid content concentration in the slurry (referring to the ratio in which the total mass of components other than the liquid medium in the slurry accounts for the total mass of the slurry; hereinafter the same) is 30 to 70 mass%, and more preferably such that it is 40 to 60 mass%.

[0176] Challenge Granting Ceremony

[0177] In the slurry for the electrode of a capacitor device according to the present embodiment, a conductivity-enhancing agent may be further added for the purpose of imparting conductivity and buffering the volume change of the active material caused by the entry and exit of lithium ions.

[0178] Specific examples of conductive agents include carbons such as activated carbon, acetylene black, ketjen black, furnace black, graphite, carbon fiber, and fullerene. Among these, acetylene black or ketjen black may be preferably used. The content ratio of the conductive agent is preferably 20 parts by weight or less per 100 parts by weight of active material, more preferably 1 to 15 parts by weight, and particularly preferably 2 to 10 parts by weight.

[0179] <pH 조정제·부식 방지제>

[0180] In the slurry for electrodes of a capacitor device according to the present embodiment, a pH adjuster and / or a corrosion inhibitor may be further added for the purpose of suppressing corrosion of the current collector depending on the type of active material.

[0181] Examples of pH adjusting agents include hydrochloric acid, phosphoric acid, sulfuric acid, acetic acid, formic acid, ammonium phosphate, ammonium sulfate, ammonium acetate, ammonium formate, ammonium chloride, sodium hydroxide, potassium hydroxide, etc. Among these, sulfuric acid, ammonium sulfate, sodium hydroxide, and potassium hydroxide are preferred. Additionally, the neutralizing agent described in the method for manufacturing polymer (A) may be selected and used.

[0182] Examples of corrosion inhibitors include ammonium metavanadate, sodium metavanadate, potassium metavanadate, ammonium metatungstate, sodium metatungstate, potassium metatungstate, ammonium paratungstate, sodium paratungstate, potassium paratungstate, ammonium molybdate, sodium molybdate, potassium molybdate, etc., and among these, ammonium paratungstate, ammonium metavanadate, sodium metavanadate, potassium metavanadate, and ammonium molybdate are preferred.

[0183] Cellulose fiber

[0184] Cellulose fibers may be further added to the slurry for the electrode of the capacitor device according to the present embodiment. By adding cellulose fibers, the adhesion of the active material to the current collector may be improved. It is believed that by fibrous cellulose fibers binding adjacent active materials together in a fibrous manner through linear adhesion or linear contact, the detachment of the active material can be prevented, and the adhesion to the current collector can be improved.

[0185] The average fiber length of the cellulose fiber can be selected from a wide range of 0.1 to 1000 μm, and, for example, preferably 1 to 750 μm, more preferably 1.3 to 500 μm, even more preferably 1.4 to 250 μm, and particularly preferably 1.8 to 25 μm. When the average fiber length is within the above range, the surface smoothness (film uniformity) is improved, and the adhesion of the active material to the current collector may be improved.

[0186] The fiber length of the cellulose fiber may be uniform, and the coefficient of variation of the fiber length ([standard deviation of fiber length / average fiber length] × 100) is, for example, preferably 0.1 to 100, more preferably 0.5 to 50, and particularly preferably 1 to 30. The maximum fiber length of the cellulose fiber is, for example, preferably 500 μm or less, more preferably 300 μm or less, even more preferably 200 μm or less, even more preferably 100 μm or less, and particularly preferably 50 μm or less.

[0187] If the average fiber length of the cellulose fiber is reduced to five times or less the average thickness of the active material layer, it is advantageous because the surface smoothness (film uniformity) and the adhesion of the active material to the current collector are further improved. The average fiber length of the cellulose fiber is preferably 0.01 to 5 times, more preferably 0.02 to 3 times, and particularly preferably 0.03 to 2 times the average thickness of the active material layer.

[0188] The average fiber diameter of the cellulose fiber is preferably 1 nm to 10 µm, more preferably 5 nm to 2.5 µm, even more preferably 20 nm to 700 nm, and particularly preferably 30 nm to 200 nm. When the average fiber diameter is within the above range, the volume occupied by the fiber does not become too large, and the packing density of the active material can be increased. For this reason, it is preferable that the cellulose fiber be a nanometer-sized cellulose nanofiber with an average fiber diameter (for example, a cellulose nanofiber with an average fiber diameter of 10 nm to 500 nm, preferably 25 nm to 250 nm).

[0189] The fiber diameter of the cellulose fiber is also uniform, and the coefficient of variation of the fiber diameter ([standard deviation of fiber diameter / average fiber diameter] × 100) is preferably 1 to 80, more preferably 5 to 60, and particularly preferably 10 to 50. The maximum fiber diameter of the cellulose fiber is preferably 30 μm or less, more preferably 5 μm or less, and particularly preferably 1 μm or less.

[0190] The ratio of the average fiber length to the average fiber diameter of the cellulose fiber (aspect ratio) is, for example, preferably 10 to 5000, more preferably 20 to 3000, and particularly preferably 50 to 2000. When the aspect ratio is within the above range, the adhesion of the active material to the current collector is improved, and the breaking strength of the fiber is not weakened, so the surface smoothness (film uniformity) of the electrode may be improved.

[0191] In the present invention, the average fiber length, the standard deviation of the fiber length distribution, the maximum fiber length, the average fiber diameter, the standard deviation of the fiber diameter distribution, and the maximum fiber diameter may be values ​​calculated from fibers (n=20) measured based on electron microscope images.

[0192] The material of the cellulose fiber may be formed from a polysaccharide having a β-1,4-glucan structure. As cellulose fibers, natural cellulose fibers (pulp fibers) such as, for example, cellulose fibers derived from higher plants (e.g., wood fibers (wood pulp of conifers, hardwoods, etc.), bamboo fibers, sugarcane fibers, seed hair fibers (e.g., cotton linter, bombax cotton, kapok, etc.), dermal fibers (e.g., hemp, paper mulberry, Daphne, etc.), leaf fibers (e.g., Manila hemp, New Zealand hemp, etc.), cellulose fibers derived from animals (e.g., hoya cellulose), cellulose fibers derived from bacteria (e.g., cellulose contained in nata de coco), chemically synthesized cellulose fibers (e.g., rayon, cellulose esters (cellulose acetate, etc.), cellulose ethers (e.g., hydroxyalkylcellulose such as hydroxyethylcellulose (HEC) and hydroxypropylcellulose), and alkylcellulose such as methylcellulose and ethylcellulose). Examples include etc. These cellulose fibers may be used as a single type or in combination of two or more types.

[0193] Among these cellulose fibers, cellulose fibers derived from higher plants, such as wood fibers (wood pulp of conifers, hardwoods, etc.) or seed fibers (cotton linter pulp, etc.), are preferred because it is easy to prepare nanofibers having a suitable aspect ratio.

[0194] The method for manufacturing cellulose fibers is not particularly limited, and depending on the desired fiber length and fiber diameter, conventional methods may be used, for example, methods described in Japanese Patent Publication No. 60-19921, Japanese Patent Publication No. 2011-26760, Japanese Patent Publication No. 2012-25833, Japanese Patent Publication No. 2012-36517, Japanese Patent Publication No. 2012-36518, Japanese Patent Publication No. 2014-181421, etc.

[0195] 2.2.4. Method for preparing a slurry for capacitor device electrodes

[0196] The slurry for an electrode of a capacitor device according to the present embodiment may be prepared by any method as long as it contains the capacitor device binder composition and active material described above. In order to produce a slurry having better dispersibility and stability more efficiently and at a lower cost, it is preferable to prepare the slurry by adding an active material and optional additive components used as needed to the capacitor device binder composition and mixing them. Specific manufacturing methods include, for example, the method described in Japanese Patent Publication No. 5999399.

[0197] 3. Capacitor Device Electrode

[0198] A capacitor device electrode according to one embodiment of the present invention comprises a current collector and an active material layer formed by applying and drying the aforementioned slurry for capacitor device electrodes on the surface of the current collector. Such a capacitor device electrode can be manufactured by applying the aforementioned slurry for capacitor device electrodes to the surface of a current collector, such as a metal foil, to form a coating film, and then drying the coating film to form an active material layer. Since the capacitor device electrode manufactured in this manner is formed by bonding an active material layer containing the aforementioned polymer (A), an active material, and optionally added components to the surface of the current collector, it has excellent repetitive charge / discharge characteristics and excellent charge / discharge durability characteristics under high temperatures.

[0199] As for the current collector, it is not particularly limited as long as it includes a conductive material, but for example, the current collector described in Japanese Patent Publication No. 5999399 can be cited.

[0200] In the capacitor device electrode according to the present embodiment, when a silicon material is used as the active material, the content ratio of silicon elements in 100 mass% of the active material layer is preferably 2 to 30 mass%, more preferably 2 to 20 mass%, and particularly preferably 3 to 10 mass%. If the content of silicon elements in the active material layer is within the above range, in addition to improving the capacitance of the capacitor device manufactured using it, an active material layer with a uniform distribution of silicon elements is obtained. The content of silicon elements in the active material layer can be measured by a method described, for example, in Japanese Patent Publication No. 5999399.

[0201] 4. Storage device

[0202] A capacitor device according to one embodiment of the present invention may be manufactured according to a conventional method by providing the capacitor device electrode described above, additionally containing an electrolyte, and using components such as a separator. Specific manufacturing methods include, for example, overlapping a negative electrode and a positive electrode with a separator interposed therebetween, winding or folding them according to the battery shape to house them in a battery container, and injecting an electrolyte into the battery container and sealing it. The shape of the battery may be a suitable shape, such as a coin type, cylindrical type, prismatic type, or laminate type.

[0203] The electrolyte may be in a liquid or gel form, and depending on the type of active material, one that effectively exhibits the function of a battery may be selected from among the known electrolytes used in storage devices. The electrolyte may be a solution in which an electrolyte is dissolved in a suitable solvent. Examples of such electrolytes or solvents include compounds described in Japanese Patent Publication No. 5999399, etc.

[0204] The above-described energy storage device can be applied to lithium-ion secondary batteries, electric double-layer capacitors, lithium-ion capacitors, etc., which require discharge at high current densities. Among these, lithium-ion secondary batteries are particularly preferred. In the energy storage device electrode and energy storage device according to the present embodiment, for the components other than the binder composition for the energy storage device, it is possible to use known components for lithium-ion secondary batteries, electric double-layer capacitors, or lithium-ion capacitors.

[0205] 5. Examples

[0206] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. In the examples and comparative examples, "parts" and "%" are based on mass unless otherwise specified.

[0207] 5.1. Example 1

[0208] 5.1.1. Preparation and Evaluation of Physical Properties of Binder Compositions for Capacitive Devices

[0209] (1) Preparation of a binder composition for a capacitor device

[0210] A binder composition for a capacitor device containing polymer (A) was obtained by a two-stage polymerization as described below. A monomer mixture comprising 200 parts by mass of water, 15 parts by mass of 1,3-butadiene, 15 parts by mass of styrene, and 2 parts by mass of acrylic acid, 0.1 parts by mass of tert-dodecyl mercaptan as a chain transfer agent, 0.2 parts by mass of sodium alkyl diphenyl ether disulfonate as an emulsifier, and 0.2 parts by mass of potassium persulfate as a polymerization initiator were added to a reactor, and polymerization was carried out at 70°C for 12 hours while stirring, after which it was confirmed that the polymerization conversion rate was 90%. Next, 200 parts by mass of water, 55 parts by mass of styrene, 3 parts by mass of acrylic acid, 5 parts by mass of methyl methacrylate, and 5 parts by mass of acrylonitrile were added to a reactor, and polymerization was carried out at 75°C for 12 hours, after which it was confirmed that the polymerization conversion rate was 98%. Unreacted monomers were removed from the particle dispersion of polymer (A) obtained in this way and concentrated, and after adding a 2.5% aqueous sodium hydroxide solution, moisture was removed using an evaporator, thereby obtaining a binder composition for a capacitor device containing particles of polymer (A) having a solid content concentration of 40% by mass and a pH of 8.0.

[0211] (2) Measurement of number average particle size

[0212] A sample was prepared by pipetting one drop of latex diluted to 0.1 wt% of the binder composition for capacitor devices obtained above onto a collodion film, additionally pipetting one drop of a 0.02 wt% osmium tetraoxide solution onto the collodion film, and air-drying for 12 hours. The sample prepared in this manner was observed at a magnification of 10K using a transmission electron microscope (TEM, manufactured by Hitachi High Technologies Co., Ltd., model number “H-7650”), image analysis was performed using the HITACHI EMIP program, and the number-average particle size of 50 randomly selected polymer (A) particles was calculated. The measurement results are shown in Table 1.

[0213] (3) Measurement of pH

[0214] Regarding the binder composition for the capacitor device obtained above, the pH at 25°C was measured using a pH meter (manufactured by Horiba Seisakusho Co., Ltd.) and it was confirmed to be pH 8.0.

[0215] (4) Measurement of electrolyte swelling degree

[0216] A film was prepared by drying the polymer (A) obtained above in a constant temperature bath at 85°C for 24 hours. 1 g of this film was immersed in 20 mL of a mixture containing ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) (EC / DEC / EMC = 1 / 1 / 1 (volume ratio), hereinafter referred to as "EC / DEC / EMC") and shaken at 70°C for 24 hours. Subsequently, the insoluble matter was separated by filtration using a 300-mesh metal mesh, and the EC / DEC / EMC of the dissolved matter was removed by evaporation, and the weight (Y(g)) of the remaining matter obtained was measured. In addition, the EC / DEC / EMC attached to the surface of the insoluble matter (film) separated by the above filtration was removed by absorbing it into paper, and the weight (Z(g)) of the insoluble matter (film) was measured. When the degree of electrolyte swelling was measured by the following formula (2), the degree of electrolyte swelling of the polymer (A) was 160 mass%.

[0217] Electrolyte swelling degree (mass%) = (Z / (1-Y)) × 100 (2)

[0218] (5) Measurement of dynamic viscoelasticity

[0219] The polymer (A) obtained above was dried at 40°C for 24 hours to produce a uniform film with a thickness of 1.0 ± 0.3 mm. This film was dried in a vacuum dryer at 160°C for 30 minutes. The film was removed from the vacuum dryer and cut into a 10 mm × 10 mm rectangular shape to serve as a sample for measurement. Subsequently, using a dynamic viscoelasticity measuring device (manufactured by Anton Paar, model "MCR 301"), the sample for measurement was fixed to a parallel plate (product name "PP-12"), and dynamic viscoelasticity was measured in a temperature range of -70°C to 180°C under measurement conditions of shear mode, measurement frequency of 0.01 to 1 Hz, and heating speed of 0.1°C / min. As a result, the peak top of tanδ on the low-temperature side (tanδ-1) was observed at 10°C, and the value was 0.02. In addition, the peak top of tanδ on the high temperature side (tanδ-2) was observed at 120°C, and the value was 1.0. Also, in Tables 1 to 3 below, the peak top of tanδ on the low temperature side is indicated as "tanδ-1", and tanδ on the high temperature side is indicated as "tanδ-2".

[0220] (6) Measurement of Martens Hardness

[0221] About 1 g of the polymer (A) obtained above was added to a Si wafer of about 1 cm × 1 cm, and a thin film was fabricated using spin coating (manufactured by Mikasa Co., Ltd., model “MS-A-150”) and dried on a hot plate. The Martens hardness of this thin film was calculated using a picoindenter (manufactured by Helmut Fischer, model “HM500”) and was 300 MPa.

[0222] 5.1.2. Preparation of slurry for capacitor device electrodes

[0223] (1) Synthesis of silicon materials (active materials)

[0224] A mixture of ground silicon dioxide powder (average particle size 10 μm) and carbon powder (average particle size 35 μm) is subjected to heat treatment for 10 hours under a nitrogen stream (0.5 NL / min) in an electric furnace adjusted to a temperature range of 1100°C to 1600°C, thereby producing SiO₂ with compositional formula x Silicon oxide powder (average particle size 8 μm) expressed as (x=0.5 to 1.1) was obtained. 300 g of this silicon oxide powder was introduced into a batch furnace, and while maintaining a reduced pressure of 100 Pa by a vacuum pump, the temperature was raised from room temperature (25°C) to 1100°C at a heating rate of 300°C / h. Subsequently, while maintaining the pressure inside the furnace at 2000 Pa and introducing methane gas at a flow rate of 0.5 NL / min, a heat treatment (graphite coating treatment) was performed at 1100°C for 5 hours. After the graphite coating treatment was completed, the powder was cooled to room temperature at a cooling rate of 50°C / h, thereby obtaining approximately 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 size is 10.5 μm, and the proportion of the graphite film when the total of the obtained graphite-coated silicon oxide is 100 mass% was 2 mass%.

[0225] (2) Preparation of a slurry for electrodes of capacitor devices

[0226] In a twin-axis planetary mixer (manufactured by Primix Co., Ltd., product name "TK Hybis Mix 2P-03"), 1 mass part of a thickener (product name "CMC2200", manufactured by Daicel Co., Ltd.) (converted to solid content, added as an aqueous solution with a concentration of 2 mass%), 4 mass parts of polymer (A) (converted to solid content, added as a binder composition for capacitor devices obtained above), 90.25 mass parts of artificial graphite (manufactured by Showa Denko Materials Co., Ltd., product name "MAG"), which is highly crystalline graphite, as a negative electrode active material (converted to solid content), 4.75 mass parts of the silicon oxide powder with a graphite coating obtained above (converted to solid content), and 1 mass part of carbon (manufactured by Denka Co., Ltd., acetylene black) as a conductivity imparter were added, and at 60 rpm A paste was obtained by stirring for 1 hour. Water was added to the obtained paste to adjust the solid content to 48 mass%, and then, using a stirred degassing machine (manufactured by Shinki Co., Ltd., trade name "Awatori Rentaro"), the process was carried out at 200 rpm for 2 minutes, at 1800 rpm for 5 minutes, and then under reduced pressure (approx. 2.5 × 10⁻⁶ 4 A slurry for capacitor device electrodes (C / Si=95 / 5) containing 5 mass% of Si in the negative electrode active material was prepared by stirring and mixing at 1800 rpm for 1.5 minutes in Pa).

[0227] In addition, a slurry for an electrode for a capacitor device (C / Si=100 / 0) that does not contain Si in the negative electrode active material was prepared in the same way as the slurry for an electrode for a capacitor device (C / Si=95 / 5), except for adjusting the amount of powder used for artificial graphite and silicon oxide coated on the graphite film.

[0228] 5.1.3. Manufacture and Evaluation of Storage Devices

[0229] (1) Manufacturing of a capacitor device electrode (negative electrode)

[0230] The capacitor device electrode slurry (C / Si=95 / 5 or C / Si=100 / 0) obtained above was uniformly applied to the surface of a current collector containing a copper foil with a thickness of 20 μm using the doctor blade method so that the film thickness after drying was 80 μm, dried at 60°C for 10 minutes, and then dried at 120°C for 10 minutes. After that, the density of the active material layer was 1.5 g / cm³ 3 By press processing with a roll press machine to achieve this, a capacitor device electrode (negative electrode) was obtained.

[0231] (2) Evaluation of the adhesion strength of the negative electrode coating layer

[0232] On the surface of the capacitor device electrode obtained above, a checkerboard pattern of cuts was created by using a knife to make 10 cuts each in the longitudinal and transverse directions at 2mm intervals, extending from the active material layer to the depth reaching the current collector. An adhesive tape with a width of 18mm (manufactured by Nichiban Corporation, product name "Cello Tape" (registered trademark), specified in JIS Z1522) was applied to these cuts and immediately peeled off. The degree of detachment of the active material was evaluated by visual inspection. The evaluation criteria are as follows. The evaluation results are shown in Table 1.

[0233] (metewand)

[0234] · 5 points: 0 sheddings of the active material layer.

[0235] · 4 points: 1 to 5 sheddings of the active material layer.

[0236] · 3 points: The shedding of the active material layer is 6 to 20.

[0237] · 2 points: The shedding of the active material layer is 21 to 40.

[0238] · 1 point: There are 41 or more sheddings of the active material layer.

[0239] (3) Preparation of the counter electrode (positive electrode)

[0240] 4 parts by mass (solid content equivalent) of a binder for electrochemical device electrodes (manufactured by Kureha Co., Ltd., product name “TK Hibis Mix 2P-03”), 3.0 parts by mass of a conductivity aid (manufactured by Denka Co., Ltd., product name “Denka Black 50% Pressed Product”), 100 parts by mass (solid content equivalent) of LiCoO2 with an average particle size of 5 μm (manufactured by Hayashi Kasei Co., Ltd.) as a positive electrode active material, and 36 parts by mass of N-methylpyrrolidone (NMP) were added, and stirring was performed at 60 rpm for 2 hours. After adding NMP to the obtained paste to adjust the solid content to 65 mass%, a stirred degassing machine (manufactured by Shinki Co., Ltd., trade name "Awatori Rentaro") was used, and the process was carried out at 200 rpm for 2 minutes, at 1800 rpm for 5 minutes, and additionally under reduced pressure (approx. 2.5 × 10⁻⁶ 4 A positive electrode slurry was prepared by stirring and mixing at 1800 rpm for 1.5 minutes in Pa. This positive electrode slurry was uniformly applied to the surface of a current collector containing aluminum foil using the 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. Subsequently, the density of the active material layer was 3.0 g / cm³ 3 A counter electrode (positive electrode) was obtained by press processing using a roll press machine.

[0241] (4) Assembly of lithium-ion battery cells

[0242] In a glove box substituted with Ar so that the dew point is -80°C or lower, the negative electrode prepared above was punched and molded to a diameter of 15.95 mm and loaded onto a two-electrode coin cell (manufactured by Hosen Co., Ltd., product name "HS Flat Cell"). Subsequently, a separator (manufactured by Cell Guard Co., Ltd., product name "Cell Guard #2400") containing a polypropylene porous membrane punched to a diameter of 24 mm was loaded, and 500 μL of electrolyte was injected to prevent air from entering. Then, the positive electrode prepared above was punched and molded to a diameter of 16.16 mm and loaded, and the outer body of the two-electrode coin cell was closed with screws to seal it, thereby assembling a lithium-ion battery cell (energy storage device). The electrolyte used here is a solution in which LiPF6 is dissolved at a concentration of 1 mol / L in a solvent of ethylene carbonate / ethylmethyl carbonate = 1 / 1 (mass ratio).

[0243] (5) Evaluation of charge / discharge cycle characteristics

[0244] For the capacitor device manufactured above, charging was started with a constant current (1.0C) in a constant temperature bath heated to 60°C, and charging was continued at a constant voltage (4.2V) when the voltage reached 4.2V, and the point at which the current value became 0.01C was set as the completion of charging (cutoff). Afterward, discharging was started with a constant current (1.0C), and the point at which the voltage reached 3.0V was set as the completion of discharging (cutoff), and the discharge capacity of the first cycle was calculated. In this way, 100 charge-discharge cycles were repeated. The capacity retention rate was calculated using the following equation (3) and evaluated according to the following criteria. The evaluation results are shown in Table 1.

[0245] Capacity retention rate (%)

[0246] =(Discharge capacity at the 100th cycle) / (Discharge capacity at the 1st cycle) (3)

[0247] (metewand)

[0248] · 5 points: Dose retention rate of 95% or higher.

[0249] · 4 points: Dose retention rate of 90% or more to less than 95%.

[0250] · 3 points: Dose retention rate of 85% or more to less than 90%.

[0251] · 2 points: Dose retention rate of 80% or more to less than 85%.

[0252] · 1 point: Dose retention rate of 75% or more to less than 80%.

[0253] · 0 points: Dose retention rate less than 75%.

[0254] (6) Evaluation of resistance at high temperatures

[0255] For the capacitor device manufactured above, charging was started with a constant current (1.0C) in a constant temperature bath heated to 60°C, and charging was continued at a constant voltage (4.2V) when the voltage reached 4.2V, and the point at which the current value became 0.01C was set as the point of completion of charging (cutoff). After that, discharging was started with a constant current (0.05C), and the point at which the voltage reached 3.0V was set as the point of completion of discharging (cutoff), and the discharge capacity of the 0th cycle was calculated. Additionally, charging was started with a constant current (1.0C), and charging was continued at a constant voltage (4.2V) when the voltage reached 4.2V, and the point at which the current value became 0.01C was set as the point of completion of charging (cutoff). After that, discharging was started with a constant current (1.0C), and the point at which the voltage reached 3.0V was set as the point of completion of discharging (cutoff), and the discharge capacity of the 1st cycle was calculated. In this way, 100 charge-discharge cycles were repeated. After repeating 100 charge-discharge cycles, charge-discharge was performed in the same manner as in the 0th cycle, the discharge capacity of the 101st cycle was evaluated, the resistance increase rate was calculated by the following equation (4), and evaluated according to the following criteria.

[0256] Resistance rise rate (%)

[0257] =(Discharge capacity at cycle 101 - Discharge capacity at cycle 100) / (Discharge capacity at cycle 0 - Discharge capacity at cycle 1)×100 (4)

[0258] (metewand)

[0259] · 5 points: Resistance rise rate of 100% or more to less than 150%.

[0260] · 4 points: Resistance rise rate of 150% or more to less than 200%.

[0261] · 3 points: Resistance rise rate of 200% or more to less than 250%.

[0262] · 2 points: Resistance rise rate of 250% or more to less than 300%.

[0263] · 1 point: Resistance rise rate of 300% or more to less than 350%.

[0264] · 0 points: Resistance rise rate of 350% or more.

[0265] In addition, regarding measurement conditions, “1C” refers to a current value at which the discharge of a cell having a certain electrical capacity is terminated in 1 hour by constant current discharge. For example, “0.1C” refers to a current value at which the discharge is terminated over 10 hours, and “10C” refers to a current value at which the discharge is terminated over 0.1 hours.

[0266] 5.2. Examples 2 to 12, Comparative Examples 1 to 5

[0267] In the above “5.1.1. Preparation of binder composition for capacitor device and evaluation of physical properties (1) Preparation of binder composition for capacitor device,” except that the type and amount of each monomer and the amount of emulsifier were as described in Tables 1 to 3 below, respectively, binder compositions for capacitor devices containing polymer particles with a solid content concentration of 40 mass% were obtained, and each physical property was evaluated. In addition, FIG. 1 shows a graph showing the relationship between the measurement temperature and tanδ in the dynamic viscoelasticity measurement of the film prepared in Example 3.

[0268] In addition, a slurry for a capacitor device electrode was prepared in the same manner as in Example 1, except that the binder composition for a capacitor device prepared above was used, and a capacitor device electrode and a capacitor device were manufactured and evaluated in the same manner as in Example 1.

[0269] 5.3. Example 13

[0270] In Example 4, a slurry for an electrode for a capacitor device was prepared in the same manner as in Example 4, except that the thickener was 0.9 parts by mass of CMC (product name "CMC2200", manufactured by Daicel Co., Ltd., fiber diameter 0.07 μm) and 0.1 parts by mass of CNF (product name "Selish KY-100G", manufactured by Daicel Co., Ltd., fiber diameter 0.07 μm). The capacitor device electrode and the capacitor device were each fabricated and evaluated in the same manner as in Example 1. The results are shown in Table 4 below.

[0271] 5.4. Example 14

[0272] In Example 4, a slurry for an electrode for a capacitor device was prepared in the same manner as in Example 4, except that the thickener was 0.8 parts by mass of CMC (product name "CMC2200", manufactured by Daicel Co., Ltd., fiber diameter 0.07 μm) and 0.2 parts by mass of CNF (product name "Selish KY-100G", manufactured by Daicel Co., Ltd., fiber diameter 0.07 μm). The capacitor device electrode and the capacitor device were each fabricated and evaluated in the same manner as in Example 1. The results are shown in Table 4 below.

[0273] 5.5. Evaluation Results

[0274] Tables 1 to 3 below show the polymer compositions used in Examples 1 to 12 and Comparative Examples 1 to 5, the results of each physical property measurement, and each evaluation result. Table 4 below shows the polymer component compositions used in Examples 13 and 14 and each evaluation result.

[0275]

[0276]

[0277]

[0278]

[0279] The abbreviations for monomers and thickeners in Tables 1 to 4 above each represent the following compounds.

[0280] Conjugated diene compounds

[0281] ·BD: 1,3-butadiene

[0282] Unsaturated Carboxylic Acid

[0283] ·TA: Itaconic acid

[0284] ·AA: Acrylic acid

[0285] ·MAA: Methacryl acid

[0286] Aromatic vinyl compounds

[0287] ·ST: Styrene

[0288] ·DVB: Divinylbenzene

[0289] Unsaturated Carboxylic Acid Ester

[0290] ·MMA: Methyl methacrylate

[0291] ·BA: Butyl acrylate

[0292] ·2EHA: 2-ethylhexyl acrylic acid

[0293] ·CHMA: Cyclohexyl methacrylate

[0294] · EDMA: Ethylene glycol dimethacrylate

[0295] ·HEMA: 2-hydroxyethyl methacrylate

[0296] ·HEA: 2-hydroxyethyl acrylic acid

[0297] <α,β-unsaturated nitrile compounds>

[0298] ·AN: Acrylonitrile

[0299] <(Met)acrylamide>

[0300] ·AAM: Acrylamide

[0301] ·MAM: Methacrylamide

[0302] Compounds having a sulfonic acid group

[0303] ·NASS: Sodium styrenesulfonate

[0304] Thickener

[0305] ·CMC: Product name "CMC2200", manufactured by Daicel Co., Ltd., sodium carboxymethylcellulose

[0306] · CNF: Product name "Selish KY-100G", manufactured by Daicel Co., Ltd., microfibrous cellulose, fiber diameter 0.07㎛

[0307] As is evident from Tables 1 to 2 above, the slurry for a capacitor device electrode prepared using the binder composition for a capacitor device according to the present invention shown in Examples 1 to 12 can suitably bind the active materials together and suppress the fusion of particles within the electrode compared to Comparative Examples 1 to 5, thereby reducing internal resistance and obtaining a capacitor device electrode having good charge / discharge durability characteristics at high temperatures. The reason for this is that the polymer (A) contained in the binder composition of Examples 1 to 12 shown in Tables 1 to 2 has one temperature Tp (°C) of the tanδ-1 peak top in the range of -40°C or higher and less than 50°C compared to Comparative Examples 1 to 5 shown in Table 3, which suggests that the viscosity is high. Accordingly, it is presumed that high binding strength can be maintained. In addition, the temperature Tp (°C) of the peak top of tanδ-2 of the polymer (A) exists in the range of 50°C to 150°C, which suggests that the degree of crosslinking of the polymer on the high-temperature side is higher. As a result, it is possible to maintain the particle shape of the binder when making the electrode. Accordingly, the penetration of the electrolyte between the active materials is not hindered, so low resistance can be achieved, and as a result, it is presumed that good repeated charge-discharge characteristics and good charge-discharge durability characteristics at high temperatures were exhibited.

[0308] In addition, as is evident from the results of Table 4 above, it was found that the slurry for capacitor device electrodes prepared using the binder composition for capacitor devices according to the present invention shown in Examples 13 and 14 can suitably bind active materials together even when CNF is used as a thickener, and furthermore, can maintain good adhesion between the active material layer and the current collector.

[0309] The present invention is not limited to the embodiments described above, but allows for various modifications. The present invention includes a configuration substantially identical to the configuration described in the embodiments (e.g., a configuration with the same function, method, and result, or a configuration with the same purpose and effect). Furthermore, the present invention includes a configuration in which non-essential parts of the configuration described in the embodiments are replaced with other configurations. Additionally, the present invention includes a configuration capable of producing the same functional effect or achieving the same purpose as the configuration described in the embodiments. Furthermore, the present invention includes a configuration in which known technology is added to the configuration described in the embodiments.

Claims

Claim 1 A binder for a capacitor device comprising a polymer (A) and a liquid medium (B), wherein when the total number of repeating units included in the polymer (A) is 100 mass%, the polymer (A) processing liquid contains 15 to 60 mass% of repeating units (a1) derived from a diene compound and 1 to 10 mass% of repeating units (a2) derived from an unsaturated carboxylic acid, wherein the peak tops of the dynamic viscoelasticity tanδ (loss modulus / storage modulus) of the polymer (A) are one in the range of -40°C or higher and less than 50°C, and one in the range of 50°C or higher and less than 150°C, and when the tanδ of the peak top in the range of -40°C or higher and less than 50°C is denoted as tanδ(Tp1) and the tanδ of the peak top in the range of 50°C or higher and less than 150°C is denoted as tanδ(Tp2), the binder satisfies the relationship of the following formula (1). Composition.tanδ(Tp2) / tanδ(Tp1)≥0.5 (1) Claim 2 A binder composition for a capacitor device according to claim 1, wherein the polymer (A) further contains 35 to 75 mass% of a repeating unit (a3) ​​derived from an aromatic vinyl compound, and the total amount of the repeating unit (a1), the repeating unit (a2), and the repeating unit (a3) ​​is 80 mass% or more. Claim 3 A binder composition for a capacitor device according to claim 1, wherein the polymer (A) contains at least one of a repeating unit (a4) derived from an unsaturated carboxylic acid ester and a repeating unit (a5) derived from an α,β-unsaturated nitrile compound, and the total amount of the repeating unit (a1), the repeating unit (a2), the repeating unit (a4) and the repeating unit (a5) is 65 mass% or more. Claim 4 A binder composition for a capacitor device according to claim 1, wherein the martens hardness calculated using the picoindenter of the polymer (A) is 15 MPa or higher. Claim 5 A binder composition for a capacitor device according to claim 1, wherein the polymer (A) is a polymer particle, and the number average particle size of the polymer particle is 50 nm or more and 500 nm or less. Claim 6 A binder composition for a capacitor device according to claim 1, wherein the liquid medium (B) is water. Claim 7 A binder composition for a capacitor device described in any one of claims 1 to 6, and a slurry for a capacitor device electrode containing an active material. Claim 8 A slurry for an electrode of a capacitor device containing a silicon material as the active material in claim 7. Claim 9 A capacitor device electrode comprising a current collector and an active material layer formed by applying and drying a slurry for a capacitor device electrode described in claim 7 on the surface of the current collector. Claim 10 A capacitor device having the capacitor device electrode described in paragraph 9.

Images