JP2010040228A - Binder composition for energy device electrode, slurry for the energy device electrode, energy device electrode, and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: a binder composition for an energy device electrode, which has high adhesiveness to a collector and can form an electrode layer excellent in press workability; a slurry for an energy device electrode; and an energy device electrode that can be obtained using the slurry. <P>SOLUTION: The binder composition for the energy device electrode contains a polymer latex containing 70% or more toluene gel. The number-based particle size distribution of the polymer latex as measured by laser diffractometry has peaks in the range of 80-120 nm and in the range of 150-280 nm, and has peaks indicating glass transition temperatures in the range of 5 to 50°C and in the range of -50 to 0°C when measured using a differential scanning calorimeter. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention provides a binder composition for obtaining an electrode of an energy device such as a secondary battery, an electric double layer capacitor, or a lithium ion capacitor, a slurry for an energy device electrode containing the binder composition, and a slurry obtained using the slurry. The present invention relates to an energy device electrode and a manufacturing method thereof.

2. Description of the Related Art In recent years, progress in downsizing and weight reduction of electronic devices has been remarkable, and accordingly, demands for downsizing and weight reduction of batteries used as power sources for driving the electronic devices have further increased. In order to satisfy such demands for reduction in size and weight, various secondary batteries have been developed in the past, such as nickel metal hydride secondary batteries and lithium ion secondary batteries.
Thus, as a method of manufacturing the electrodes constituting these secondary batteries, active materials such as hydrogen storage alloys and graphite, thickeners such as carboxymethylcellulose, and binders such as styrene-butadiene copolymer latex are used. A method of forming an electrode layer by applying a paste or slurry in which water is dispersed in water to the surface of a current collector and drying, and pressing the resulting coating film is known (for example, (See Patent Literature 1 and Patent Literature 2).
Here, in addition to the function of binding the active material, the binder has a function of improving the adhesion between the electrode layer containing the active material and the current collector.

However, when a highly adhesive material is used as a binder to improve adhesion, the resulting electrode layer has a migration of the binder, resulting in a sticky surface of the electrode layer and reduced press workability. There is a problem. On the other hand, in a secondary battery using an electrode in which the adhesion between the electrode layer and the current collector is not sufficient, there is a problem that battery characteristics such as charge / discharge cycle characteristics cannot be improved.
In addition, there is known a method of forming an electrode in which a plurality of electrode layers are laminated using pastes having different compositions (see, for example, Patent Document 3 and Patent Document 4). There is a drawback that the process becomes complicated.

Japanese Patent Laid-Open No. 11-7948 Japanese Patent Laid-Open No. 2001-210318 JP-A-9-134718 JP 2004-127590 A

  The present invention has been made based on the circumstances as described above, and an object thereof is an energy device that can form an electrode layer having high adhesion to a current collector and excellent in press workability. It is providing the binder composition for electrodes, the slurry for energy device electrodes, the energy device electrode obtained using this slurry, and its manufacturing method.

The binder composition for an energy device electrode of the present invention comprises a polymer latex having a toluene gel content of 70% or more,
The polymer latex has a number-based particle size distribution measured by a laser diffraction method having a peak in each of 80 to 120 nm and 150 to 280 nm, and a differential scanning calorimeter. It has a peak showing a glass transition temperature in each of the range of 5 to 50 ° C. and the range of −50 to 0 ° C.

The binder composition for energy device electrodes of the present invention has a polymer latex (a) having a number average particle size of 80 to 120 nm, a glass transition temperature of 5 to 50 ° C., and a toluene gel content of 70% or more,
It is characterized by comprising a polymer latex (b) having a number average particle size of 150 to 280 nm, a glass transition temperature of −50 ° C. to 0 ° C., and a toluene gel content of 70% or more.

In the binder composition for an energy device electrode of the present invention, each of the polymer latex (a) and the polymer latex (b) is composed of a monomer (I) composed of an aromatic vinyl compound and an aliphatic conjugated diene compound. Obtained by emulsion polymerization of a monomer (II) comprising an ethylenically unsaturated carboxylic acid (III) and a monomer (IV) comprising another vinyl compound copolymerizable therewith. It is preferably made of a copolymer.
Moreover, it is preferable to contain (mass) acrylonitrile 10 mass% or more of all the monomers as monomer (I) for obtaining polymer latex (a).

The slurry for energy device electrodes of the present invention comprises the above-mentioned binder composition for energy device electrodes,
It is characterized by containing an electrode active material.

  In the slurry for energy device electrodes of this invention, it is preferable that solid content in the binder composition for energy device electrodes is contained in the ratio of 0.1-10 mass parts with respect to 100 mass parts of electrode active materials.

The energy device electrode of the present invention comprises a current collector,
An electrode layer formed by applying and drying the slurry for a secondary battery electrode on the surface of the current collector is provided.

  The manufacturing method of the energy device electrode of this invention has the process of apply | coating the slurry for said energy device electrodes on the surface of a current collection material, and drying.

According to the binder composition for an energy device electrode of the present invention, the polymer latex (a) has a smaller particle diameter of the dispersed particles than the polymer latex (b), and migration easily occurs. The layer has a high binder content due to the polymer latex (a) on the surface side, and a high binder content due to the polymer latex (b) on the interface side with the current collector.
Moreover, since the polymer latex (a) has a high glass transition temperature of the polymer, the stickiness after drying is small, and the polymer latex (b) has a high binding due to the low glass transition temperature of the polymer. Have sex.
Accordingly, it is possible to form an electrode layer having high adhesion to the current collector and excellent in press workability.

Hereinafter, embodiments of the present invention will be described in detail.
The binder composition for energy device electrodes of the present invention (hereinafter referred to as “binder composition”) comprises a polymer latex (a) and a polymer latex (b).
The polymer latex (a) has a number average particle size of dispersed particles of 60 to 140 nm, preferably 80 to 120 nm, a glass transition temperature of 5 to 50 ° C., preferably 10 to 30 ° C., and a toluene gel content of 70% or more. , Preferably 85% or more.
The polymer latex (b) has a number average particle size of dispersed particles of 150 to 280 nm, preferably 180 to 260 nm, a glass transition temperature of −50 ° C. to 0 ° C., preferably −30 to −5 ° C., and toluene. The gel content is 70% or more, preferably 85% or more.
Here, the “toluene gel content” refers to a value indicating the percentage of the mass of the solid content insoluble in toluene with respect to the mass of the entire solid content in the polymer latex.

In the polymer latex (a), when the particle diameter of the dispersed particles is less than 80 nm, good adhesion between the formed electrode layer and the current collector tends not to be obtained. On the other hand, when the particle diameter of the dispersed particles exceeds 120 nm, the binder due to the polymer latex (a) is less likely to be unevenly distributed on the surface side of the electrode layer to be formed, so that the press workability of the electrode layer is deteriorated. .
In addition, when the glass transition temperature is less than 5 ° C., the surface of the electrode layer to be formed is sticky, and the electrode layer is likely to stick to the surface of the press plate at the time of pressing. Sexuality gets worse. On the other hand, when the glass transition temperature exceeds 50 ° C., there is a tendency that good adhesion between the formed electrode layer and the current collector cannot be obtained.
In addition, when the content of toluene gel is less than 70%, the formed electrode layer is easily dissolved in an electrolyte solution in an energy device such as a lithium ion secondary battery. Tend to influence.

In the polymer latex (b), when the particle size of the dispersed particles is less than 150 nm, the binder due to the polymer latex (b) tends to be unevenly distributed on the surface of the electrode layer due to the influence of migration. Since the glass transition temperature is low, the press workability of the electrode layer is deteriorated. On the other hand, when the particle diameter of the dispersed particles exceeds 280 nm, the surface area of the dispersed particles of the latex is small, so that good adhesion between the formed electrode layer and the current collector tends not to be obtained.
Moreover, it is difficult to synthesize a polymer latex having a glass transition temperature of less than −50 ° C. in consideration of the glass transition temperature of a polymer obtained from a monomer described later. On the other hand, when the glass transition temperature exceeds 0 ° C., good adhesion between the formed electrode layer and the current collector tends not to be obtained.
In addition, when the content of toluene gel is less than 70%, the formed electrode layer is easily dissolved in an electrolyte solution in an energy device such as a lithium ion secondary battery. Tend to influence.

The solid concentration in each of the polymer latex (a) and the polymer latex (b) is preferably 30 to 60% by mass, and more preferably 40 to 50% by mass.
Further, the ratio of the polymer latex (a) to the polymer latex (b) is preferably 1: 1 to 1: 4, more preferably 1: 2 to 1: 3, in terms of the solid mass ratio. is there. When the ratio of the polymer latex (a) is too small, the content of the binder due to the latex (b) is increased on the surface side of the electrode layer to be formed, so that the press workability of the electrode layer is deteriorated. is there. On the other hand, when the ratio of the polymer latex (b) is too small, the binder content of the latex (a) increases on the interface side with the current collector in the electrode layer to be formed. Adhesiveness with an electric body may be significantly reduced.

  Each of polymer latex (a) and polymer latex (b) (hereinafter collectively referred to as “polymer latex”) includes monomer (I) composed of an aromatic vinyl compound, aliphatic conjugated diene. A monomer (II) made of an ethylene-based compound, a monomer (III) made of an ethylenically unsaturated carboxylic acid, and a monomer (IV) made of another vinyl compound copolymerizable therewith It is preferable to consist of the copolymer obtained by emulsion-polymerizing the monomer composition which becomes.

Specific examples of the aromatic vinyl compound constituting the monomer (I) include styrene, sodium styrenesulfonate, α-methylstyrene, p-methylstyrene, vinyltoluene, chlorostyrene, divinylbenzene, and the like. Of these, styrene is preferred. Specific examples of the aliphatic conjugated diene compound constituting the monomer (II) include butadiene, isoprene, 2-chloro-1,3-butadiene, chloroprene and the like. Among these, butadiene is preferable.
Examples of the ethylenically unsaturated carboxylic acid constituting the monomer (III) include acrylic acid, itaconic acid, fumaric acid and maleic acid. Among these, acrylic acid and itaconic acid are preferred.
The compounds constituting the monomer (IV) include acrylonitrile, methyl (meth) acrylate, 2-ethylhexyl acrylate, butyl acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and (meth) acrylic. N-propyl acid, i-propyl (meth) acrylate, decyl (meth) acrylate, hydroxymethyl (meth) acrylate, hydroxyethyl (meth) acrylate, ethylene glycol (meth) acrylate, and the like. Of these, acrylonitrile, methyl (meth) acrylate, and butyl (meth) acrylate are preferred.

In the monomer composition for obtaining the polymer latex (a), in all monomers, the monomer (I) is 20 to 50% by mass, the monomer (II) is 15 to 35% by mass, It is preferable that the monomer (III) is contained in a proportion of 2 to 6% by mass and the monomer (IV) is contained in a proportion of 1 to 20% by mass. In particular, the monomer (IV) is 10% by mass of acrylonitrile. It is preferable that it is contained above.
Further, in the monomer composition for obtaining the polymer latex (b), the monomer (I) is 15 to 35% by mass and the monomer (II) is 30 to 60% by mass in all monomers. %, Monomer (III) is preferably contained in a proportion of 2 to 6% by mass, and monomer (IV) is preferably contained in a proportion of 1 to 20% by mass.

In the polymer latex (a) and the polymer latex (b), in order to obtain a copolymer having a glass transition temperature in the above range, the type and ratio of the monomer used may be adjusted.
For example, styrene is selected as the monomer (I), acrylonitrile, methyl methacrylate, etc. are selected as the monomer (IV), or a high ratio of these monomers is used to obtain a high glass transition temperature. be able to. Further, by selecting 2-ethylhexyl acrylate, butyl acrylate or the like as the monomer (IV), or by using these monomers (IV) or monomers (II) in a high ratio, a low glass A transition temperature can be obtained.

In the polymer latex (a) and the polymer latex (b), in order to obtain dispersed particles having a number average particle diameter in the above range, the amount of emulsifier used may be adjusted during the emulsion polymerization, or the electrolyte may be used. What is necessary is just to add or to adjust the quantity of the monomer which has a functional group.
For example, when the amount of emulsifier used is large, dispersed particles having a small number average particle size can be obtained, and when the amount of emulsifier used is small, dispersed particles having a small number average particle size can be obtained.

  The binder composition of the present invention contains the polymer latex (a) and the polymer latex (b) described above. Such a binder composition is based on the number measured by a laser diffraction method. The particle size distribution of each particle has a peak in the range of 80 to 120 nm and in the range of 150 to 280 nm, and when measured using a differential scanning calorimeter, And each having a glass transition temperature in the range of −50 ° C. to 0 ° C.

According to the above binder composition, the polymer latex (a) has a smaller particle diameter of the dispersed particles and is more likely to migrate as compared to the polymer latex (b). On the side, the content of the binder due to the polymer latex (a) increases, and on the side of the interface with the current collector, the content of the binder due to the polymer latex (b) increases.
Moreover, since the polymer latex (a) has a high glass transition temperature of the polymer, the stickiness after drying is small, and the polymer latex (b) has a high binding due to the low glass transition temperature of the polymer. Have sex.
Therefore, an energy device electrode having an electrode layer having high adhesion to the current collector and excellent in press workability can be obtained.

The slurry for an energy device electrode of the present invention (hereinafter referred to as “electrode slurry”) comprises the above-mentioned electrode binder composition and an electrode active material.
The electrode active material is not particularly limited, but when used for a lithium ion secondary battery electrode, an organic polymer compound such as carbon, for example, phenol resin, polyacrylonitrile, cellulose, etc. is fired for the negative electrode. Can be used, carbon materials obtained by firing coke or pitch, artificial graphite, natural graphite, etc., and when used for electric double layer capacitor electrodes, activated carbon, activated carbon fiber, silica Alumina, etc. can be used, and when used for lithium ion capacitor electrodes, carbon materials such as graphite, non-graphitizable carbon, hard carbon, coke, polyacene organic semiconductor (PAS), etc. should be used. Can do.
Further, in the electrode slurry of the present invention, thickeners, dispersants such as sodium hexametaphosphate, sodium tripolyphosphate, sodium polyacrylate, nonionic or anionic surfactants as latex stabilizers, antifoaming An additive such as an agent may be contained.

  In the slurry for electrodes of the present invention, the solid content in the binder composition is preferably contained in a proportion of 0.1 to 10 parts by mass, more preferably 0.3 to 100 parts by mass of the electrode active material. -4 parts by mass. When the ratio of the solid content of the binder composition is too small, good adhesion tends to be not obtained. On the other hand, when the ratio of the solid content of the binder composition is excessive, the overvoltage tends to increase and affect the battery characteristics.

The electrode slurry of the present invention is prepared by mixing the binder composition, the electrode active material, and additives used as necessary, for example, with a stirrer, a defoamer, a bead mill, a high-pressure homogenizer, or the like. Can do.
In addition, the preparation of the electrode slurry can be performed under reduced pressure, thereby preventing bubbles from being generated in the obtained electrode layer.

In the present invention, the electrode slurry is applied to the surface of the current collector and dried, and the resulting coating film is pressed to form an electrode layer on the surface of the current collector. An energy device electrode is obtained.
As the current collector, a metal foil, an etching metal foil, an expanded metal or the like can be used. As a material constituting the current collector, a metal material such as aluminum, copper, nickel, tantalum, stainless steel, titanium or the like can be used. It can be appropriately selected and used according to the type of the target energy device. Further, the thickness of the current collector is, for example, 5 to 30 μm, preferably 8 to 25 μm when constituting an electrode for a lithium secondary battery. For example, when constituting an electrode for an electric double layer capacitor. 5 to 100 μm, preferably 10 to 70 μm, more preferably 15 to 30 μm.
As a means for applying the electrode slurry, a doctor blade method, a reverse roll method, a comma bar method, a gravure method, an air knife method, or the like can be used.
Moreover, as conditions of the drying process of the coating film of the slurry for electrodes, it is preferable that processing temperature is 20-250 degreeC, for example, and it is still more preferable that it is 50-150 degreeC. Moreover, it is preferable that processing time is 1 to 120 minutes, for example, and it is still more preferable that it is 5 to 60 minutes.
Moreover, as a means to press-work, a high pressure super press, a soft calendar, a 1-ton press machine, etc. can be utilized.
The press working conditions are appropriately set according to the processing machine to be used.
Thus the electrode layer thus formed is, for example, a thickness of 40 to 100 [mu] m, density of 1.3~2.0g / cm ^2.

The energy device electrode of the present invention can be suitably used as an electrode of an energy device such as a lithium ion secondary battery, an electric double layer capacitor, or a lithium ion capacitor.
When a lithium ion secondary battery is constituted by the energy device electrode of the present invention, an electrolytic solution in which an electrolyte made of a lithium compound is dissolved in a solvent is used.
Specific examples of the _{electrolyte, LiClO 4, LiBF 4, LiI} , LiPF 6, LiCF 3 SO 3, LiAsF 6, LiSbF 6, LiAlCl 4, LiCl, LiBr, LiB (C 2 H 5) 4, LiCH 3 SO 3, _{LiC 4 F 9 SO 3, Li} (C 4 F 3 SO 2) 2 N, Li [CO 2) 2] such as ₂ B and the like.
Specific examples of the solvent include carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; lactones such as γ-butyrolactone; trimethoxysilane, 1,2-dimethoxyethane, diethyl Ethers, ethers such as 2-ethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, sulfoxides such as dimethyl sulfoxide, oxolanes such as 1,3-dioxolane, 4-methyl-1,3-dioxolane, acetonitrile, nitromethane, etc. Nitrogen-containing compounds, methyl formate, methyl acetate, butyl acetate, methyl propionate, ethyl propionate, phosphate triesters, diglyme, triglyme, tetragram Grimes such as acetone, ketones such as acetone, diethyl ketone, methyl ethyl ketone, methyl isobutyl ketone, sulfones such as sulfolane, oxazolidinones such as 2-methyl-2-oxazolidinone, 1,3-propane sultone, 4-butane sultone, And sultone such as naphtha sultone.
Further, when an electric double layer capacitor is constituted by the energy device electrode of the present invention, tetraethylammonium tetrafluoroborate, triethylmethylammonium tetrafluoroborate, tetraethylammonium hexafluorophosphate, etc. in the above solvent as an electrolyte A material in which the electrolyte is dissolved is used.
Moreover, when comprising a lithium ion capacitor with the energy device electrode of this invention, the thing similar to the case where said lithium ion secondary battery is comprised can be used as electrolyte solution.

Hereinafter, specific examples of the present invention will be described, but the present invention is not limited thereto.
In the following examples and comparative examples, “parts” and “%” are based on mass unless otherwise specified.
Moreover, the measurement method of various physical properties and the evaluation method of various properties are as follows.

[Binder composition]
(1) Measurement of average particle size:
The particle size was measured using a laser particle size analysis system FPAR1000 manufactured by Otsuka Electronics Co., Ltd.
(2) Measurement of glass transition point (Tg):
An aqueous dispersion adjusted to pH 8 with 0.5 N ammonia water was applied to a glass plate and dried at 120 ° C. for 1 hour to prepare a polymer film. This film was measured using a differential scanning calorimeter manufactured by Seiko Denshi Kogyo Co., Ltd. as a test piece.
(3) Toluene gel content:
An aqueous dispersion (2.0 g) was added to 100 g of methanol to solidify the solid content, and the solid content was collected by filtration through a 300-mesh wire mesh. The obtained solid content was washed with methanol, and then washed with methanol at 60 ° C. Vacuum drying was performed under the conditions of time. The mass of this solid content (W0 (g)) was measured, the solid content was put into 50 ml of toluene, stirred at 50 ° C. for 3 hours, cooled to 25 ° C., and filtered through a 300-mesh wire mesh. 10 ml of the filtrate was collected and dried with a 120 ° C. hot plate until the mass became constant, the mass of the dried product (W1 (g)) was measured, and the toluene gel content was calculated by the following formula.
Toluene gel content (%) = {(W0-5 × W1) / W0} × 100

[Secondary battery electrode]
(1) Peel strength:
A test piece having a width of 2 cm and a length of 12 cm was cut out from the secondary battery electrode (negative electrode), and the surface of the test piece on the electrode layer side was attached to an aluminum plate using a double-sided tape. In addition, a 18 mm wide tape (trade name “Cero Tape (registered trademark)” (manufactured by Nichiban Co., Ltd.)) (specified in JIS Z1522) is attached to the surface of the current collector of the test piece, and the speed is 50 mm / min in the 90 ° direction. The strength (g / 2 cm) when the tape was peeled was measured 6 times, and the average value was calculated as the peel strength (g / 2 cm).
In addition, it can be evaluated that the larger the peel strength value, the higher the adhesion strength between the current collector and the electrode layer, and the more difficult the electrode layer peels from the current collector.
(2) Press workability:
A test piece having a width of 2 cm and a length of 12 cm was cut out from the secondary battery electrode (negative electrode), this test piece was pressed with a 5 t press, and the presence or absence of peeling of the electrode layer in the test piece was examined. The case where there was peeling was set as x.
(3) Binder component distribution:
Samples of 2 mg were collected from the surface side of the electrode layer and the interface side with the current collector, respectively, and the composition of latex present in the electrode was analyzed using an HP pyrolysis gas chromatograph manufactured by Hewlett-Packard Co. The polymer latex according to the binder component is shown. Here, when the sample is taken from the current collector and interface side in the electrode layer, the electrode layer is peeled off from the current collector by the same method as the measurement of peel strength described above, and the interface with the current collector is removed. Exposed.

<Preparation of polymer latex>
Preparation Example 1:
In a temperature-controllable autoclave equipped with a stirrer, 200 parts of water, 0.3 part of sodium dodecylbenzenesulfonate, 1.0 part of potassium persulfate, 0.5 part of sodium bisulfite, α-methylstyrene dimer 2 parts and 0.1 part of dodecyl mercaptan were charged together and heated to 45 ° C., then the monomer components shown in Table 1 below were added over 4 hours, and then reacted at 45 ° C. for 6 hours. It was confirmed that the polymerization conversion was 70% or more. Furthermore, the polymer latex was obtained by making it react at 70 degreeC for 6 hours. Let the obtained polymer latex be latex (a1). The properties of the latex (a1) are shown in Table 1 below.

Preparation Example 2:
A polymer latex was prepared in the same manner as in Preparation Example 1 except that the amount of sodium dodecylbenzenesulfonate was changed from 0.3 part to 0.5 part and the monomer component shown in Table 1 was used. Obtained. Let the obtained polymer latex be latex (a2). The properties of the latex (a2) are shown in Table 1 below.

Preparation Example 3:
A polymer latex was obtained in the same manner as in Preparation Example 1, except that the monomer components shown in Table 1 below were used. Let the obtained polymer latex be latex (c1). The properties of the latex (c1) are shown in Table 1 below.

Preparation Example 4:
A polymer latex was prepared in the same manner as in Preparation Example 1 except that the amount of sodium dodecylbenzenesulfonate was changed from 0.3 part to 0.1 part and the monomer component shown in Table 1 was used. Obtained. Let the obtained polymer latex be latex (b1). The properties of the latex (b1) are shown in Table 1 below.

Preparation Example 5:
A polymer latex was prepared in the same manner as in Preparation Example 1, except that the amount of sodium dodecylbenzenesulfonate was changed from 0.3 part to 0.2 part and the monomer component shown in Table 1 was used. Obtained. Let the obtained polymer latex be latex (b2). The properties of the latex (b2) are shown in Table 1 below.

Preparation Example 6:
A polymer latex was obtained in the same manner as in Preparation Example 1, except that the amount of sodium dodecylbenzenesulfonate was changed from 0.3 part to 0.1 part. Let the obtained polymer latex be latex (c2). The properties of the latex (c2) are shown in Table 1 below.

<Example 1>
The latex (a1) is 0.5 parts in terms of solids, the latex (b1) is 0.5 parts in terms of solids, and 1 part of “CMC1290” manufactured by Daicel Chemical Co., Ltd. A slurry for an electrode was prepared by stirring and mixing 100 parts of the substance using a stirring defoamer at 200 rpm for 2 minutes, 1800 rpm for 5 minutes, and under vacuum at 1800 rpm for 1.5 minutes.
Next, the prepared electrode slurry is uniformly applied to the surface of the current collector made of copper foil by a doctor blade method so that the film thickness after drying is 150 μm, and is dried at 120 ° C. for 20 minutes, and thereafter A secondary battery electrode was obtained by pressing with a roll press so that the density of the obtained electrode layer was 1.8 g / cm ³ .

<Example 2>
A slurry for an electrode was prepared in the same manner as in Example 1 except that latex (a2) was used instead of latex (a1) and latex (b2) was used instead of latex (b1). Obtained.

<Example 3>
A slurry for an electrode was prepared in the same manner as in Example 1 except that latex (b2) was used instead of latex (b1) to obtain a secondary electrode.

<Example 4>
A slurry for an electrode was prepared in the same manner as in Example 1 except that the latex (a2) was used instead of the latex (a1) to obtain a secondary electrode.

<Comparative example 1>
The slurry for the electrode was prepared in the same manner as in Example 1 except that the latex (a1) was changed from 0.5 part to 1 part in terms of solid content and the latex (b1) was not used. Obtained.

<Comparative example 2>
The slurry for the electrode was prepared in the same manner as in Example 1 except that the latex (b1) was changed from 0.5 part to 1 part in terms of solid content and the latex (a1) was not used. Obtained.

<Comparative Example 3>
A slurry for an electrode was prepared in the same manner as in Example 1 except that latex (c1) was used instead of latex (a1) and latex (c2) was used instead of latex (b1). Obtained.

  The peel strength, press workability, and binder component distribution of the secondary battery electrodes obtained in Examples 1 to 4 and Comparative Examples 1 to 3 are shown in Table 2 below.

  As is clear from the results of Table 2, according to Examples 1 to 4, it was confirmed that a secondary battery electrode having an electrode layer having high adhesion to the current collector and excellent in press workability was obtained. It was done.

Claims (8)

It contains a polymer latex having a toluene gel content of 70% or more,
The polymer latex has a number-based particle size distribution measured by a laser diffraction method having a peak in each of 80 to 120 nm and 150 to 280 nm, and a differential scanning calorimeter. A binder for an energy device electrode, having a peak indicating a glass transition temperature in each of a range of 5 to 50 ° C. and a range of −50 ° C. to 0 ° C. Composition. A polymer latex (a) having a number average particle size of 80 to 120 nm, a glass transition temperature of 5 to 50 ° C., and a toluene gel content of 70% or more;
An energy device electrode comprising a polymer latex (b) having a number average particle size of 150 to 280 nm, a glass transition temperature of -50 ° C to 0 ° C, and a toluene gel content of 70% or more. Binder composition.   Each of the polymer latex (a) and the polymer latex (b) includes a monomer (I) made of an aromatic vinyl compound, a monomer (II) made of an aliphatic conjugated diene compound, an ethylenically unsaturated carboxylic acid. 3. A copolymer obtained by emulsion polymerization of a monomer (III) comprising an acid and a monomer (IV) comprising another vinyl compound copolymerizable therewith. The binder composition for energy device electrodes described in 1. The binder for an energy device electrode according to claim 3, wherein the monomer (I) for obtaining the polymer latex (a) contains (meth) acrylonitrile in an amount of 10% by mass or more based on the total monomers. Composition. A binder composition for an energy device electrode according to any one of claims 1 to 4,
An energy device electrode slurry comprising an electrode active material.   The solid content in the binder composition for an energy device electrode is contained at a ratio of 0.1 to 10 parts by mass with respect to 100 parts by mass of the electrode active material, for the energy device electrode according to claim 5. slurry. Current collector,
An energy device electrode comprising an electrode layer formed by applying and drying the slurry for an energy device electrode according to claim 6 on the surface of the current collector.   A method for producing an energy device electrode, comprising: applying a slurry for an energy device electrode according to claim 6 on a surface of a current collector, and drying the slurry.