JPWO2019004216A1 - Binder composition for electrochemical device electrode, slurry composition for electrochemical device electrode, electrode for electrochemical device, electrochemical device, and method for producing electrode for electrochemical device - Google Patents

Abstract

It is an object of the present invention to provide a binder composition for an electrochemical device electrode, which allows the electrode mixture layer to be easily densified and firmly adhered to the current collector. The binder composition of the present invention is a binder composition for electrochemical device electrodes containing a polymer, wherein the polymer is a nitrile group-containing monomer unit and at least two aliphatic conjugated diene monomers. Including units and.

Description

  The present invention relates to a binder composition for an electrochemical device electrode, a slurry composition for an electrochemical device electrode, an electrode for an electrochemical device, an electrochemical device, and a method for producing an electrode for an electrochemical device.

  BACKGROUND ART Electrochemical devices such as lithium-ion secondary batteries and electric double layer capacitors are small and lightweight, have high energy density, and can be repeatedly charged and discharged, and are used in a wide range of applications.

  Here, for example, an electrode for a lithium ion secondary battery usually includes a current collector and an electrode mixture layer (a positive electrode mixture layer or a negative electrode mixture layer) formed on the current collector. Then, the electrode mixture layer is formed, for example, by applying a slurry composition containing an electrode active material and a binder composition containing a binder on a current collector, and drying the applied slurry composition. It is formed.

Therefore, in recent years, attempts have been made to improve the binder composition used for forming the electrode mixture layer in order to further improve the performance of the electrochemical device (see, for example, Patent Documents 1 and 2).
In Patent Document 1, by using a hydrogenated carboxy-modified rubber as a binder to manufacture a negative electrode for a lithium-ion secondary battery, the negative electrode peel strength is increased, and high-rate discharge characteristics of the lithium-ion secondary battery and Improves cycle characteristics.
In Patent Document 2, a carboxy-modified rubber is used as a binder, and a base is used as a dispersant to produce a battery electrode plate, thereby enhancing the peel strength of the battery electrode plate and improving the cycle characteristics of the battery. Is improving.

JP-A-11-111268 JP, 2013-89528, A

Here, in recent years, electrochemical devices have been required to have a higher capacity. In order to increase the capacity of the electrochemical device, it is effective to use an electrode in which the electrode mixture layer on the current collector has a high density and a high film thickness. However, when forming the electrode mixture layer using the above conventional binder composition, it is difficult to achieve sufficient densification even if press treatment is performed to achieve high density of the electrode mixture layer. Met.
Further, when forming the electrode mixture layer using the above-mentioned conventional binder composition, when the electrode mixture layer is made thicker, the components such as the electrode active material contained in the electrode mixture layer are separated from the electrode mixture layer. There was also a problem that it became easy to detach. When an electrode including such an electrode mixture layer is used, the cycle characteristics of the electrochemical device may be impaired.
That is, the above-mentioned conventional binder composition has room for improvement in that the electrode mixture layer can be easily densified and the electrode mixture layer can be firmly adhered to the current collector.

Therefore, the present invention provides a binder composition for an electrochemical element electrode and a slurry composition for an electrochemical element electrode, which can firmly adhere the electrode mixture layer to a current collector while easily densifying the electrode mixture layer. The purpose is to provide.
Another object of the present invention is to provide an electrode for an electrochemical device and a method for producing the electrode for an electrochemical device, which can increase the capacity of the electrochemical device and can exhibit excellent cycle characteristics in the electrochemical device. And
Another object of the present invention is to provide an electrochemical device having a high capacity and excellent cycle characteristics.

  The present inventor has conducted earnest studies for the purpose of solving the above problems. Then, the inventor of the present invention, if a binder composition containing a nitrile group-containing monomer and a polymer obtained by polymerizing at least two kinds of aliphatic conjugated diene monomers is used as a binder, The present invention has been completed by finding that it is possible to form an electrode mixture layer that has a high density and can firmly adhere to a current collector.

That is, the present invention is intended to advantageously solve the above problems, and the binder composition for electrochemical device electrodes of the present invention is a binder composition for electrochemical device electrodes containing a polymer. The polymer is characterized by containing a nitrile group-containing monomer unit and at least two kinds of aliphatic conjugated diene monomer units. By using the binder composition containing the polymer having the above-described composition, the electrode mixture layer can be easily densified and firmly adhered to the current collector. Then, by using the electrode provided with the electrode mixture layer obtained by using the binder composition containing the polymer having the above-mentioned composition, it is possible to increase the capacity of the electrochemical device, and excellent cycle characteristics for the electrochemical device. Can be demonstrated.
In the present invention, “including a monomer unit” means “a repeating unit derived from a monomer is included in a polymer obtained by using the monomer”.

  Here, in the binder composition for an electrochemical device electrode of the present invention, the aliphatic conjugated diene monomer unit preferably contains an aliphatic conjugated diene monomer unit having 5 to 12 carbon atoms. When the polymer contains, as the aliphatic conjugated diene monomer unit, a repeating unit derived from the aliphatic conjugated diene monomer having 5 to 12 carbon atoms, the electrode composite material layer can be easily densified and the current can be collected. Strong adhesion to the body can be achieved at a higher level.

Further, in the binder composition for electrochemical device electrodes of the present invention, the ratio of the aliphatic conjugated diene monomer unit having 5 to 12 carbon atoms in the polymer is 1% by mass to 50% by mass. Preferably there is. When the polymer contains the aliphatic conjugated diene monomer unit having 5 to 12 carbon atoms in the above-mentioned ratio, the electrode mixture layer can be easily densified and firmly adhered to the current collector. Can be achieved at a high level.
In the present invention, in a polymer produced by copolymerizing a plurality of types of monomers, the “ratio of monomer units” formed by polymerizing a certain monomer is usually its weight. This is the same as the ratio (charge ratio) of the certain monomer to all the monomers used for the polymerization of the combined product. Further, in the present invention, the “ratio of monomer units” in the polymer can be measured by using a nuclear magnetic resonance (NMR) method such as ¹ H-NMR and ¹³ C-NMR.

  And in the binder composition for electrochemical device electrodes of the present invention, it is preferable that the aliphatic conjugated diene monomer unit includes a 1,3-butadiene unit. When the polymer includes a repeating unit derived from 1,3-butadiene as the aliphatic conjugated diene monomer unit, the electrode composite material layer can be more easily densified.

  Furthermore, in the binder composition for an electrochemical device electrode of the present invention, the proportion of the 1,3-butadiene unit in the polymer is preferably 1% by mass or more and 50% by mass or less. When the polymer contains 1,3-butadiene units in the above-mentioned proportion, it is possible to easily attain high density of the electrode mixture layer and firm adhesion to the current collector at a higher level.

  Here, in the binder composition for an electrochemical device electrode of the present invention, the ratio of the nitrile group-containing monomer unit in the polymer is preferably 20% by mass or more and 85% by mass or less. When the polymer contains the nitrile group-containing monomer unit in the above-mentioned ratio, the electrode mixture layer can be easily densified and firmly adhered to the current collector at a higher level. In addition, the affinity of the polymer for an organic solvent (particularly, a polar organic solvent such as N-methylpyrrolidone) is secured, and a binder composition in which the polymer is well dissolved in the organic solvent can be obtained.

  In the binder composition for electrochemical device electrodes of the present invention, the aliphatic conjugated diene monomer unit comprises an aliphatic conjugated diene monomer unit having 5 to 12 carbon atoms and a 1,3-butadiene unit. The ratio of the ratio of the aliphatic conjugated diene monomer unit having 5 to 12 carbon atoms to the ratio of the 1,3-butadiene unit in the polymer is 0.02 to 50. preferable. The polymer contains both an aliphatic conjugated diene monomer unit having 5 or more and 12 or less carbon atoms and a 1,3-butadiene unit, and has 5 or more carbon atoms based on the ratio of 1,3-butadiene units in the polymer. When the ratio of the ratio of the aliphatic conjugated diene monomer units of 12 or less is within the above range, easy densification of the electrode mixture layer and firm adhesion to the current collector are achieved at a higher level. can do.

  Moreover, this invention aims at solving the said subject advantageously, and the slurry composition for electrochemical device electrodes of this invention is an electrode active material, and the binder composition for electrochemical device electrodes mentioned above. And any of the above are included. Thus, if the electrode mixture layer is formed using the slurry composition containing any of the binder compositions described above, the electrode mixture layer is easily densified and firmly adhered to the current collector. be able to. When an electrode including an electrode mixture layer obtained by using the above-mentioned slurry composition is used, it is possible to increase the capacity of the electrochemical device and to exhibit excellent cycle characteristics in the electrochemical device.

  Here, in the slurry composition for electrochemical device electrodes of the present invention, the electrode active material is preferably an electrode active material containing nickel. If the electrode active material containing nickel is used, the capacity of the electrochemical device can be further increased.

  Moreover, this invention aims at solving the said subject advantageously, The electrode for electrochemical devices of this invention was formed using any of the slurry compositions for electrochemical device electrodes mentioned above. It is characterized by comprising an electrode mixture layer. As described above, by using any of the above-mentioned slurry compositions, it is possible to produce an electrode which can increase the capacity of an electrochemical device and can exhibit excellent cycle characteristics in the electrochemical device.

  Moreover, this invention aims at solving the said subject advantageously, and the electrochemical device of this invention is equipped with the electrode for electrochemical devices mentioned above, It is characterized by the above-mentioned. Thus, by using the above-mentioned electrode for electrochemical device, an electrochemical device having high capacity and excellent cycle characteristics can be obtained.

And this invention aims at solving the said subject advantageously, The manufacturing method of the electrode for electrochemical devices of this invention collects any of the said slurry compositions for electrochemical devices electrodes. A step of applying on a current collector, a step of drying the electrochemical device electrode slurry composition applied on the current collector, to form a pre-press electrode mixture layer on the current collector, Roll-pressing the electrode mixture layer before pressing at a linear pressure of 500 kN / cm or more and 3000 kN / cm or less to obtain an electrode mixture layer after pressing. By adopting the above-mentioned procedure using any of the above-mentioned slurry compositions, the electrode mixture layer can be sufficiently densified and firmly adhered to the current collector.
In the present invention, the "line pressure" is a value obtained by dividing the load (kN) applied to the pre-pressing electrode mixture layer during roll pressing by the width (cm) of the pre-pressing electrode mixture layer. Is.

ADVANTAGE OF THE INVENTION According to this invention, the binder composition for electrochemical device electrodes and the slurry composition for electrochemical device electrodes which can make the said electrode composite material layer stick firmly to a collector, densifying an electrode composite material layer easily. Can be provided.
Further, according to the present invention, it is possible to provide an electrochemical device electrode having a high capacity and capable of exhibiting excellent cycle characteristics in the electrochemical device, and a method for producing the electrochemical device electrode. You can
Furthermore, according to the present invention, it is possible to provide an electrochemical device having a high capacity and excellent cycle characteristics.

Hereinafter, embodiments of the present invention will be described in detail.
Here, the binder composition for electrochemical device electrodes of the present invention can be used when preparing the slurry composition for electrochemical device electrodes of the present invention. Then, the slurry composition for electrochemical device electrodes of the present invention prepared by using the binder composition for electrochemical device electrodes of the present invention, for example, using the method for producing an electrode for electrochemical device of the present invention, It can be used when producing the electrode for electrochemical device of the invention. Further, the electrochemical device of the present invention is characterized by using the electrode for electrochemical device of the present invention produced by using the slurry composition for electrochemical device electrode of the present invention.

(Binder composition for electrochemical device electrode)
The binder composition of the present invention contains a polymer, and optionally further contains other components that can be incorporated in the electrode of the electrochemical device. Moreover, the binder composition of the present invention may further contain a solvent. Here, the polymer contained in the binder composition of the present invention includes a nitrile group-containing monomer unit and at least two kinds of aliphatic conjugated diene monomer units.
And since the binder composition of the present invention contains the above-mentioned polymer as the binder, if the electrode composition layer of the electrode for electrochemical device is formed using the binder composition, the electrode mixture material is formed. The layer can be easily densified and firmly adhered to the current collector.
The reason why the electrode composition layer can be easily densified and firmly adhered to the current collector by using the binder composition of the present invention is not clear, but is as follows. Inferred.
That is, the polymer contained in the binder composition of the present invention contains an aliphatic conjugated diene monomer unit that can contribute to improving the flexibility of the polymer by lowering the glass transition temperature. Then, by forming the aliphatic conjugated diene monomer unit not by one kind alone but by using two or more kinds of aliphatic conjugated diene monomers, the polymer is a blending component such as an electrode active material or a conductive material. The affinity with (particularly, the carbon-based material) is increased, and the compounding components thereof can be satisfactorily dispersed in the slurry composition prepared using the binder composition. Thus, by coating the current collector with the slurry composition in which the components are well dispersed, a high coating density can be realized. Furthermore, according to the slurry composition containing the polymer which is excellent in flexibility and can well disperse the blended components, each component does not become unevenly distributed in forming the electrode mixture layer, and, for example, a relatively low line Even when roll-pressing with pressure, the electrode mixture layer can be well adhered to the current collector while sufficiently increasing the density of the obtained electrode mixture layer. In addition, since the polymer contained in the binder composition of the present invention contains not only the above-mentioned aliphatic conjugated diene monomer unit but also the nitrile group-containing monomer unit, it has excellent strength. Since the polymer having such excellent strength exhibits high binding property, the electrode composition layer can be firmly adhered to the current collector by using the binder composition containing the polymer.

<Polymer>
Polymer is an electrode produced by forming an electrode mixture layer using a slurry composition prepared using a binder composition, the components contained in the electrode mixture layer does not desorb from the electrode mixture layer Hold (ie, function as a binder).

<< Polymer Composition >>
The polymer contains a nitrile group-containing monomer unit and at least two kinds of aliphatic conjugated diene monomer units. That is, the polymer contains a repeating unit derived from at least one nitrile group-containing monomer and a repeating unit derived from at least two aliphatic conjugated diene monomers.
The polymer A may optionally contain a repeating unit (other repeating unit) other than the nitrile group-containing monomer unit and the aliphatic conjugated diene monomer unit.

[Nitrile group-containing monomer unit]
Examples of the nitrile group-containing monomer capable of forming the nitrile group-containing monomer unit include α, β-ethylenically unsaturated nitrile monomers. Specifically, the α, β-ethylenically unsaturated nitrile monomer is not particularly limited as long as it is an α, β-ethylenically unsaturated compound having a nitrile group, for example, acrylonitrile; α-chloroacrylonitrile, Examples include α-halogenoacrylonitrile such as α-bromoacrylonitrile; α-alkylacrylonitrile such as methacrylonitrile and α-ethylacrylonitrile. Among these, acrylonitrile and methacrylonitrile are preferable as the nitrile group-containing monomer from the viewpoint of improving the output characteristics of the electrochemical device while further firmly adhering the electrode mixture layer to the current collector.
The nitrile group-containing monomer may be used alone or in combination of two or more kinds.

  And the ratio of the nitrile group-containing monomer unit contained in the polymer is preferably 20% by mass or more, and 40% by mass or more, when the total repeating units of the polymer are 100% by mass. More preferably, it is more preferably 50% by mass or more, particularly preferably 60% by mass or more, preferably 85% by mass or less, more preferably 80% by mass or less, and 75% by mass or less. Is more preferable. When the proportion of the nitrile group-containing monomer unit in the polymer is 20% by mass or more, the electrode mixture layer can be more firmly adhered to the current collector to further improve the cycle characteristics of the electrochemical device. it can. In addition, the affinity of the polymer for an organic solvent (particularly, a polar organic solvent such as N-methylpyrrolidone) is secured, and a binder composition in which the polymer is well dissolved in the organic solvent can be obtained. On the other hand, when the proportion of the nitrile group-containing monomer unit in the polymer is 85% by mass or less, the glass transition temperature is not excessively increased and the flexibility of the polymer can be secured. Therefore, the electrode mixture layer having a sufficiently high density can be easily formed.

[Aliphatic conjugated diene monomer unit]
The aliphatic conjugated diene monomer unit is formed by two or more kinds of aliphatic conjugated diene monomers. The aliphatic conjugated diene monomer capable of forming the aliphatic conjugated diene monomer unit is not particularly limited, but for example, an aliphatic conjugated diene monomer having 5 to 12 carbon atoms (C5 to 12) Aliphatic conjugated diene monomer) and 1,3-butadiene.

Examples of the aliphatic conjugated diene monomer having 5 to 12 carbon atoms include 2-methyl-1,3-butadiene (isoprene, carbon atom number: 5), 2,3-dimethyl-1,3-butadiene (carbon The number of atoms is 6) and the like. Among these, isoprene is preferable. When the polymer includes an aliphatic conjugated diene monomer unit having 5 to 12 carbon atoms, which is derived from an aliphatic conjugated diene monomer having 5 to 12 carbon atoms, the flexibility of the polymer is secured. It Moreover, it is presumed that the presence of the hydrophobic group (such as a methyl group) existing on the carbon atom having a double bond improves the affinity for the compounding component (particularly, the carbon material) of the polymer. The compounding ingredients can be dispersed more satisfactorily. A higher coating density can be realized by coating the current collector with the slurry composition in which the blended components are better dispersed. In addition, when forming the electrode mixture layer using the slurry composition containing the binder composition, each component is not unevenly distributed, for example, even when roll-pressed at a relatively low linear pressure, While further increasing the density of the electrode mixture layer to be obtained, the electrode mixture layer can be more closely attached to the current collector. Therefore, the high density of the electrode mixture layer and the firm adhesion to the current collector can be achieved at a higher level.
In addition, the aliphatic conjugated diene monomer having 5 to 12 carbon atoms can be used alone or in combination of two or more kinds.

  The ratio of the aliphatic conjugated diene monomer unit having 5 to 12 carbon atoms contained in the polymer is preferably 1% by mass or more, more preferably 5% by mass or more, and 15% by mass. % Or more, more preferably 50% by mass or less, and further preferably 25% by mass or less. When the proportion of the aliphatic conjugated diene monomer unit having 5 to 12 carbon atoms in the polymer is 1% by mass or more, the flexibility of the polymer is improved and the blending component (particularly, carbon material) The compatibility with and improves the coating density. Therefore, it is possible to easily achieve high density of the electrode mixture layer and firm adhesion to the current collector at a higher level. On the other hand, when the proportion of the aliphatic conjugated diene monomer unit having 5 to 12 carbon atoms in the polymer is 50% by mass or less, the glass transition temperature is significantly lowered, and the polymer is excessively softened. Is suppressed, the electrode mixture layer can be satisfactorily adhered to the current collector.

  Further, when the polymer contains 1,3-butadiene units derived from 1,3-butadiene, the glass transition temperature is lowered, so that the flexibility of the polymer is sufficiently ensured and the density of the electrode mixture is increased. The material layer can be formed more easily.

  The ratio of 1,3-butadiene units contained in the polymer is preferably 1% by mass or more, more preferably 5% by mass or more, further preferably 7% by mass or more, 50 It is preferably not more than 25% by mass, more preferably not more than 25% by mass, further preferably not more than 15% by mass. When the proportion of 1,3-butadiene units in the polymer is 1% by mass or more, a sufficiently densified electrode mixture layer can be easily formed. On the other hand, when the proportion of 1,3-butadiene units in the polymer is 50% by mass or less, excessive softening of the polymer due to a large decrease in glass transition temperature is suppressed, so that the electrode mixture layer Can be closely adhered to the current collector.

  Here, from the viewpoint of achieving an even higher density of the electrode mixture layer and firm adhesion to the current collector at an even higher level, the aliphatic conjugated diene monomer has 5 to 12 carbon atoms. It is preferable to use the aliphatic conjugated diene monomer and 1,3-butadiene in combination, and it is more preferable to use isoprene and 1,3-butadiene in combination. That is, the polymer preferably contains both an aliphatic conjugated diene monomer unit having 5 to 12 carbon atoms and a 1,3-butadiene unit, and contains both an isoprene unit and a 1,3-butadiene unit. Is more preferable.

  Further, the ratio of the aliphatic conjugated diene monomer units contained in the polymer (the total of the ratios of at least two kinds of aliphatic conjugated diene monomer units) is 100% by mass of all the repeating units of the polymer. , Preferably 15% by mass or more, more preferably 20% by mass or more, further preferably 25% by mass or more, preferably 80% by mass or less, and 60% by mass or less. Is more preferable, and 50% by mass or less is further preferable. When the proportion of the aliphatic conjugated diene monomer unit in the polymer is 15% by mass or more, the glass transition temperature is not excessively increased and the flexibility of the polymer can be secured. Therefore, the electrode mixture layer having a sufficiently high density can be easily formed. On the other hand, when the proportion of the aliphatic conjugated diene monomer unit in the polymer is 80% by mass or less, the electrode mixture layer is more firmly adhered to the current collector to further improve the cycle characteristics of the electrochemical device. Can be made.

  The proportion of the amount of the aliphatic conjugated diene monomer unit in the total amount of the nitrile group-containing monomer unit and the aliphatic conjugated diene monomer unit contained in the polymer is 15% by mass or more. Is more preferable, 20% by mass or more is more preferable, 80% by mass or less is preferable, 60% by mass or less is more preferable, and 40% by mass or less is further preferable. If the proportion of the aliphatic conjugated diene monomer unit in the total of the nitrile group-containing monomer unit and the aliphatic conjugated diene monomer unit is 15% by mass or more, a sufficiently densified electrode mixture layer is obtained. It can be easily formed, and when it is 80% by mass or less, excessive softening of the polymer due to a large decrease in glass transition temperature is suppressed, so that the electrode mixture layer is favorably used as a current collector. Can be closely attached. Further, when the ratio of the aliphatic conjugated diene monomer unit in the total of the nitrile group-containing monomer unit and the aliphatic conjugated diene monomer unit is 15% by mass or more and 80% by mass or less, the polymer electrolyte solution The degree of swelling in the electrolyte (the degree of swelling in the electrolytic solution) is well controlled, and the polymer exhibits good binding properties in the electrolytic solution. Therefore, the cycle characteristics of the electrochemical device can be further improved.

  In addition, the ratio of the ratio of the aliphatic conjugated diene monomer unit having 5 to 12 carbon atoms to the ratio of 1,3-butadiene unit in the polymer is preferably 0.02 or more, It is more preferably 5 or more, further preferably 1 or more, particularly preferably more than 1, particularly preferably 50 or less, more preferably 10 or less, and preferably 5 or less. More preferably, it is particularly preferably 4 or less. When the ratio of the ratio of the aliphatic conjugated diene monomer unit having 5 or more and 12 or less carbon atoms to the ratio of the 1,3-butadiene unit is 0.02 or more, the flexibility of the polymer is improved and the blending component (In particular, the affinity with the carbon material) is improved, and the coating density is increased. Therefore, it is possible to easily achieve high density of the electrode mixture layer and firm adhesion to the current collector at a higher level. On the other hand, when the ratio of the ratio of the amount of the aliphatic conjugated diene monomer unit having 5 to 12 carbon atoms to the ratio of the 1,3-butadiene unit is 50 or less, the glass transition temperature is significantly lowered. Since excessive softening of the polymer is suppressed, the electrode mixture layer can be well adhered to the current collector.

[Other repeating units]
Other repeating units that the polymer may optionally contain are not particularly limited. For example, the polymer may contain, as a repeating unit, an alkylene structural unit obtained by hydrogenating the above aliphatic conjugated diene monomer unit. The other repeating units contained in the polymer are 0% by mass or more and 10% by mass or less from the viewpoint of easily achieving high density of the electrode mixture layer and strong adhesion to the current collector. It is preferable that the amount is 0% by mass or more and 5% by mass or less, further preferably 0% by mass or more and 2% by mass or less.

<< Preparation of Polymer >>
The polymer can be produced, for example, by polymerizing a monomer composition containing the above-mentioned monomer in an aqueous solvent. Here, in the present invention, the content ratio of each monomer in the monomer composition can be determined according to the content ratio of the monomer unit (repeating unit) in the polymer.
The aqueous solvent is not particularly limited as long as it can disperse the polymer, and water may be used alone, or a mixed solvent of water and another solvent may be used.
The polymerization mode is not particularly limited, and any mode such as solution polymerization method, suspension polymerization method, bulk polymerization method and emulsion polymerization method can be used. As the polymerization method, any method such as ionic polymerization, radical polymerization, living radical polymerization can be used.
The emulsifiers, dispersants, polymerization initiators, polymerization aids, etc. used in the polymerization can be those generally used, and the amount thereof is also the amount generally used.
The electrolytic solution swelling degree of the polymer prepared as described above is usually 100% or more, preferably 110% or more, preferably 500% or less, and 300% or less. Is more preferable. When the degree of swelling of the polymer in the electrolytic solution is 110% or more, the affinity of the polymer for not only the electrolytic solution but also the organic solvent is secured, and a binder composition in which the polymer is well dissolved in the organic solvent can be obtained. . On the other hand, when the degree of swelling of the polymer in the electrolytic solution is 500% or less, the polymer can easily retain the binding property in the electrolytic solution and can exhibit excellent characteristics (particularly cycle characteristics) in the electrochemical device. it can.
Here, in the present invention, the “electrolyte swelling degree” can be measured using the method described in Examples of the present specification.

<Solvent>
The solvent that can be contained in the binder composition is not particularly limited, but an organic solvent is preferable. Examples of the organic solvent include alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol and amyl alcohol; acetone, Ketones such as methyl ethyl ketone and cyclohexanone; esters such as ethyl acetate and butyl acetate; ethers such as diethyl ether, dioxane and tetrahydrofuran; N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone (NMP) Amide polar organic solvents such as; N, N-dimethyl sulfoxide; Aromatic hydrocarbons such as toluene, xylene, chlorobenzene, orthodichlorobenzene, and paradichlorobenzene ; And the like. These may be used alone or in combination of two or more. Among them, NMP is preferable as the solvent.

<Other ingredients>
In the binder composition, in addition to the above components, a binder other than the predetermined polymer, a conductive material, a reinforcing material, a leveling agent, a viscosity modifier, an electrolyte solution additive, and the like are contained in the binder composition. May be. These are not particularly limited, and known ones such as those described in International Publication No. 2012/115096 can be used. Moreover, these components may be used individually by 1 type, and may be used in combination of 2 or more types in arbitrary ratios.

<Preparation of binder composition>
The binder composition of the present invention can be prepared by mixing the above components by a known method. In addition, for example, when the polymer is prepared in the state of an aqueous dispersion, by substituting the aqueous solvent with an organic solvent by a known method, and by adding other components as necessary, include an organic solvent as a solvent. A binder composition can be prepared.

(Slurry composition for electrochemical device electrode)
The slurry composition for electrochemical device electrodes of the present invention is a slurry-like composition containing at least an electrode active material and the above-described binder composition for electrochemical device electrodes of the present invention. In other words, the slurry composition of the present invention is usually formed by dissolving and / or dispersing the electrode active material, the above-mentioned polymer, and the above-mentioned other components optionally blended in the above-mentioned solvent. It is a composition. Since the slurry composition of the present invention contains the binder composition of the present invention described above, if the electrode composite material layer is formed using the slurry composition of the present invention, the electrode composite material layer can be easily increased. It is possible to firmly adhere to the current collector while increasing the density.

<Electrode active material>
The electrode active material is a material that exchanges electrons in the electrode of the electrochemical device. The slurry composition of the present invention preferably contains an electrode active material containing nickel (hereinafter, may be abbreviated as “Ni-containing electrode active material”) as the electrode active material. If the electrode containing the Ni-containing electrode active material is used, the capacity of the electrochemical device can be further increased. The Ni-containing electrode active material can be particularly preferably used as a positive electrode active material in a non-aqueous secondary battery such as a lithium ion secondary battery.

<< Ni-containing electrode active material >>
The Ni-containing electrode active material, for example, the formula _{(A): Li (Ni x} Co y M (1-x-y)) in _{O 2} [formula (A), M is manganese (Mn), magnesium (Mg ), Zirconium (Zr), molybdenum (Mo), tungsten (W), aluminum (Al), chromium (Cr), vanadium (V), cerium (Ce), titanium (Ti), iron (Fe), potassium (K). ), Gallium (Ga), and indium (In), and x and y satisfy the relational expressions of 0 <x ≦ 1, 0 ≦ y <1, and x + y ≦ 1. ] The lithium containing composite oxide represented by these can be used.

Among them but corresponding to the above formula (A), from the viewpoint of enhancing the capacity of the electrochemical device further, formula _{(A1): Li (Ni x} Co y Al (1-x-y)) O 2 [ wherein (A1 ), X and y satisfy the relational expressions of 0.30 ≦ x ≦ 1, 0 ≦ y <0.7, and x + y ≦ 1. ] The lithium-containing composite oxide represented by Further, the inter alia although corresponding (A), the From the viewpoint of the capacity and safety of the electrochemical device with good balance is improved, the formula _{(A2): Li (Ni x} Co y Mn (1-x-y)) O ₂ [In the formula (A2), x and y satisfy the relational expressions of 0.30 ≦ x ≦ 1, 0 ≦ y <0.7, and x + y ≦ 1. ] The lithium-containing composite oxide represented by

<< Other electrode active materials >>
As the electrode active material, an electrode active material other than the above Ni-containing electrode active material can be used. The case where the electrochemical device electrode slurry composition is a lithium ion secondary battery electrode slurry composition will be described below as an example, but the present invention is not limited to the following example.

As a positive electrode active material for a lithium ion secondary battery, in addition to the Ni-containing electrode active material described above, lithium-containing cobalt oxide (LiCoO ₂ ), lithium manganate (LiMn ₂ O ₄ ), olivine-type lithium iron phosphate ( Known positive electrode active materials such as LiFePO ₄ ), olivine-type lithium manganese phosphate (LiMnPO ₄ ), and a lithium-excess spinel compound represented by Li _{1 + x} Mn _2-x O ₄ (0 <x <2) are included.
The amount and particle size of the positive electrode active material blended are not particularly limited and may be the same as those of conventionally used positive electrode active materials.

  Examples of the negative electrode active material for a lithium ion secondary battery include a carbon-based negative electrode active material, a metal-based negative electrode active material, and a negative electrode active material combining these.

  Here, the carbon-based negative electrode active material refers to an active material having lithium as a main skeleton into which lithium can be inserted (also referred to as “dope”). Examples of the carbon-based negative electrode active material include a carbonaceous material and graphite. Quality materials.

Examples of the carbonaceous material include easily graphitizable carbon and non-graphitizable carbon having a structure close to an amorphous structure represented by glassy carbon.
Here, examples of the graphitizable carbon include a carbon material obtained from tar pitch obtained from petroleum or coal as a raw material. Specific examples include coke, mesocarbon microbeads (MCMB), mesophase pitch-based carbon fibers, and pyrolytic vapor grown carbon fibers.
Examples of the non-graphitizable carbon include a fired phenol resin, a polyacrylonitrile-based carbon fiber, pseudo isotropic carbon, a furfuryl alcohol resin fired body (PFA), and hard carbon.

Furthermore, examples of the graphite material include natural graphite and artificial graphite.
Here, as the artificial graphite, for example, artificial graphite in which carbon including easily graphitizable carbon is mainly heat-treated at 2800 ° C. or higher, graphitized MCMB in which MCMB is heat-treated at 2000 ° C. or higher, and mesophase pitch-based carbon fiber are 2000 ° C. Examples include the graphitized mesophase pitch-based carbon fiber that has been heat-treated as described above.

  Further, the metal-based negative electrode active material is an active material containing a metal, and usually has a structure including an element capable of inserting lithium, and has a theoretical electric capacity of 500 mAh / unit mass per unit mass when lithium is inserted. An active material having a weight of at least g. Examples of the metal-based active material include a lithium metal and a simple metal capable of forming a lithium alloy (eg, Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, P, Pb, Sb, Si, Sn). , Sr, Zn, Ti, etc.) and their alloys, and their oxides, sulfides, nitrides, silicides, carbides, phosphides, and the like. Among these, the metal-based negative electrode active material is preferably an active material containing silicon (silicon-based negative electrode active material). This is because it is possible to increase the capacity of the lithium-ion secondary battery by using the silicon-based negative electrode active material.

Examples of the silicon-based negative electrode active material include silicon (Si), alloys containing silicon, SiO, SiO _x , and a composite of a Si-containing material and a conductive carbon obtained by coating or compositing a Si-containing material with conductive carbon. And so on. These silicon-based negative electrode active materials may be used alone or in combination of two or more.
The amount and particle size of the negative electrode active material are not particularly limited, and may be the same as those of conventionally used negative electrode active materials.

<Binder composition>
As the binder composition, the binder composition for electrochemical device electrodes of the present invention containing the above-mentioned polymer is used.

  Here, the content ratio of the binder composition in the electrochemical device electrode slurry composition is preferably such that the amount of the polymer is 0.5 parts by mass or more per 100 parts by mass of the electrode active material. The amount is preferably at least 0.0 part by mass, more preferably at least 1.5 parts by mass, still more preferably at most 4.0 parts by mass, and at most 3.0 parts by mass. It is more preferable that the amount is less than or equal to parts, and further preferable that the amount is less than or equal to 2.5 parts by mass. When the binder composition is contained in the slurry composition in an amount such that the amount of the polymer is 0.5 parts by mass or more, the electrode mixture layer can be more firmly adhered to the current collector. On the other hand, when the binder composition is contained in the slurry composition so that the amount of the polymer is 4.0 parts by mass or less, the ratio of the electrode active material in the electrode mixture layer is secured, and the electrochemical composition is maintained. The capacity of the element can be sufficiently increased.

<Other ingredients>
The other components that can be blended in the slurry composition are not particularly limited, and the same as the other components that can be blended in the binder composition described above can be mentioned. Further, other components may be used alone or in combination of two or more at an arbitrary ratio.

<Preparation of slurry composition>
The slurry composition described above can be prepared by mixing the above components. Specifically, using a mixer such as a ball mill, a sand mill, a bead mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, a planetary mixer, and a fill mix, the above components and any of them are arbitrarily added. A slurry composition can be prepared by mixing with a solvent. In addition, as the solvent optionally added when preparing the slurry composition, the same solvent as described in the section of the binder composition can be used.

(Electrode for electrochemical device)
The electrode for electrochemical device of the present invention is provided with, for example, an electrode mixture layer formed on the collector by using the above-mentioned slurry composition for electrochemical device electrode. Specifically, the electrode mixture layer is usually composed of a dried product of the above-described electrochemical device electrode slurry composition, and the electrode mixture layer includes at least an electrode active material and the above-mentioned polymer, and optionally. , And other ingredients are contained. Each component contained in the electrode mixture layer was one contained in the slurry composition for electrochemical device electrodes, and a suitable abundance ratio of each component is in the slurry composition. It is the same as the preferable abundance ratio of each component.
In the electrode for electrochemical device of the present invention, since the electrode mixture layer is formed by using the above-mentioned slurry composition for electrochemical device electrode, an electrochemical device is manufactured using the electrode for electrochemical device. When manufactured, an electrochemical device having a high capacity and excellent cycle characteristics can be obtained.

(Method of manufacturing electrode for electrochemical device)
The above-mentioned electrode for electrochemical device of the present invention can be produced, for example, by using the method for producing an electrode for electrochemical device of the present invention.
The method for producing an electrode of the present invention comprises a step of applying the above-described slurry composition of the present invention on a current collector (application step), and drying the slurry composition applied on the current collector to collect current. A step of forming a pre-pressing electrode mixture layer on the body (drying step), and a pre-pressing electrode mixture layer is roll-pressed at a linear pressure of 500 kN / cm or more and 3000 kN / cm or less to obtain a post-pressing electrode mixture layer. And a step of obtaining (pressing step).

<Coating process>
The method for applying the slurry composition onto the current collector is not particularly limited, and a known method can be used. Specifically, as a coating method, a doctor blade method, a dipping method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, a brush coating method or the like can be used. At this time, the slurry composition may be applied to only one surface of the current collector, or may be applied to both surfaces. The thickness of the slurry film on the current collector after coating and before drying can be appropriately set according to the desired thickness of the electrode mixture layer.

  Here, as the current collector for applying the slurry composition, a material having electrical conductivity and electrochemical durability is used. Specifically, as the current collector, for example, a current collector made of iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, platinum, or the like can be used. In addition, the said material may be used individually by 1 type and may be used in combination of 2 or more types by arbitrary ratios.

<Drying process>
The method for drying the slurry composition on the current collector is not particularly limited, and known methods can be used, for example, hot air, hot air, low-humid air drying methods, vacuum drying methods, infrared rays, electron beams, and the like. A drying method by irradiation can be mentioned. By drying the slurry composition on the current collector in this manner, the pre-press electrode mixture layer can be formed on the current collector.

<Press process>
The linear pressure at the time of roll-pressing the electrode mixture layer before pressing on the current collector needs to be 500 kN / cm or more and 3000 kN / cm or less, preferably 1000 kN / cm or more, and 2500 kN / cm. The following is preferable. Since the pre-pressing electrode mixture layer on the current collector is formed from the slurry composition of the present invention, it is easily compressed at a linear pressure of 500 kN / cm or more to obtain a high density post-pressing electrode mixture material. Layers can be obtained. When the linear pressure is 3000 kN / cm or less, the electrode active material will not be excessively destroyed by the pressing.
The roll temperature at the time of roll pressing is usually 25 ° C. or higher and 150 ° C. or lower. Further, the conveyance speed of the laminate of the electrode mixture layer before pressing and the current collector during roll pressing is usually 5 m / min or more and 100 m / min or less. The number of roll presses may be plural, but it is usually once.

(Electrochemical element)
The electrochemical device of the present invention is not particularly limited and is a lithium ion secondary battery or an electric double layer capacitor, preferably a lithium ion secondary battery. Since the electrochemical device of the present invention includes the electrode for an electrochemical device of the present invention, it has high capacity and excellent cycle characteristics.

  Here, a case where the electrochemical element is a lithium ion secondary battery will be described below as an example, but the present invention is not limited to the following example. A lithium ion secondary battery as an electrochemical device of the present invention is usually provided with an electrode (positive electrode and negative electrode), an electrolytic solution, and a separator, and the electrode for electrochemical device of the present invention is used for at least one of the positive electrode and the negative electrode. .

<Electrode>
Here, as the electrodes other than the above-mentioned electrodes for electrochemical devices that can be used in the lithium ion secondary battery as the electrochemical device of the present invention, known electrodes can be used without particular limitation. Specifically, as an electrode other than the above-mentioned electrode for electrochemical device, an electrode formed by forming an electrode mixture layer on a current collector by using a known manufacturing method can be used.

<Electrolyte>
As the electrolytic solution, an organic electrolytic solution prepared by dissolving a supporting electrolyte in an organic solvent is usually used. For example, a lithium salt is used as the supporting electrolyte of the lithium ion secondary battery. Examples of the lithium salt include LiPF ₆ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAlCl ₄ , LiClO ₄ , CF ₃ SO ₃ Li, C ₄ F ₉ SO ₃ Li, CF ₃ COOLi, (CF ₃ CO) ₂ NLi. , (CF ₃ SO ₂ ) ₂ NLi, (C ₂ F ₅ SO ₂ ) NLi, and the like. Among them, LiPF ₆ , LiClO ₄ , and CF ₃ SO ₃ Li are preferable, and LiPF ₆ is particularly preferable, because it is easily dissolved in a solvent and exhibits a high dissociation degree. The electrolytes may be used alone or in combination of two or more at an arbitrary ratio. Generally, the higher the dissociation degree of the supporting electrolyte, the higher the lithium ion conductivity tends to be, so the lithium ion conductivity can be adjusted by the type of the supporting electrolyte.

The organic solvent used in the electrolytic solution is not particularly limited as long as it can dissolve the supporting electrolyte, and examples thereof include dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), Carbonates such as butylene carbonate (BC) and ethylmethyl carbonate (EMC); Esters such as γ-butyrolactone and methyl formate; Ethers such as 1,2-dimethoxyethane and tetrahydrofuran; Sulfur-containing compounds such as sulfolane and dimethyl sulfoxide And the like are preferably used. Moreover, you may use the mixed liquid of these solvents. Among them, it is preferable to use carbonates, and it is more preferable to use a mixture of ethylene carbonate and ethylmethyl carbonate, since they have a high dielectric constant and a wide stable potential region.
Further, known additives such as vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethyl methyl sulfone and the like may be added to the electrolytic solution.

<Separator>
The separator is not particularly limited, and for example, those described in JP 2012-204303 A can be used. Among these, it is possible to reduce the film thickness of the entire separator, and thereby, the ratio of the electrode active material in the lithium ion secondary battery can be increased and the capacity per volume can be increased. A microporous membrane made of a system (polyethylene, polypropylene, polybutene, polyvinyl chloride) resin is preferable.

<Method for manufacturing lithium-ion secondary battery>
The lithium-ion secondary battery as the electrochemical device of the present invention is, for example, a positive electrode and a negative electrode are stacked via a separator, and the battery container is formed by winding and folding the positive electrode and the negative electrode according to the shape of the battery as needed. It can be manufactured by pouring the solution into a battery container, injecting an electrolytic solution into the battery container, and sealing the container. If necessary, a fuse, an overcurrent preventing element such as a PTC element, an expanded metal, a lead plate, etc. may be provided in order to prevent an increase in internal pressure of the lithium-ion secondary battery and the occurrence of overcharging and discharging. . The lithium ion secondary battery may have any shape such as a coin shape, a button shape, a sheet shape, a cylinder shape, a square shape, and a flat shape.

Hereinafter, the present invention will be specifically described based on Examples, but the present invention is not limited to these Examples. In the following description, “%” and “part” representing the amount are based on mass unless otherwise specified.
In Examples and Comparative Examples, the electrolytic solution swelling degree of the polymer, the peel strength of the positive electrode, the density of the positive electrode mixture layer before pressing (coating density), the density of the positive electrode mixture layer after pressing (press density), and lithium ion The cycle characteristics of the secondary battery were evaluated by the following method. The evaluation results are shown in Table 1.

<Electrolyte swelling degree of polymer>
The positive electrode binder composition (polymer NMP solution) is applied on a polytetrafluoroethylene sheet and dried in an environment of a temperature of 80 to 120 ° C. for 0.5 to 3 hours, and cast with a thickness of 500 μm ± 50 μm. I got a film. This cast film was cut into a 1 cm × 1 cm square to obtain a test piece, and the mass of the test piece (mass A before immersion) was measured. Then, the test piece was immersed in an electrolytic solution at a temperature of 60 ° C. for 72 hours. The electrolytic solution was prepared by adding FEC to a mixture of EC: EMC = 3: 7 (weight basis) so that the concentration was 5% by mass, and then adding LiPF ₆ to the mixture after adding FEC to have a concentration of 1.0M. Was dissolved, and vinylene carbonate was added to the mixture after dissolution of LiPF ₆ so that the concentration was 2% by mass. The test piece after immersion was pulled up, the electrolytic solution on the surface was wiped off with a towel paper, and then the mass of the test piece (mass B after immersion) was measured.
Then, the electrolytic solution swelling degree (%) was calculated using the following calculation formula. A polymer having a lower degree of swelling in the electrolytic solution is more likely to retain the binding property in the electrolytic solution and can exhibit excellent characteristics (particularly, cycle characteristics) in the electrochemical device.
Electrolyte swelling degree (%) = mass B after immersion / mass A before immersion × 100
<Peel strength of positive electrode>
The positive electrode was cut into a rectangular shape with a width of 1.0 cm and a length of 10 cm to obtain a test piece, and the test piece was fixed on a horizontal table with the positive electrode mixture layer facing upward. Then, after the cellophane tape was attached to the surface of the positive electrode mixture layer of the test piece, the stress was measured when the cellophane tape was peeled from one end of the test piece in the 180 ° direction at a speed of 50 mm / min. At this time, the cellophane tape specified in JIS Z1522 was used. The measurement was performed 10 times, the average value of the obtained values was taken as the peel strength (N / m), and the evaluation was made according to the following criteria. The higher the peel strength, the more firmly the positive electrode mixture layer is in close contact with the current collector.
A: Peel strength is 70 N / m or more B: Peel strength is 50 N / m or more and less than 70 N / m C: Peel strength is 30 N / m or more and less than 50 N / m D: Peel strength is 10 N / m or more and less than 30 N / m E: Peel strength less than 10 N / m <Density of positive electrode mixture layer before pressing (application density)>
The coating density (g / cm ³ ) was calculated from the thickness (cm) and the coating amount (g / cm ² ) of the positive electrode composite material layer of the positive electrode raw material before pressing using the following formula. The thickness of the positive electrode mixture layer before pressing was measured with a micrometer. The higher the coating density (that is, the higher the density of the positive electrode composite material layer before pressing), the easier it is to form a high density positive electrode composite material layer by roll pressing.
Coating density (g / cm ³ ) = Coating amount (g / cm ² ) / Thickness (cm)
A: the coating density of 2.5 g / cm ³ or more B: the coating density of 2.4 g / cm ³ or more 2.5 g / cm ³ less C: less than the coating density of 2.3 g / cm ³ or more 2.4 g / cm ³ D: Coating density is less than 2.3 g / cm ³ <Density of positive electrode after pressing (press density)>
The positive electrode raw material was punched into a circle having a diameter of 1.2 cm to obtain a test piece. This test piece was placed on a flat plate and pressed at a pressure of 9 MPa (press test). Then, after pressing, the thickness (cm) and the weight (g) of the positive electrode mixture layer were obtained, and the density of the electrode mixture layer was calculated. The thickness of the positive electrode mixture layer after pressing was measured with a micrometer. The weight of the positive electrode composite material layer after pressing was calculated by subtracting the weight of the current collector from the weight of the test piece after pressing. This press test was performed 10 times, and the average value of the obtained values was defined as the press density (g / cm ³ ) and evaluated according to the following criteria. It is shown that the higher the press density is, the more excellent the compressibility of the positive electrode composite material layer before pressing is, and the higher density the positive electrode composite material layer can be easily formed by roll pressing.
A: press density is 3.8 g / cm ³ or more B: press density is 3.7 g / cm ³ or more 3.8 g / cm ³ less C: less than the press density of 3.6 g / cm ³ or more 3.7 g / cm ³ D: Press density is 3.5 g / cm ³ or more and less than 3.6 g / cm ³ E: Press density is less than 3.5 g / cm ³ <Cycle characteristics of lithium ion secondary battery>
The obtained lithium ion secondary battery was aged at a SOC (State of Charge) of 10% and 60 ° C. for 10 hours. After aging, the operation of charging at 0.2 C until the voltage reached 4.2 V and discharging at 0.2 C until the voltage reached 3.0 V was repeated 3 times. Then, with respect to this lithium-ion secondary battery, under a 45 ° C. environment, the operation of charging at 1 C until the voltage became 4.2 V and discharging at 1 C until the voltage became 3.0 V was repeated 100 times. Then, the ratio of the discharge capacity at the end of 100 cycles to the discharge capacity at the end of 1 cycle is the capacity retention rate (%) (= {(discharge capacity at the end of 100 cycles) / (discharge capacity at the end of 1 cycle)} × 100) and evaluated according to the following criteria. The larger the capacity retention rate, the better the cycle characteristics.
A: Capacity retention rate is 84% or more B: Capacity retention rate is 82% or more and less than 84% C: Capacity retention rate is 80% or more and less than 82% D: Capacity retention rate is 77% or more and less than 80% E: Capacity retention rate Is less than 77%

(Example 1)
<Preparation of polymer and binder composition for positive electrode>
In a reactor, 10.0 parts of 1,3-butadiene and 20.0 parts of isoprene as an aliphatic conjugated diene monomer, 70.0 parts of acrylonitrile as a nitrile group-containing monomer, and t-dodecyl mercaptan 0.4. Parts, ion-exchanged water 132 parts, sodium dodecylbenzenesulfonate 3 parts, β-naphthalenesulfonic acid formalin condensate sodium salt 0.5 parts, potassium persulfate 0.3 parts, and ethylenediaminetetraacetic acid sodium salt 0.05 parts Was charged, polymerization was carried out while maintaining the polymerization temperature at 15 ° C., and the reaction was continued until the polymerization conversion rate reached 94%. Then, the contents were returned to room temperature, the system was made a nitrogen atmosphere, and then concentrated using an evaporator until the solid content concentration became 40% to obtain an aqueous dispersion of the polymer.
320 parts of NMP was added to 100 parts of the aqueous dispersion of this polymer, and then the solvent was replaced by evaporating water under reduced pressure to obtain an NMP solution of the polymer (a binder composition for a positive electrode).
After coagulating 100 g of the obtained polymer NMP solution with 1 L of methanol, it was vacuum dried at 60 ° C. overnight to obtain a dried body. This dried product was analyzed by the NMR method, and it was confirmed that the polymer contained 70% of acrylonitrile units, 10% of 1,3-butadiene units and 20% of isoprene units.
<Preparation of slurry composition for positive electrode>
96 parts of Li (Ni _0.5 Co _0.2 Mn _0.3 ) O ₂ (average particle size: 10 μm) as a positive electrode active material, and acetylene black (a product name “HS” manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive material. -100 "), 2.0 parts of the above-mentioned positive electrode binder composition (solid content concentration: 8.0%) in terms of solid content, and an appropriate amount of NMP as an additional solvent in a planetary mixer. In addition, a positive electrode slurry composition was prepared by mixing with the mixer.
<Production of positive electrode>
An aluminum foil having a thickness of 20 μm was prepared as a current collector. The positive electrode slurry composition prepared as described above was applied to one surface of the aluminum foil so that the applied amount after drying was about 22 mg / cm ² . Then, the coating film on the aluminum foil was dried at 80 ° C. for 20 minutes and 120 ° C. for 20 minutes, and then heat-treated at 150 ° C. for 2 hours to obtain a positive electrode raw material sheet including a negative electrode mixture layer before pressing and a current collector. It was This positive electrode raw material was roll-pressed at a linear pressure of 2000 kN / cm to produce a positive electrode having a positive electrode mixture layer having a density of 3.7 g / cm ³ on one surface of the current collector.
<Production of negative electrode>
A mixture of 90 parts of spherical artificial graphite (volume average particle size: 12 μm) and 10 parts of SiO _x (volume average particle size: 10 μm) as a negative electrode active material, and styrene-butadiene rubber (number average particle size: 180 nm) as a binder. , Glass transition temperature: 10 ° C.), 1 part of carboxymethyl cellulose as a thickening agent, and an appropriate amount of water were stirred with a planetary mixer to prepare a slurry composition for a negative electrode.
Next, a copper foil having a thickness of 15 μm was prepared as a current collector. The negative electrode slurry composition prepared as described above was applied to one surface of the copper foil so that the applied amount after drying was 12 mg / cm ² . Then, the coating film on the copper foil was dried at 50 ° C. for 20 minutes and 110 ° C. for 20 minutes, and then heat-treated at 150 ° C. for 2 hours to obtain a negative electrode raw material. This negative electrode raw material was rolled by a roll press to prepare a negative electrode having a negative electrode mixture layer having a density of 1.8 g / cm ³ on one surface of a current collector.
<Preparation of lithium-ion secondary battery>
The produced positive electrode and negative electrode were wound using a core having a diameter of 20 mm with a separator (microporous polypropylene film) having a thickness of 20 μm interposed therebetween to obtain a wound body. The positive electrode and the negative electrode were arranged so that the positive electrode composite material layer and the negative electrode composite material layer face each other with the separator interposed therebetween. Then, the obtained wound body was compressed from one direction at a speed of 10 mm / sec until the thickness became 4.5 mm. The wound body after compression had an elliptical shape in plan view, and the ratio of the major axis to the minor axis (major axis / minor axis) was 7.7.
Separately, FEC was added to a mixture of EC: EMC = 3: 7 (weight basis) so that the concentration was 5% by mass. Next, LiPF ₆ was dissolved in the mixture after the addition of FEC to a concentration of 1.0M. Then, an electrolyte solution was prepared by adding vinylene carbonate to the mixture after dissolving LiPF ₆ so that the concentration was 2% by mass.
Then, the compressed wound body was accommodated in an aluminum laminate case together with 3.2 g of the electrolytic solution. Then, a lead wire was connected to a predetermined part of the negative electrode and a lead wire was connected to a predetermined part of the positive electrode, and then the opening of the case was sealed with heat to obtain a lithium ion secondary battery. This lithium-ion secondary battery was a pouch type with a width of 35 mm, a height of 48 mm, and a thickness of 5 mm, and the nominal capacity of the battery was 720 mAh.

(Examples 2 to 7)
NMP solution of the polymer (positive electrode binder composition), positive electrode slurry composition, positive electrode, negative electrode, in the same manner as in Example 1 except that the monomer composition shown in Table 1 was adopted when preparing the polymer. , And a lithium-ion secondary battery were produced. The analysis by the NMR method was carried out in the same manner as in Example 1, and the ratio of a certain monomer unit in the polymer accounted for in the total monomer used for the polymerization of the polymer. It was confirmed that the ratio was the same as the ratio (preparation ratio).

(Comparative Examples 1-2)
NMP solution of the polymer (positive electrode binder composition), positive electrode slurry composition, positive electrode, negative electrode, in the same manner as in Example 1 except that the monomer composition shown in Table 1 was adopted when preparing the polymer. , And a lithium-ion secondary battery were produced. The analysis by the NMR method was carried out in the same manner as in Example 1, and the ratio of a certain monomer unit in the polymer accounted for in the total monomer used for the polymerization of the polymer. It was confirmed that the ratio was the same as the ratio (preparation ratio).

(Comparative example 3)
An aqueous dispersion of the polymer was prepared in the same manner as in Example 1 except that the monomer composition shown in Table 1 was adopted when the polymer was prepared. Then, the solvent substitution with NMP was carried out in the same manner as in Example 1, but the polymer did not dissolve in NMP. Since it was clear that a lithium ion secondary battery exhibiting excellent performance could not be obtained even by using such a binder composition for a positive electrode, a positive electrode, a negative electrode, and a lithium ion secondary battery were not manufactured. . The evaluation of the degree of electrolytic solution swelling of the polymer was performed. In addition, an analysis by an NMR method was performed in the same manner as in Example 1, and the ratio of a certain monomer unit in the polymer occupied in all the monomers used in the polymerization of the polymer was the certain monomer. It was confirmed that the ratio was the same as the ratio (preparation ratio).

From Table 1, in Examples 1 to 7 using a binder composition containing a polymer containing a nitrile group-containing monomer unit and two kinds of aliphatic conjugated diene monomer units, while increasing the coating density, It can be seen that the electrode composite material layer can be sufficiently densified. In addition, in Examples 1 to 7, it can be seen that the electrode mixture layer can be firmly adhered to the current collector to allow the lithium ion secondary battery to exhibit sufficiently excellent cycle characteristics.
On the other hand, in Comparative Example 1 in which a binder composition containing a polymer containing a nitrile group-containing monomer unit but containing only 1,3-butadiene units as an aliphatic conjugated diene monomer unit was used, an electrode mixture was prepared. It can be seen that it is difficult to densify the layers.
Further, in Comparative Example 2 in which a binder composition containing a polymer containing a nitrile group-containing monomer unit but containing only an isoprene unit as an aliphatic conjugated diene monomer unit was used, a high density of the electrode mixture layer was obtained. It turns out that it is difficult to make it.
Then, in Comparative Example 3 using a binder composition containing a polymer containing two kinds of aliphatic conjugated diene monomer units, but not containing a nitrile group-containing monomer unit, as described above, the polymer was The positive electrode, the negative electrode, and the lithium ion secondary battery were not manufactured because they did not dissolve in NMP.

ADVANTAGE OF THE INVENTION According to this invention, the binder composition for electrochemical device electrodes and the slurry composition for electrochemical device electrodes which can make the said electrode composite material layer stick firmly to a collector, densifying an electrode composite material layer easily. Can be provided.
Further, according to the present invention, it is possible to provide an electrochemical device electrode having a high capacity and capable of exhibiting excellent cycle characteristics in the electrochemical device, and a method for producing the electrochemical device electrode. You can
Furthermore, according to the present invention, it is possible to provide an electrochemical device having a high capacity and excellent cycle characteristics.

Claims (12)

A binder composition for an electrochemical device electrode containing a polymer,
A binder composition for an electrochemical device electrode, wherein the polymer contains a nitrile group-containing monomer unit and at least two kinds of aliphatic conjugated diene monomer units.   The binder composition for an electrochemical device electrode according to claim 1, wherein the aliphatic conjugated diene monomer unit includes an aliphatic conjugated diene monomer unit having 5 to 12 carbon atoms.   The binder composition for an electrochemical device electrode according to claim 2, wherein a ratio of the aliphatic conjugated diene monomer unit having 5 to 12 carbon atoms in the polymer is 1% by mass to 50% by mass. object.   The binder composition for an electrochemical device electrode according to claim 1, wherein the aliphatic conjugated diene monomer unit contains a 1,3-butadiene unit.   The binder composition for electrochemical device electrodes according to claim 4, wherein the ratio of the 1,3-butadiene unit in the polymer is 1% by mass or more and 50% by mass or less.   The binder composition for an electrochemical element electrode according to claim 1, wherein a ratio of the nitrile group-containing monomer unit in the polymer is 20% by mass or more and 85% by mass or less.   The aliphatic conjugated diene monomer unit contains an aliphatic conjugated diene monomer unit having 5 or more and 12 or less carbon atoms and a 1,3-butadiene unit, and the 1,3-butadiene unit in the polymer is The electrochemical element electrode according to any one of claims 1 to 6, wherein the ratio of the ratio of the aliphatic conjugated diene monomer unit having 5 to 12 carbon atoms to the ratio is 0.02 to 50. Binder composition.   A slurry composition for an electrochemical device electrode, comprising an electrode active material and the binder composition for an electrochemical device electrode according to claim 1.   The slurry composition for an electrochemical element electrode according to claim 8, wherein the electrode active material is an electrode active material containing nickel.   An electrode for an electrochemical device, comprising an electrode mixture layer formed using the slurry composition for an electrochemical device electrode according to claim 8 or 9.   An electrochemical device comprising the electrode for an electrochemical device according to claim 10. Applying a slurry composition for an electrochemical device electrode according to claim 8 or 9 onto a current collector;
Drying the electrochemical device electrode slurry composition applied on the current collector to form a pre-press electrode mixture layer on the current collector;
Roll-pressing the electrode mixture layer before pressing at a linear pressure of 500 kN / cm or more and 3000 kN / cm or less to obtain an electrode mixture layer after pressing,
Manufacturing method of electrode for electrochemical device.