JP7156281B2 - Binder composition for electrochemical element electrode, slurry composition for electrochemical element electrode, electrode for electrochemical element, electrochemical element, and method for producing electrode for electrochemical element - Google Patents

Description

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

Electrochemical devices such as lithium ion secondary batteries and electric double layer capacitors are small, 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, this electrode mixture layer is formed by, for example, applying a slurry composition containing an electrode active material and a binder composition containing a binder onto 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, a hydrogenated carboxy-modified rubber is used as a binder to prepare a negative electrode for a lithium ion secondary battery, thereby increasing the negative electrode peel strength and improving the high rate discharge characteristics of the lithium ion secondary battery. It improves cycle characteristics.
In Patent Document 2, a battery electrode plate is produced using a carboxy-modified rubber as a binder and a base as a dispersant, thereby increasing the peel strength of the battery electrode plate and improving the cycle characteristics of the battery. are improving.

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

Here, in recent years, electrochemical devices are required to have even higher capacities. In order to increase the capacity of an 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 large thickness. However, when forming an electrode mixture layer using the conventional binder composition, it is difficult to achieve a sufficient density even if a press treatment is performed to achieve a high density of the electrode mixture layer. Met.
Further, when forming the electrode mixture layer using the conventional binder composition, if the thickness of the electrode mixture layer is increased, components such as the electrode active material contained in the electrode mixture layer are removed from the electrode mixture layer. There is also a problem that it becomes easy to detach. If an electrode having such an electrode mixture layer is used, the cycle characteristics of the electrochemical device may be impaired.
That is, the above-described conventional binder composition has room for improvement in terms of easily increasing the density of the electrode mixture layer and firmly adhering the electrode mixture layer 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 that can easily increase the density of the electrode mixture layer and firmly adhere the electrode mixture layer to the current collector. intended to provide
Another object of the present invention is to provide an electrode for an electrochemical device that can increase the capacity of the electrochemical device and that can exhibit excellent cycle characteristics in the electrochemical device, and a method for producing the electrode for the electrochemical device. and
A further object of the present invention is to provide an electrochemical device that has a high capacity and excellent cycle characteristics.

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

That is, an object of the present invention is to advantageously solve the above problems, and a binder composition for an electrochemical element electrode of the present invention is a binder composition for an electrochemical element electrode containing a polymer. The polymer comprises a nitrile group-containing monomer unit and at least two aliphatic conjugated diene monomer units. By using the binder composition containing the polymer having the composition described above, the electrode mixture layer can be easily densified and firmly adhered to the current collector. Then, by using an electrode comprising an electrode mixture layer obtained using a binder composition containing a polymer having the above composition, the electrochemical device can have a high capacity and excellent cycle characteristics of the electrochemical device. can be demonstrated.
In the present invention, "containing a monomer unit" means "a repeating unit derived from the monomer is contained in the polymer obtained using the monomer".

Here, in the binder composition for an electrochemical element electrode of the present invention, the aliphatic conjugated diene monomer unit preferably contains an aliphatic conjugated diene monomer unit having from 5 to 12 carbon atoms. If the polymer contains a repeating unit derived from an aliphatic conjugated diene monomer having 5 to 12 carbon atoms as the aliphatic conjugated diene monomer unit, the electrode mixture layer can be easily increased in density and current collection. Strong adhesion to the body can be achieved at even higher levels.

Further, in the binder composition for an electrochemical element electrode of the present invention, the ratio of the aliphatic conjugated diene monomer unit having 5 to 12 carbon atoms in the polymer is 1 to 50 mass%. Preferably. If the polymer contains aliphatic conjugated diene monomer units having 5 or more and 12 or less carbon atoms in the above ratio, it is possible to easily increase the density of the electrode mixture layer and firmly adhere to the current collector. can be achieved at a high level.
In the present invention, in the polymer produced by copolymerizing a plurality of types of monomers, the "proportion of monomer units" formed by polymerizing a certain monomer is usually the weight It corresponds to the ratio (feed ratio) of the certain monomer to the total monomers used for the polymerization of the coalescence. Further, in the present invention, the "proportion of monomer units" in the polymer can be measured using nuclear magnetic resonance (NMR) methods such as ¹ H-NMR and ¹³ C-NMR.

In the binder composition for electrochemical element electrodes of the present invention, the aliphatic conjugated diene monomer unit preferably contains a 1,3-butadiene unit. If the polymer contains repeating units derived from 1,3-butadiene as aliphatic conjugated diene monomer units, the electrode mixture layer can be more easily densified.

Furthermore, in the binder composition for an electrochemical element 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. If the polymer contains 1,3-butadiene units in the above ratio, it is possible to easily increase the density of the electrode mixture layer and achieve a higher level of strong adhesion to the current collector.

Here, in the binder composition for electrochemical element electrodes of the present invention, the proportion 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 ratio, it is possible to easily increase the density of the electrode mixture layer and achieve a higher level of firm adhesion to the current collector. In addition, the affinity of the polymer for organic solvents (in particular, polar organic solvents such as N-methylpyrrolidone) is ensured, and a binder composition in which the polymer is well dissolved in the organic solvent can be obtained.

Further, in the binder composition for an electrochemical element electrode of the present invention, the aliphatic conjugated diene monomer unit includes an aliphatic conjugated diene monomer unit having 5 to 12 carbon atoms and a 1,3-butadiene unit. and 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 aliphatic conjugated diene monomer units having 5 to 12 carbon atoms and 1,3-butadiene units, and the number of carbon atoms is 5 or more relative to the ratio of 1,3-butadiene units in the polymer. If the ratio of the ratio of the aliphatic conjugated diene monomer units of 12 or less is within the above range, the electrode mixture layer can be easily densified and the strong adhesion to the current collector can be achieved at a higher level. can do.

Another object of the present invention is to advantageously solve the above-described problems, and the slurry composition for an electrochemical element electrode of the present invention comprises an electrode active material and the binder composition for an electrochemical element electrode described above. characterized by including any of Thus, by forming the electrode mixture layer using a slurry composition containing any of the binder compositions described above, the electrode mixture layer can be easily densified and firmly adhered to the current collector. be able to. By using an electrode having an electrode mixture layer obtained using the slurry composition described above, the capacity of the electrochemical device can be increased, and excellent cycle characteristics can be exhibited by the electrochemical device.

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

Another object of the present invention is to advantageously solve the above-described problems, and an electrode for an electrochemical device of the present invention is formed using any of the slurry compositions for an electrochemical device electrode described above. It is characterized by comprising an electrode mixture layer. As described above, by using any of the slurry compositions described above, it is possible to produce an electrode capable of increasing the capacity of the electrochemical element and allowing the electrochemical element to exhibit excellent cycle characteristics.

Another object of the present invention is to advantageously solve the above-described problems, and an electrochemical device of the present invention is characterized by comprising the electrode for an electrochemical device described above. Thus, by using the electrode for an electrochemical device described above, an electrochemical device having a high capacity and excellent cycle characteristics can be obtained.

An object of the present invention is to advantageously solve the above-described problems. A method for producing an electrode for an electrochemical element according to the present invention comprises collecting any of the above slurry compositions for an electrode for an electrochemical element. A step of applying onto a current collector, and a step of drying the electrochemical element electrode slurry composition applied onto the current collector to form a pre-pressing electrode mixture layer on the current collector; and a step of roll-pressing the pre-pressed electrode mixture layer at a linear pressure of 500 kN/cm or more and 3000 kN/cm or less to obtain a post-press electrode mixture layer. By adopting the procedure described above using any of the slurry compositions described above, the electrode mixture layer can be sufficiently densified and firmly adhered to the current collector.
In the present invention, the “linear pressure” is a value obtained by dividing the load (kN) applied to the electrode mixture layer before pressing during roll pressing by the width (cm) of the electrode mixture layer before pressing. is.

According to the present invention, a binder composition for an electrochemical element electrode and a slurry composition for an electrochemical element electrode, which can easily increase the density of the electrode mixture layer and firmly adhere the electrode mixture layer to the current collector. can be provided.
Further, according to the present invention, there is provided an electrode for an electrochemical element which can increase the capacity of the electrochemical element and which can exhibit excellent cycle characteristics in the electrochemical element, and a method for producing the electrode for the electrochemical element. can be done.
Furthermore, according to the present invention, it is possible to provide an electrochemical device that has a high capacity and excellent cycle characteristics.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail.
Here, the binder composition for electrochemical element electrodes of the present invention can be used when preparing the slurry composition for electrochemical element electrodes of the present invention. Then, the slurry composition for an electrochemical element electrode of the present invention prepared using the binder composition for an electrochemical element electrode of the present invention is prepared by, for example, using the method for producing an electrode for an electrochemical element of the present invention. It can be used when producing an electrode for an electrochemical device of the invention. Furthermore, the electrochemical device of the present invention is characterized by using the electrode for an electrochemical device of the present invention produced using the slurry composition for an electrochemical device electrode of the present invention.

(Binder composition for electrochemical element electrode)
The binder composition of the present invention contains a polymer and optionally further contains other ingredients that can be incorporated into the electrode of an electrochemical device. Moreover, the binder composition of the present invention can further contain a solvent. Here, the polymer contained in the binder composition of the present invention contains a nitrile group-containing monomer unit and at least two aliphatic conjugated diene monomer units.
Since the binder composition of the present invention contains the polymer described above as a binder, if the electrode mixture layer of the electrode for an electrochemical element is formed using the binder composition, the electrode mixture The layer can be easily densified and adhered strongly to the current collector.
The reason why it is possible to easily increase the density of the electrode mixture layer and achieve strong adhesion to the current collector by using the binder composition of the present invention is not clear, but it is as follows. guessed.
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 by using two or more kinds of aliphatic conjugated diene monomers instead of one kind alone, the polymer is a compounding component such as an electrode active material and a conductive material (Particularly, carbon-based materials) are enhanced, and these ingredients can be well dispersed in the slurry composition prepared using the binder composition. By coating the current collector with the slurry composition in which the ingredients are well dispersed in this way, a high coating density can be achieved. Furthermore, according to a slurry composition containing a polymer that is excellent in flexibility and capable of well dispersing the ingredients, the components are not unevenly distributed during the formation of the electrode mixture layer, and, for example, relatively low linearity is achieved. Even in the case of roll pressing with pressure, the density of the obtained electrode mixture layer can be sufficiently increased, and the electrode mixture layer can be adhered well to the current collector. In addition, the polymer contained in the binder composition of the present invention contains not only the above-described aliphatic conjugated diene monomer units but also nitrile group-containing monomer units, and therefore has excellent strength. Since a polymer having such excellent strength exhibits high binding properties, the use of a binder composition containing the polymer allows the electrode mixture layer to be firmly adhered to the current collector.

<Polymer>
The polymer prevents components contained in the electrode mixture layer from detaching from the electrode mixture layer in the electrode produced by forming the electrode mixture layer using the slurry composition prepared using the binder composition. (that is, it functions as a binding material).

<<Polymer composition>>
The polymer comprises nitrile group-containing monomeric units and at least two aliphatic conjugated diene monomeric units. That is, the polymer contains repeating units derived from at least one nitrile group-containing monomer and repeating units derived from at least two aliphatic conjugated diene monomers.
The polymer A can optionally contain repeating units (other repeating units) other than the nitrile group-containing monomer units and the aliphatic conjugated diene monomer units.

[Nitrile group-containing monomer unit]
Examples of nitrile group-containing monomers capable of forming nitrile group-containing monomer units 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. Examples include acrylonitrile; α-chloroacrylonitrile; 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 allowing the electrode mixture layer to adhere more firmly to the current collector.
Incidentally, the nitrile group-containing monomers can be used alone or in combination of two or more.

The ratio of the nitrile group-containing monomer unit contained in the polymer is preferably 20% by mass or more, and preferably 40% by mass or more, when the total repeating units of the polymer are 100% by mass. 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. If the proportion of the nitrile group-containing monomer unit in the polymer is 20% by mass or more, the electrode mixture layer can be adhered to the current collector more firmly, and the cycle characteristics of the electrochemical device can be further improved. can. In addition, the affinity of the polymer for organic solvents (especially polar organic solvents such as N-methylpyrrolidone) is ensured, and a binder composition in which the polymer is well dissolved in the organic solvent can be obtained. On the other hand, if the ratio of the nitrile group-containing monomer unit in the polymer is 85% by mass or less, the flexibility of the polymer can be ensured without excessively increasing the glass transition temperature. Therefore, an 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 aliphatic conjugated diene monomers. The aliphatic conjugated diene monomer capable of forming the aliphatic conjugated diene monomer unit is not particularly limited. aliphatic conjugated diene monomer) and 1,3-butadiene.

Examples of aliphatic conjugated diene monomers having 5 to 12 carbon atoms include 2-methyl-1,3-butadiene (isoprene, carbon atoms: 5), 2,3-dimethyl-1,3-butadiene (carbon number of atoms: 6), and among these, isoprene is preferred. When the polymer contains an aliphatic conjugated diene monomer unit having 5 to 12 carbon atoms derived from an aliphatic conjugated diene monomer having 5 to 12 carbon atoms, the flexibility of the polymer is ensured. be. In addition, it is presumed that the presence of a hydrophobic group (such as a methyl group) present on a carbon atom having a double bond improves the affinity of the polymer for blending components (especially carbon materials). , the ingredients can be better dispersed. A higher coating density can be achieved by coating the current collector with a slurry composition in which the ingredients are better dispersed. In addition, when forming an electrode mixture layer using a slurry composition containing a binder composition, each component is not unevenly distributed, and even when roll-pressing at a relatively low linear pressure, for example, While the density of the electrode mixture layer obtained is further increased, the electrode mixture layer can be adhered to the current collector more favorably. Therefore, it is possible to easily increase the density of the electrode mixture layer and achieve strong adhesion to the current collector at a higher level.
The aliphatic conjugated diene monomer having 5 to 12 carbon atoms may be used alone or in combination of two or more.

The proportion of aliphatic conjugated diene monomer units 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, preferably 50% by mass or less, and more preferably 25% by mass or less. If 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 compounding component (particularly, the carbon material) The affinity with is improved, and the coating density is further increased. Therefore, it is possible to easily increase the density of the electrode mixture layer and achieve strong adhesion to the current collector at a higher level. On the other hand, if 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, resulting in excessive softening of the polymer. is suppressed, the electrode mixture layer can be adhered well to the current collector.

In addition, if the polymer contains 1,3-butadiene units derived from 1,3-butadiene, the glass transition temperature is lowered and the flexibility of the polymer is sufficiently ensured. The material layer can be formed more easily.

The proportion of 1,3-butadiene units contained in the polymer is preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 7% by mass or more. It is preferably 25% by mass or less, even more preferably 15% by mass or less. If 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, if the proportion of 1,3-butadiene units in the polymer is 50% by mass or less, excessive softening of the polymer due to a significant decrease in the glass transition temperature is suppressed. can be adhered well to the current collector.

Here, from the viewpoint of easily increasing the density of the electrode mixture layer and achieving a higher level of strong adhesion to the current collector, the aliphatic conjugated diene monomer having 5 to 12 carbon atoms and 1,3-butadiene, and more preferably isoprene and 1,3-butadiene. That is, the polymer preferably contains both aliphatic conjugated diene monomer units having 5 to 12 carbon atoms and 1,3-butadiene units, and contains both isoprene units and 1,3-butadiene units. is more preferable.

In addition, the ratio of the aliphatic conjugated diene monomer units contained in the polymer (the total ratio of at least two aliphatic conjugated diene monomer units) is 100% by mass of the total repeating units of the polymer. , preferably 15% by mass or more, more preferably 20% by mass or more, still more 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 even more preferable. If the ratio of the aliphatic conjugated diene monomer units in the polymer is 15% by mass or more, the flexibility of the polymer can be ensured without excessively increasing the glass transition temperature. Therefore, an electrode mixture layer having a sufficiently high density can be easily formed. On the other hand, if the ratio of the aliphatic conjugated diene monomer unit in the polymer is 80% by mass or less, the electrode mixture layer is adhered to the current collector more firmly, thereby further improving the cycle characteristics of the electrochemical device. can be made

And the ratio of the amount of the aliphatic conjugated diene monomer unit to 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 preferably 20% by mass or more, preferably 80% by mass or less, more preferably 60% by mass or less, and even more preferably 40% by mass or less. If the ratio of the aliphatic conjugated diene monomer units in the total of the nitrile group-containing monomer units and the aliphatic conjugated diene monomer units is 15% by mass or more, a sufficiently densified electrode mixture layer can be formed. It can be easily formed, and if it is 80% by mass or less, excessive softening of the polymer due to a significant decrease in the glass transition temperature is suppressed, so that the electrode mixture layer can be well formed into a current collector. can be adhered. Further, if 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 electrolytic solution of the polymer The degree of swelling in the electrolyte (swelling degree of the electrolyte solution) is well controlled, and the polymer exhibits good binding properties in the electrolyte solution. Therefore, the cycle characteristics of the electrochemical device can be further improved.

In addition, the ratio of the proportion of aliphatic conjugated diene monomer units having 5 to 12 carbon atoms to the proportion of 1,3-butadiene units in the polymer is preferably 0.02 or more. It is more preferably 5 or more, more preferably 1 or more, particularly preferably greater than 1, preferably 50 or less, more preferably 10 or less, and 5 or less. More preferably, it is particularly preferably 4 or less. If 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 is 0.02 or more, the flexibility of the polymer is improved, and the blending component (Particularly, the affinity with the carbon material) is improved, and the coating density is increased. Therefore, it is possible to easily increase the density of the electrode mixture layer and achieve strong adhesion to the current collector at a higher level. On the other hand, if 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 greatly lowered. Since excessive softening of the polymer is suppressed, the electrode mixture layer can be adhered well 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 unit contained in the polymer is 0% by mass or more and 10% by mass or less from the viewpoint of easily increasing the density of the electrode mixture layer and achieving a high level of strong adhesion to the current collector. It is preferably 0% by mass or more and 5% by mass or less, and even more 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 monomers 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 units (repeating units) in the polymer.
The water-based 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 method is not particularly limited, and any method 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, and living radical polymerization can be used.
Commonly used emulsifiers, dispersants, polymerization initiators, polymerization aids, and the like can be used in the polymerization, and the amounts used are also generally used amounts.
The electrolyte 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 preferred. If the degree of swelling of the polymer in the electrolyte solution is 110% or more, the affinity of the polymer not only for the electrolyte solution but also for the organic solvent is ensured, and a binder composition in which the polymer is satisfactorily dissolved in the organic solvent can be obtained. . On the other hand, if the degree of swelling of the polymer in the electrolyte solution is 500% or less, the polymer can easily maintain the binding property in the electrolyte solution, and the electrochemical device can exhibit excellent characteristics (especially cycle characteristics). can.
Here, in the present invention, the "electrolytic solution swelling degree" can be measured using the method described in the examples of the present specification.

<Solvent>
The solvent that the binder composition may contain is not particularly limited, but an organic solvent is preferred. Examples of organic solvents 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-based polar organic solvents such as N,N-dimethylsulfoxide; aromatic hydrocarbons such as toluene, xylene, chlorobenzene, orthodichlorobenzene, and paradichlorobenzene; These may be used individually by 1 type, and may be used in mixture of 2 or more types. Among them, NMP is preferable as the solvent.

<Other ingredients>
In addition to the above components, the binder composition may contain components other than the predetermined polymer, such as a binder, a conductive material, a reinforcing material, a leveling agent, a viscosity modifier, and an electrolyte additive. may These are not particularly limited, and known ones such as those described in WO 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 by arbitrary ratios.

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

(Slurry composition for electrochemical element electrode)
The slurry composition for an electrochemical element electrode of the present invention is a slurry composition containing at least an electrode active material and the above-described binder composition for an electrochemical element electrode of the present invention. In other words, the slurry composition of the present invention usually comprises the electrode active material, the polymer described above, and the optionally blended other components described above dissolved and/or dispersed in the solvent described above. composition. Further, since the slurry composition of the present invention contains the above-described binder composition of the present invention, if the electrode mixture layer is formed using the slurry composition of the present invention, the electrode mixture layer can be easily made high. While increasing the density, it can be firmly adhered to the current collector.

<Electrode active material>
An electrode active material is a material that transfers electrons in an electrode of an electrochemical device. The slurry composition of the present invention preferably contains an electrode active material containing nickel (hereinafter sometimes abbreviated as "Ni-containing electrode active material") as an electrode active material. By using an electrode containing a Ni-containing electrode active material, the capacity of the electrochemical device can be further increased. Incidentally, the Ni-containing electrode active material can be particularly preferably used as a positive electrode active material in non-aqueous secondary batteries such as lithium ion secondary batteries.

<<Ni-containing electrode active material>>
Examples of the Ni-containing electrode active material include formula (A): Li(Ni _x Co _y M _(1-xy) )O ₂ [wherein 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. ] can be used.

Among those corresponding to the above formula (A), from the viewpoint of further increasing the capacity of the electrochemical device, the formula (A1): Li(Ni _x Co _y Al _(1-xy) )O ₂ [formula (A1 ), x and y satisfy the relational expressions of 0.30≦x≦1, 0≦y<0.7, and x+y≦1. ] is more preferable. In addition, among those corresponding to the above (A), from the viewpoint of improving the capacity and safety of the electrochemical device in a well-balanced manner, the formula (A2): Li(Ni _x Co _y Mn _(1-xy) )O ₂ [In formula (A2), x and y satisfy the relational expressions of 0.30≦x≦1, 0≦y<0.7, and x+y≦1. ] is more preferable.

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

As positive electrode active materials for lithium ion secondary batteries, in addition to the Ni-containing electrode active materials described above, lithium-containing cobalt oxide (LiCoO ₂ ), lithium manganate (LiMn ₂ O ₄ ), olivine-type lithium iron phosphate ( LiFePO ₄ ), olivine-type lithium manganese phosphate (LiMnPO ₄ ), and lithium-excess spinel compounds represented by Li _1+x Mn _2-x O ₄ (0<x<2).
The amount and particle size of the positive electrode active material are not particularly limited, and may be the same as those of conventionally used positive electrode active materials.

Examples of negative electrode active materials for lithium ion secondary batteries include carbon-based negative electrode active materials, metal-based negative electrode active materials, and negative electrode active materials in which these are combined.

Here, the carbon-based negative electrode active material refers to an active material having carbon as a main skeleton and capable of inserting lithium (also referred to as “doping”). Examples of carbon-based negative electrode active materials include carbonaceous materials and graphite quality materials.

Examples of the carbonaceous material include graphitizable carbon and non-graphitizable carbon having a structure close to an amorphous structure represented by glassy carbon.
Here, graphitizable carbon includes, for example, carbon materials made from tar pitch obtained from petroleum or coal. Specific examples include coke, mesocarbon microbeads (MCMB), mesophase pitch-based carbon fibers, and pyrolytic vapor growth carbon fibers.
Non-graphitic carbons include, for example, phenolic resin sintered bodies, polyacrylonitrile-based carbon fibers, pseudoisotropic carbons, furfuryl alcohol resin sintered bodies (PFA), and hard carbons.

Furthermore, examples of graphite materials include natural graphite and artificial graphite.
Here, as artificial graphite, for example, artificial graphite obtained by heat-treating carbon containing graphitizable carbon mainly at 2800 ° C. or higher, graphitized MCMB obtained by heat-treating MCMB at 2000 ° C. or higher, mesophase pitch-based carbon fiber at 2000 ° C. Graphitized mesophase pitch-based carbon fibers heat-treated as described above may be used.

In addition, the metal-based negative electrode active material is an active material containing a metal, and usually contains an element capable of intercalating lithium in its structure, and the theoretical electric capacity per unit mass when lithium is intercalated is 500 mAh / g or more. As the metal-based active material, for example, lithium metal, elemental metals 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 alloys thereof, as well as their oxides, sulfides, nitrides, silicides, carbides, phosphides, and the like. Among these, active materials containing silicon (silicon-based negative electrode active materials) are preferable as the metal-based negative electrode active materials. This is because the use of the silicon-based negative electrode active material can increase the capacity of the lithium ion secondary battery.

Silicon-based negative electrode active materials include, for example, silicon (Si), alloys containing silicon, SiO, SiO _x , and composites of Si-containing materials and conductive carbon obtained by coating or combining Si-containing materials with conductive carbon. etc. One of these silicon-based negative electrode active materials may be used alone, or two or more of them may be used in combination.
The amount and particle size of the negative electrode active material are not particularly limited, and can be the same as those of conventionally used negative electrode active materials.

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

Here, the content of the binder composition in the slurry composition for an electrochemical element electrode 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 more preferably 0 parts by mass or more, more preferably 1.5 parts by mass or more, and preferably 4.0 parts by mass or less, and 3.0 parts by mass. The amount is more preferably 2.5 parts by mass or less, more preferably 2.5 parts by mass or less. When the binder composition is added to 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 adhered to the current collector more firmly. On the other hand, if the binder composition is included 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 The capacity of the device can be sufficiently increased.

<Other ingredients>
Other components that can be blended in the slurry composition are not particularly limited, and include the same other components that can be blended in the binder composition described above. Moreover, other components may be used individually by 1 type, and may be used in combination of 2 or more types by arbitrary ratios.

<Preparation of slurry composition>
The slurry composition described above can be prepared by mixing the components described above. 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 film mix, the above components are optionally added. A slurry composition can be prepared by mixing with a solvent. As the solvent optionally added during preparation of the slurry composition, the same solvents as those described in the section of the binder composition can be used.

(electrode for electrochemical device)
The electrode for an electrochemical device of the present invention includes, for example, an electrode mixture layer formed on a current collector using the slurry composition for an electrochemical device electrode described above. Specifically, the electrode mixture layer is usually made of the dried slurry composition for the electrochemical element electrode described above, and the electrode mixture layer contains at least the electrode active material, the polymer described above, and optionally , and other ingredients. In addition, each component contained in the electrode mixture layer was contained in the slurry composition for the electrochemical element electrode, and the preferred abundance ratio of each component in the slurry composition is It is the same as the preferred abundance ratio of each component.
In the electrode for an electrochemical element of the present invention, the slurry composition for an electrochemical element electrode described above is used to form the electrode mixture layer. If produced, an electrochemical device having a high capacity and excellent cycle characteristics can be obtained.

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

<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 the coating method, a doctor blade method, a dip 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 side of the current collector, or may be applied to both sides. The thickness of the slurry film on the current collector after application and before drying can be appropriately set according to the desired thickness of the electrode mixture layer.

Here, as the current collector to which the slurry composition is applied, 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, one type of the above materials may be used alone, or two or more types may be used in combination at an arbitrary ratio.

<Drying process>
The method for drying the slurry composition on the current collector is not particularly limited, and known methods can be used. A drying method by irradiation can be mentioned. By drying the slurry composition on the current collector in this manner, the pre-pressing electrode mixture layer can be formed on the current collector.

<Press process>
The linear pressure when roll-pressing the pre-pressed electrode mixture layer on the current collector is required 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 are preferable. Since the pre-pressed electrode mixture layer on the current collector is formed from the slurry composition of the present invention, it can be easily compressed at a linear pressure of 500 kN/cm or more to form a high-density pressed electrode mixture. You can get layers. Moreover, if the linear pressure is 3000 kN/cm or less, the electrode active material is not excessively destroyed by pressing.
In addition, the roll temperature at the time of roll pressing is usually 25° C. or more and 150° C. or less. Further, the conveying speed of the electrode mixture layer before pressing and the laminate of current collectors during roll pressing is usually 5 m/min or more and 100 m/min or less. The number of times of roll pressing may be plural times, but is usually one time.

(Electrochemical element)
The electrochemical device of the present invention is not particularly limited, and may be 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, the case where the electrochemical device 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 element of the present invention usually comprises electrodes (a positive electrode and a negative electrode), an electrolytic solution, and a separator, and uses the electrode for an electrochemical element of the present invention as at least one of the positive electrode and the negative electrode. .

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

<Electrolyte>
As the electrolytic solution, an organic electrolytic solution in which a supporting electrolyte is dissolved in an organic solvent is usually used. Lithium salts, for example, are used as supporting electrolytes for lithium ion secondary batteries. Examples of lithium salts 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 they are easily dissolved in a solvent and exhibit a high degree of dissociation. In addition, one electrolyte may be used alone, or two or more electrolytes may be used in combination at an arbitrary ratio. Generally, lithium ion conductivity tends to increase as a supporting electrolyte with a higher degree of dissociation is used, so the lithium ion conductivity can be adjusted depending on the type of supporting electrolyte.

The organic solvent used in the electrolytic solution is not particularly limited as long as it can dissolve the supporting electrolyte. Examples include dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), carbonates such as butylene carbonate (BC) and ethyl methyl 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 dimethylsulfoxide and the like are preferably used. A mixture of these solvents may also be used. Among them, carbonates are preferably used because they have a high dielectric constant and a wide stable potential range, and a mixture of ethylene carbonate and ethyl methyl carbonate is more preferably used.
Further, known additives such as vinylene carbonate (VC), fluoroethylene carbonate (FEC), and ethyl methyl sulfone may be added to the electrolytic solution.

<Separator>
The separator is not particularly limited, and for example, those described in JP-A-2012-204303 can be used. Among these, the film thickness of the entire separator can be made thin, and as a result, the ratio of the electrode active material in the lithium ion secondary battery can be increased to increase the capacity per volume. Microporous membranes made of resins of the system (polyethylene, polypropylene, polybutene, polyvinyl chloride) are preferred.

<Method for manufacturing lithium ion secondary battery>
A lithium-ion secondary battery as an electrochemical device of the present invention can be prepared, for example, by superimposing a positive electrode and a negative electrode with a separator interposed therebetween, and winding or folding this according to the shape of the battery as necessary to form a battery container. It can be produced by putting it in a battery container, injecting an electrolytic solution into the battery container, and sealing the battery container. In order to prevent the internal pressure rise of the lithium ion secondary battery and the occurrence of overcharge/discharge, etc., a fuse, an overcurrent prevention element such as a PTC element, an expanded metal, a lead plate, etc. may be provided as necessary. . The shape of the lithium-ion secondary battery may be, for example, coin-shaped, button-shaped, sheet-shaped, cylindrical, rectangular, or flat.

EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited to these examples. In the following description, "%" and "parts" representing amounts are based on mass unless otherwise specified.
In the examples and comparative examples, the degree of swelling of the electrolyte solution 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 the lithium ion The cycle characteristics of secondary batteries were evaluated by the following methods. All evaluation results are shown in Table 1.

<Polymer electrolyte swelling degree>
The positive electrode binder composition (NMP solution of the polymer) is applied to a polytetrafluoroethylene sheet, dried at a temperature of 80 to 120° C. for 0.5 to 3 hours, and cast to a thickness of 500 μm ± 50 μm. got the film. This cast film was cut into a square of 1 cm×1 cm to obtain a test piece, and the mass of the test piece (mass A before immersion) was measured. After that, 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 (by weight) to a concentration of 5% by mass, and then adding LiPF ₆ to the mixture after adding FEC to a concentration of 1.0M. and vinylene carbonate was added to the mixture after dissolving LiPF ₆ so as to have a concentration of 2% by mass. After the immersed test piece was pulled up, the electrolytic solution on the surface was wiped off with towel paper, and then the mass of the test piece (mass after immersion B) was measured.
Then, the degree of swelling of the electrolytic solution (%) was calculated using the following formula. A polymer with a lower degree of swelling in an electrolyte solution is more likely to retain its binding properties in the electrolyte solution, and can exhibit excellent characteristics (especially cycle characteristics) in the electrochemical device.
Swelling degree of electrolytic solution (%) = Mass after immersion B/Mass before immersion A x 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, which was fixed on a horizontal table with the positive electrode mixture layer facing up. Then, after a 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 off from one end of the test piece in a 180° direction at a rate of 50 mm/min. At this time, the cellophane tape specified in JIS Z1522 was used. The measurement was performed 10 times, and the average value of the obtained values was taken as the peel strength (N/m), which was evaluated according to the following criteria. A higher peel strength indicates that the positive electrode mixture layer is firmly adhered to the current collector.
A: Peel strength of 70 N/m or more B: Peel strength of 50 N/m or more and less than 70 N/m C: Peel strength of 30 N/m or more and less than 50 N/m D: Peel strength of 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 (coating density)>
The coating density (g/cm ³ ) was calculated from the thickness (cm) and coating amount (g/cm ² ) of the positive electrode mixture layer before pressing of the positive electrode material 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 mixture layer before pressing), the easier it is to form a high-density positive electrode mixture layer by roll pressing.
Coating density (g/cm ³ ) = coating amount (g/cm ² )/thickness (cm)
A: Application density is 2.5 g/cm ³ or more B: Application density is 2.4 g/cm ³ or more and less than 2.5 g/cm ³ C: Application density is 2.3 g/cm ³ or more and less than 2.4 g/cm ³ D: Coating density less than 2.3 g/cm ³ <density of positive electrode after pressing (press density)>
A circular test piece having a diameter of 1.2 cm was punched from the positive electrode material. This test piece was placed on a flat plate and pressed at a pressure of 9 MPa (press test). Then, the thickness (cm) and weight (g) of the positive electrode mixture layer after pressing were determined, 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 mixture 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. The higher the press density, the better the compressibility of the positive electrode mixture layer before pressing, indicating that the positive electrode mixture layer with high density 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 and less than 3.8 g/cm ³ C: Press density is 3.6 g/cm ³ or more and less than 3.7 g/cm ³ D: Press density of 3.5 g/cm ³ or more and less than 3.6 g/cm ³ E: Press density of less than 3.5 g/cm ³ <Cycle characteristics of lithium ion secondary battery>
The obtained lithium ion secondary battery was aged for 10 hours at a state of charge (SOC) of 10% at 60°C. After aging, the operation of charging at 0.2C until the voltage reached 4.2V and discharging at 0.2C until the voltage reached 3.0V was repeated three times. After that, the lithium ion secondary battery was charged at 1 C to a voltage of 4.2 V and discharged at 1 C to a voltage of 3.0 V in an environment of 45° C., and this operation 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)} x 100) and evaluated according to the following criteria. A higher capacity retention rate indicates better cycle characteristics.
A: Capacity retention rate of 84% or more B: Capacity retention rate of 82% or more and less than 84% C: Capacity retention rate of 80% or more and less than 82% D: Capacity retention rate of 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 aliphatic conjugated diene monomers, 70.0 parts of acrylonitrile as nitrile group-containing monomers, and 0.4 parts of t-dodecyl mercaptan 132 parts of ion-exchanged water, 3 parts of sodium dodecylbenzenesulfonate, 0.5 parts of β-naphthalenesulfonic acid formalin condensate sodium salt, 0.3 parts of potassium persulfate, and 0.05 parts of ethylenediaminetetraacetic acid sodium salt was charged, and the polymerization was carried out while maintaining the polymerization temperature at 15° C. until the polymerization conversion reached 94%. After that, the content was returned to normal temperature, the inside of the system was made into a nitrogen atmosphere, and then concentrated using an evaporator until the solid content concentration reached 40% to obtain an aqueous polymer dispersion.
320 parts of NMP was added to 100 parts of the water dispersion of the polymer, and then the water was evaporated under reduced pressure to replace the solvent, thereby obtaining an NMP solution of the polymer (positive electrode binder composition).
After 100 g of NMP solution of the obtained polymer was coagulated with 1 L of methanol, it was vacuum-dried at 60° C. overnight to obtain a dried product. This dried product was analyzed by the NMR method, and it was confirmed that the polymer contained 70% acrylonitrile units, 10% 1,3-butadiene units, and 20% isoprene units.
<Preparation of positive electrode slurry composition>
96 parts of Li(Ni _0.5 Co _0.2 Mn _0.3 )O ₂ (average particle diameter: 10 μm) as a positive electrode active material, and acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd., product name “HS -100"), 2.0 parts of the positive electrode binder composition described above (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, the slurry composition for positive electrodes was prepared by mixing with the said mixer.
<Preparation 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 an 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 then at 120° C. for 20 minutes, and then heat-treated at 150° C. for 2 hours to obtain a positive electrode material roll consisting of a negative electrode mixture layer before pressing and a current collector. rice field. This positive electrode material was roll-pressed at a linear pressure of 2000 kN/cm to produce a positive electrode having a positive electrode mixture layer with a density of 3.7 g/cm ³ on one side of a 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 thickener, and an appropriate amount of water were stirred in a planetary mixer to prepare a negative electrode slurry composition.
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 a 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 at 110° C. for 20 minutes, and then heat-treated at 150° C. for 2 hours to obtain a negative electrode blank. This negative electrode material was rolled by a roll press to prepare a negative electrode having a negative electrode mixture layer with a density of 1.8 g/cm ³ on one side of a current collector.
<Production of lithium ion secondary battery>
The prepared 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 mixture layer and the negative electrode mixture layer faced each other with the separator interposed therebetween. Then, the obtained wound body was compressed in 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 (based on weight) so as to have a concentration of 5% by mass. Then, LiPF ₆ was dissolved in the mixture after the addition of FEC to a concentration of 1.0M. Then, an electrolytic solution was prepared by adding vinylene carbonate to the mixture after dissolving LiPF ₆ so that the concentration was 2% by mass.
Then, the wound body after compression was placed in an aluminum laminate case together with 3.2 g of electrolyte. Then, a lead wire was connected to a predetermined portion of the negative electrode and a lead wire was connected to a predetermined portion 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-shaped battery 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 2-7)
In the same manner as in Example 1, except that the monomer composition shown in Table 1 was used when preparing the polymer, NMP solution of the polymer (binder composition for positive electrode), slurry composition for positive electrode, positive electrode, negative electrode , and a lithium-ion secondary battery were produced. Analysis by the NMR method was performed in the same manner as in Example 1, and the ratio of a certain monomer unit in the polymer to the total monomers used in the polymerization of the polymer was It was confirmed that it matches the ratio of (feed ratio).

(Comparative Examples 1 and 2)
In the same manner as in Example 1, except that the monomer composition shown in Table 1 was used when preparing the polymer, NMP solution of the polymer (binder composition for positive electrode), slurry composition for positive electrode, positive electrode, negative electrode , and a lithium-ion secondary battery were fabricated. Analysis by the NMR method was performed in the same manner as in Example 1, and the ratio of a certain monomer unit in the polymer to the total monomers used in the polymerization of the polymer was It was confirmed that it matches the ratio of (feed ratio).

(Comparative Example 3)
An aqueous polymer dispersion was prepared in the same manner as in Example 1, except that the monomer composition shown in Table 1 was used during the preparation of the polymer. Then, the solvent was replaced with NMP 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 by using such a positive electrode binder composition, a positive electrode, a negative electrode, and a lithium ion secondary battery were not produced. . In addition, the item of the electrolyte solution swelling degree of the polymer was evaluated. Further, analysis by the NMR method was performed in the same manner as in Example 1, and the ratio of a certain monomer unit in the polymer to the total monomers used in the polymerization of the polymer was It was confirmed that it matches the ratio of (feed 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 types of aliphatic conjugated diene monomer units, while increasing the coating density , the electrode mixture layer can be sufficiently densified. In addition, in Examples 1 to 7, it can be seen that the electrode mixture layer is firmly adhered to the current collector, and sufficiently excellent cycle characteristics can be exhibited in the lithium ion secondary battery.
On the other hand, in Comparative Example 1 using a binder composition containing a polymer containing only a 1,3-butadiene unit as an aliphatic conjugated diene monomer unit, although the nitrile group-containing monomer unit was used, the electrode mixture It can be seen that densification of the layer is difficult.
In addition, in Comparative Example 2 using a binder composition containing a polymer containing only isoprene units as aliphatic conjugated diene monomer units although it contains nitrile group-containing monomer units, the high density of the electrode mixture layer It can be seen that it is difficult to
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 Since it did not dissolve in NMP, a positive electrode, a negative electrode, and a lithium ion secondary battery were not produced.

According to the present invention, a binder composition for an electrochemical element electrode and a slurry composition for an electrochemical element electrode, which can easily increase the density of the electrode mixture layer and firmly adhere the electrode mixture layer to the current collector. can be provided.
Further, according to the present invention, there is provided an electrode for an electrochemical element which can increase the capacity of the electrochemical element and which can exhibit excellent cycle characteristics in the electrochemical element, and a method for producing the electrode for the electrochemical element. can be done.
Furthermore, according to the present invention, it is possible to provide an electrochemical device that has a high capacity and excellent cycle characteristics.

Claims (10)

A binder composition for an electrochemical element electrode containing a polymer,
the polymer comprises a nitrile group-containing monomer unit and at least two aliphatic conjugated diene monomer units ;
The aliphatic conjugated diene monomer unit contains an aliphatic conjugated diene monomer unit having 5 to 12 carbon atoms and a 1,3-butadiene unit, and the 1,3-butadiene unit in the polymer A binder composition for an electrochemical element electrode, wherein the ratio of the proportion of the aliphatic conjugated diene monomer unit having 5 to 12 carbon atoms to the proportion is greater than 1 . 2. The binder composition for an electrochemical element electrode according to claim 1 , wherein the proportion of said aliphatic conjugated diene monomer unit having 5 to 12 carbon atoms in said polymer is 1 to 50 mass %. thing. 3. The binder composition for an electrochemical element electrode according to claim 1 , wherein the proportion of said 1,3-butadiene unit in said polymer is 1% by mass or more and 50% by mass or less. 4. The binder composition for an electrochemical element electrode according to claim 1 , wherein the proportion of said nitrile group-containing monomer unit in said polymer is 20% by mass or more and 85% by mass or less. Claims 1 to 4 , wherein 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 more than 1 to 50. The binder composition for an electrochemical element electrode according to any one of the above. A slurry composition for an electrochemical element electrode, comprising an electrode active material and the binder composition for an electrochemical element electrode according to any one of claims 1 to 5 . 7. The slurry composition for an electrochemical element electrode according to claim 6 , wherein said electrode active material is an electrode active material containing nickel. An electrode for an electrochemical element, comprising an electrode mixture layer formed using the slurry composition for an electrochemical element electrode according to claim 6 or 7 . An electrochemical device comprising the electrode for an electrochemical device according to claim 8 . A step of applying the slurry composition for an electrochemical element electrode according to claim 6 or 7 onto a current collector;
a step of drying the electrochemical element electrode slurry composition applied on the current collector to form a pre-pressing electrode mixture layer on the current collector;
a step of roll-pressing the pre-pressed electrode mixture layer at a linear pressure of 500 kN/cm or more and 3000 kN/cm or less to obtain a post-press electrode mixture layer;
A method for manufacturing an electrode for an electrochemical device.