Copolymer, composition, slurry for positive electrode, positive electrode, and secondary battery

Abstract

To provide a copolymer that can form slurry having dispersoids such as a conduction aid highly dispersed therein, a composition, a slurry for positive electrodes, a positive electrode, and a secondary battery.SOLUTION: A copolymer comprises a polyvinyl alcohol structure and a first monomer unit, wherein the first monomer unit is at least one of a methacrylonitrile monomer unit and a methacrylic acid monomer unit, the copolymer having a molecular weight distribution of 2.6 or less.SELECTED DRAWING: Figure 1

Claims

1. A copolymer comprising a polyvinyl alcohol structure and a first monomer unit, The first monomer unit is at least one of (meth)acrylonitrile monomer units and (meth)acrylic acid monomer units. A copolymer having a molecular weight distribution of 2.6 or less and a number-average molecular weight of 10,000 or more.

2. The copolymer according to claim 1, wherein the first monomer unit comprises at least (meth)acrylonitrile monomer units.

3. The copolymer according to claim 1 or claim 2, wherein the copolymer contains 0.1 to 80% by mass of a polyvinyl alcohol structure when the copolymer is 100% by mass.

4. The copolymer according to any one of claims 1 to 3, comprising polymer block A containing a polyvinyl alcohol structure and polymer block B containing the first monomer unit.

5. The copolymer according to claim 4, wherein the number-average molecular weight of the polymer block A is 1,000 to 500,000.

6. The copolymer according to claim 4 or 5, wherein the molecular weight distribution of the polymer block A is 2.5 or less.

7. A copolymer according to any one of claims 1 to 6, having a structure derived from a RAFT agent.

8. The copolymer according to any one of claims 1 to 7, wherein the transition metal content is 500 ppm or less.

9. The copolymer according to any one of claims 1 to 7, wherein the total content of the thioether structure, disulfide structure, and sulfone structure is 3% by mass or less.

10. A dispersion consisting of 2% by mass of the copolymer, 4% by mass of carbon black, and 94% by mass of N-methylpyrrolidone, with a shear rate of 1S at 25°C. －１ and 10S －１ The steady flow viscosity measured by η Ｘ１ , and η Ｘ１０ Let mPa·S be used. The complex viscosity of the dispersion, measured at 25°C at angular frequencies of 1 rad / s and 10 rad / s, is given by η Ｙ１ and η Ｙ１０ When expressed as mPa·S, η Ｙ１ / η Ｘ１ 、η Ｙ１０ / η Ｘ１０ is 0.6 to 1.9, respectively, the copolymer according to any one of claims 1 to 9.

11. A composition comprising a copolymer, a conductive additive, and a dispersion medium, The copolymer is a copolymer comprising a polyvinyl alcohol structure and a first monomer unit, The first monomer unit is at least one of (meth)acrylonitrile monomer units and (meth)acrylic acid monomer units. A composition in which the molecular weight distribution of the copolymer is 2.6 or less.

12. A slurry for a positive electrode, comprising the composition according to claim 11 and a positive electrode active material.

13. The cathode slurry according to claim 12, wherein the copolymer content is 0.02 to 2.00% by mass when the total amount of solids in the cathode slurry is 100% by mass.

14. A positive electrode comprising a metal foil and a coating film of the positive electrode slurry according to claim 12 or 13 formed on the metal foil.

15. A secondary battery comprising the positive electrode described in claim 14, wherein the secondary battery is one or more selected from the group consisting of a lithium-ion secondary battery, a sodium-ion secondary battery, a magnesium-ion secondary battery, or a potassium-ion secondary battery.

16. The positive electrode active material is LiNi Ｘ Mn （２－Ｘ） O ４ (However, 0 < X ​​< 2), Li(Co Ｘ Ni Ｙ Mn Ｚ ) O ２ (wherein 0 < X ​​< 1, 0 < Y < 1, 0 < Z < 1, and X + Y + Z = 1), and Li(Ni Ｘ Co Ｙ Al Ｚ ) O ２ The secondary battery according to claim 15, wherein it includes at least one selected from 0 < X ​​< 1, 0 < Y < 1, 0 < Z < 1, and X + Y + Z = 1.

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