Binder, cathode mixture and anode mixture
A binder, including a fluoropolymer, the fluoropolymer including a polymerization unit based on vinylidene fluoride and a polymerization unit based on a monomer having an amide group represented by —CO—NRR′ (R and R′ are the same as or different from each other and each represent a hydrogen atom or an alkyl group optionally having a substituent group) or an amide bond represented by —CO—NR″— (R″ represents a hydrogen atom, an alkyl group optionally having a substituent group, or a phenyl group optionally having a substituent group) and having a solution viscosity of 10 to 20,000 mPa·s. Also disclosed is a positive electrode mixture and a negative electrode mixture containing the binder, a positive electrode, a negative electrode and a lithium ion secondary cell.
1. A binder, comprising a fluoropolymer,
the fluoropolymer including a polymerization unit based on vinylidene fluoride, a polymerization unit based on tetrafluoroethylene, and a polymerization unit based on a monomer having an amide group represented by —CO—NRR′ (R and R′ are the same as or different from each other and each represent a hydrogen atom or an alkyl group optionally having a substituent group) or an amide bond represented by —CO—NR″— (R″ represents a hydrogen atom, an alkyl group optionally having a substituent group, or a phenyl group optionally having a substituent group) and having a solution viscosity of 10 to 20,000 mPa·s,
wherein the fluoropolymer includes the polymerization unit based on vinylidene fluoride in an amount of 50 to 90 mol %, the polymerization unit based on tetrafluoroethylene in an amount of 9.9 to 49.9 mol %, and the polymerization unit based on a monomer having an amide group or an amide bond in an amount of 0.01 to 2 mol % relative to the amount of all the polymerization units.
2. The binder according to claim 1 ,
wherein the fluoropolymer includes a polymerization unit based on at least one monomer selected from the group consisting of vinyl fluoride, trifluoroethylene, trifluorochloroethylene, fluoroalkyl vinyl ether, hexafluoropropylene, 2,3,3,3-tetrafluoropropene, and propylene.
3. The binder according to claim 1 ,
wherein the fluoropolymer has a weight average molecular weight of 50000 to 2000000.
4. The binder according to claim 1 , further comprising a vinylidene fluoride (VdF) polymer,
wherein the fluoropolymer and the VdF polymer have a mass ratio [(fluoropolymer)/(VdF polymer)] of 90/10 to 10/90.
5. The binder according to claim 4 ,
wherein the VdF polymer has a weight average molecular weight of 50000 to 2000000.
6. A positive electrode mixture comprising a positive electrode active material, an organic solvent, and the binder according to claim 1 .
7. A negative electrode mixture comprising a negative electrode active material, an organic solvent, and the binder according to claim 1 .
8. A positive electrode comprising a positive electrode current collector and a positive electrode active material layer formed of a positive electrode active material and the binder according to claim 1 on the positive electrode current collector.
9. A negative electrode comprising a negative electrode current collector and a negative electrode active material layer formed of a negative electrode active material and the binder according to claim 1 on the negative electrode current collector.
10. A lithium ion secondary cell comprising the positive electrode according to claim 8 , a negative electrode, and a nonaqueous electrolyte.
11. A lithium ion secondary cell comprising a positive electrode, the negative electrode according to claim 9 , and a nonaqueous electrolyte.