Method of manufacturing lithium-ion secondary battery positive electrode, method of manufacturing lithium-ion secondary battery, lithium-ion secondary battery positive electrode, and lithium-ion secondary battery

Abstract

A method of manufacturing a lithium-ion secondary battery positive electrode comprises a coating material preparing step of preparing a positive electrode active material layer forming coating material by mixing a positive electrode active material, a binder, a conductive auxiliary, an organic solvent, and water; and an active material layer forming step of forming a positive electrode active material layer on a current collector by using the positive electrode active material layer forming coating material. The binder is polyvinylidene fluoride produced by emulsion polymerization. The positive electrode active material layer forming coating material is prepared in the coating material preparing step such that the amount of water added (% by mass) based on the total amount of the organic solvent and water and the pH of the positive electrode active material satisfy the following expression (1): 48≦[the amount of water added+(4.25×the pH of the positive electrode active material)]≦52  (1)

1 . A method of manufacturing a lithium-ion secondary battery positive electrode, the method comprising:
 a coating material preparing step of preparing a positive electrode active material layer forming coating material by mixing at least a positive electrode active material, a binder, a conductive auxiliary, an organic solvent, and water; and   an active material layer forming step of forming a positive electrode active material layer on a current collector by using the positive electrode active material layer forming coating material;   wherein the binder is polyvinylidene fluoride produced by emulsion polymerization; and   wherein the positive electrode active material layer forming coating material is prepared in the coating material preparing step such that the amount of water added (% by mass) based on the total amount of the organic solvent and water and the pH of the positive electrode active material satisfy the following expression (1):
   48≦[the amount of water added+(4.25×the pH of the positive electrode active material)]≦52  (1) 
   
   
   
       2 . A method of manufacturing a lithium-ion secondary battery positive electrode according to  claim 1 , wherein the amount of water added in the coating material preparing step is 4 to 10% by mass based on the total amount of the organic solvent and water. 
   
   
       3 . A method of manufacturing a lithium-ion secondary battery positive electrode according to  claim 1 , wherein the organic solvent is N-methyl-2-pyrrolidone. 
   
   
       4 . A method of manufacturing a lithium-ion secondary battery having a step of making a positive electrode by the method of manufacturing a lithium-ion secondary battery positive electrode according to  claim 1 . 
   
   
       5 . A lithium-ion secondary battery positive electrode comprising a current collector and a positive electrode active material layer formed on the current collector;
 wherein the positive electrode active material layer contains a positive electrode active material, a binder, and a conductive auxiliary;   wherein the binder is polyvinylidene fluoride produced by emulsion polymerization; and   wherein at least a part of a surface of the positive electrode active material in the positive electrode active material layer is covered with a coating layer formed by dispersing the conductive auxiliary into the binder.   
   
   
       6 . A lithium-ion secondary battery positive electrode according to  claim 5 , wherein a plurality of pieces of the positive electrode active material are connected to each other through the coating layer in the positive electrode active material layer. 
   
   
       7 . A lithium-ion secondary battery positive electrode made by the method of manufacturing a lithium-ion secondary battery positive electrode according to  claim 1 . 
   
   
       8 . A lithium-ion secondary battery comprising the lithium-ion secondary battery positive electrode according to  claim 5 . 
   
   
       9 . A lithium-ion secondary battery comprising the lithium-ion secondary battery positive electrode according to  claim 7 .