METHOD FOR PRODUCING NEGATIVE ELECTRODE FOR LITHIUM ION SECONDARY BATTERIES

1 . A method for producing a negative electrode for a lithium ion secondary battery, the negative electrode comprising a current collector, and a negative electrode active material layer disposed on the current collector, the method comprising:

preparing a slurry comprising a negative electrode active material, a binder, a water-soluble polymeric thickener, and an aqueous solvent; and

forming a coating layer to be used as the negative electrode active material layer by applying the slurry on the current collector and drying the slurry for removing the aqueous solvent,

wherein said preparing the slurry comprises:

preparing a dispersion comprising the water-soluble polymeric thickener dissolved in the aqueous solvent and an acrylic binder dispersed as the binder; and

preparing and stirring a mixture comprising a powder material comprising the negative electrode active material, and the dispersion.

2 . The method for producing a negative electrode for a lithium ion secondary battery, according to claim 1 ,

wherein said preparing the slurry comprises:

preparing a first dispersion comprising an acrylic binder dispersed in the aqueous solvent;

preparing, by adding the water-soluble polymeric thickener to the first dispersion, a second dispersion comprising the water-soluble polymeric thickener dissolved; and

preparing and stirring a mixture comprising a powder material comprising the negative electrode active material, and the second dispersion.

3 . The production method according to claim 1 ,

wherein said preparing and stirring the mixture comprises:

stirring the mixture having a solid concentration of 50% by mass or higher and 70% by mass or lower; and

stirring the mixture with the solid concentration lowered to 40% by mass or higher and lower than 50% by mass.

4 . The production method according to claim 1 , wherein an amount of the acrylic binder to be added is 0.5 to 5% by mass with respect to the aqueous solvent.

5 . The production method according to claim 1 , wherein an amount of the water-soluble polymeric thickener to be added is 0.5 to 5% by mass with respect to the aqueous solvent.

6 . The production method according to claim 1 , wherein the water-soluble polymeric thickener comprises carboxymethyl cellulose.

7 . The production method according to claim 6 , wherein the carboxymethyl cellulose is a sodium salt.

8 . The production method according to claim 1 , wherein the negative electrode active material is a carbonaceous material.

9 . The production method according to claim 8 , wherein the carbonaceous material is a graphite-based material.

10 . The production method according to claim 1 , wherein the negative electrode active material has an average particle diameter of 2 to 40 μm.

11 . The production method according to claim 1 , wherein the powder material contains a conductive auxiliary agent.

12 . The production method according to claim 11 , wherein the conductive auxiliary agent is a carbonaceous material.