Method for producing rectangular flat secondary battery

1. A method for producing a rectangular flat secondary battery, the method comprising the steps of:

a) spirally winding a positive electrode plate and a negative electrode plate with a separator interposed therebetween, thereby forming an electrode group having a circular shape or an oval shape;

b) inserting a center core member for applying a pressure to the electrode group in a winding core hole of the electrode group;

c) compressing the electrode group to deform the electrode group into a rectangular substantially flat shape;

d) accommodating the electrode group in a rectangular flat armoring can with a base; and

e) sealing an opening portion of the armoring can.

2. The method of claim 1 , characterized in that a negative electrode substance formed on the negative electrode plate is made of a compound containing at least one of Si and Sn.

3. The method of claim 1 , characterized in that the center core member is made of an elastic body having a plate shape and a Young's modulus of 2.0×10 −3 GPa or more.

4. The method of claim 3 , characterized in that the plate-shape elastic body is formed so as to have a wedge shape.

5. The method of claim 3 , characterized in that the plate-shape elastic body is made of a material which absorbs an electrolyte and swells.

6. The method of claim 5 , characterized in that the material which absorbs an electrolyte and swells includes polyvinylidene fluoride, styrene-butadiene copolymer, or acrylonitrile butadiene styrene copolymer.

7. The method of claim 1 , characterized in that the center core member is made of an elastic body formed so as to have a C-shape.

8. The method of claim 1 , characterized in that the center core member is made of a member including a spring for applying a pressure to the electrode group.