LITHIUM ION SECONDARY BATTERY

摘要

Disclosed is a lithium ion secondary battery comprising an electrode plate group for lithium ion secondary batteries. The electrode plate group is obtained by winding or stacking a negative electrode plate (406), a positive electrode plate (407) and a separator (403). The negative electrode plate (406) has such a structure wherein a negative electrode mix layer (404) is formed on both sides of a sheet-like negative electrode collector (401) mainly containing copper, and the positive electrode plate (407) has such a structure wherein a positive electrode mix layer (405) is formed on both sides of a sheet-like positive electrode collector (402) mainly containing aluminum. The separator (403) holds an electrolyte solution. In this lithium ion secondary battery, the thickness of the positive electrode collector (402) is smaller than that of the negative electrode collector (401). Consequently, the safety of the battery by itself against physical impact from inside or outside the battery can be secured without sacrificing fundamental performances required for high output batteries.