Patent ID: 7862930

Claim:
A negative electrode for a lithium ion secondary battery, including a current collector and an active material layer carried on said current collector: wherein said active material layer comprises a deposit including silicon and an element M incapable of forming an alloy with lithium; a proportion of said element M in the thickness direction of said active material layer is larger in a first side contacting said current collector than in a second side opposite to said first side; said element M is titanium, said active material layer comprises an amorphous alloy including silicon and said element M, and the negative electrode satisfies the relation formula (1): T/ 100 â‰¦T 1 T/ 3 where T is a thickness of said active material layer, T 1 is a thickness of the SiM X portion in the range of 0.3â‰¦x in said active material layer, and in the remainder of said active material layer not in the region where the SiM x portion is in the range of 0.3â‰¦x, the amorphous alloy SiM x meets the limitation of 0<xâ‰¦0.2.