NEGATIVE ELECTRODE ACTIVE MATERIAL FOR LITHIUM ION SECONDARY BATTERY AND METHOD FOR PRODUCING THE SAME

1 . A negative electrode active material for a lithium ion secondary battery, containing a lithium titanium complex oxide having a composition expressed as Li 4 Ti 5-x-y Fe x V y O 12 (where 0<x≦0.3, 0<y≦0.05).

2 . A negative electrode active material for a lithium ion secondary battery, containing a lithium titanium complex oxide having a composition expressed as Li 4 Ti 5-x-z Fe x B z O 12 (where 0<x≦0.3, 0<z≦0.3).

3 . The negative electrode active material for a lithium ion secondary battery according to claim 1 , wherein an average particle size of primary particles of the lithium titanium complex oxide is 1 μm or more and 5 μm or less.

4 . The negative electrode active material for a lithium ion secondary battery according to claim 2 , wherein an average particle size of primary particles of the lithium titanium complex oxide is 1 μm or more and 11 μm or less.

5 . The negative electrode active material for a lithium ion secondary battery according to claim 1 , wherein x satisfies 0<x≦0.1.

6 . The negative electrode active material for a lithium ion secondary battery according to claim 2 , wherein x satisfies 0<x≦0.1.

7 . The negative electrode active material for a lithium ion secondary battery according to claim 3 , wherein x satisfies 0<x≦0.1.

8 . The negative electrode active material for a lithium ion secondary battery according to claim 4 , wherein x satisfies 0<x≦0.1.

9 . A method for producing a negative electrode active material for a lithium ion secondary battery, comprising the steps of:

uniformly mixing together a lithium source selected from LiOH, LiOH hydrates and Li 2 CO 3 , a titanium oxide having an anatase crystalline structure, one or more Fe source selected from Fe 2 O 3 and FeOOH, and one or more additive material selected from B 2 O 3 , H 3 BO 3 and V 2 O 5 ; and

calcining the mixture at a temperature of 700° C. or more and 1000° C. or less.