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 spinel-type lithium titanium complex oxide, wherein:

the lithium anium complex oxide includes lithium, titanium, manganese, boron and oxygen, and

the lithium titanium complex oxide includes manganese in an amount of more than 0 moles and 0.3 moles or less and boron in an amount of more than 0 moles and 0.3 moles or less, to 5 moles of elements included in the lithium titanium complex oxide other than lithium and oxygen.

2. The negative electrode active material for a lithium ion secondary battery according to claim 1 , wherein the lithium titanium complex oxide has a composition expressed as Li 4 Ti 5-x-z Mn x B z O 12 , where 0<x≦0.3 and 0<z≦0.3.

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

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

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

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 Mn sources selected from MnO 2 and MnCO 3 , and one or more additive materials selected from B 2 O 3 , H 3 BO 3 and V 2 O 5 to make a mixture including at least lithium, titanium and manganese; and

calcining the mixture at a temperature of 700° C. or more and 1000° C. or less so as to obtain so as to obtain a lithium titanium complex oxide including at least lithium, titanium and manganese, wherein:

the mixture further includes boron, and

the mixture has mole ratios of Li:Ti:Mn:B=4:(5−x−z):x:z, where 0<x≦0.3, and 0<z≦0.3.