LITHIUM SECONDARY BATTERY, AND NEGATIVE ACTIVE MATERIAL FOR THE LITHIUM SECONDARY BATTERY

摘要

PROBLEM TO BE SOLVED: To provide a lithium secondary battery having high initial efficiency and a cycle characteristic, and a negative active material used for it. SOLUTION: A negative active material comprising powder of a silicon material containing boron and having 0.1-50 wt.% of boron content in the silicon material is used as a negative active material, in a lithium secondary battery containing a positive active material, the negative active material and a nonaqueous electrolyte. A 50%-cumulative size of the negative active material powder is 1-100 μm, and a peak intensity ratio (SiB4;021)/I(Si;111) of peak intensity of a diffracted ray from a (021) plane of SiB4 to peak intensity of diffracted ray from a (111) plane of Si in an X-ray wide angle diffraction method for the negative active material powder is preferably 1 or less.