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1. (WO2013157620) NEGATIVE ELECTRODE ACTIVE MATERIAL FOR LITHIUM ION SECONDARY BATTERY AND LITHIUM ION SECONDARY BATTERY

Pub. No.:    WO/2013/157620    International Application No.:    PCT/JP2013/061561
Publication Date: Fri Oct 25 01:59:59 CEST 2013 International Filing Date: Sat Apr 20 01:59:59 CEST 2013
IPC: H01M 4/587
H01M 4/36
Applicants: HITACHI, LTD.
株式会社 日立製作所
Inventors: NISHIMURA Etsuko
西村 悦子
TANAKA Akihide
田中 明秀
TAKAMATSU Daiko
高松 大郊
HIRANO Tatsumi
平野 辰己
OKABE Keiji
岡部 圭児
Title: NEGATIVE ELECTRODE ACTIVE MATERIAL FOR LITHIUM ION SECONDARY BATTERY AND LITHIUM ION SECONDARY BATTERY
Abstract:
Conventionally, the volume of a negative electrode active material changes during a charge-discharge cycle and the conductive network inside the negative electrode gradually degrades. As a result, there is a problem that the capacity of the negative electrode decreases. To address the problem, the purpose of the present invention is to minimize the decrease in the capacity of a negative electrode and to extend the life of a lithium ion secondary battery. A negative electrode active material for lithium ion secondary battery is characterized by including a graphite nuclear material and a covering layer for covering the surface of the nuclear material wherein the thickness of said covering layer is 1 to 200 nm and the bulk modulus of said covering layer is smaller than the bulk modulus of said nuclear material.