LITHIUM ION SECONDARY BATTERY

摘要

PROBLEM TO BE SOLVED: To minimize the entry of both of phosphoric ester and a lithium ion into graphite and to suppress the expansion and shrinkage of a Si material in a lithium ion battery having a phosphoric ester.SOLUTION: A lithium ion secondary battery comprises: a positive electrode; a negative electrode; and an electrolytic solution. The electrolytic solution has a compound expressed by the formula (1). The negative electrode has a graphite negative electrode active material and a Si composite material; in Si composite particles, no more than 50 nm of Si crystallites are dispersed in a matrix consisting of a Si oxide or Si alloy.SELECTED DRAWING: Figure 1