LITHIUM ION SECONDARY BATTERY

摘要

PROBLEM TO BE SOLVED: To provide a battery less in capacity lowering caused by high- temperature storage and superior in reliability by including tetraphenyl borate in organic electrolytic solution formed by dissolving electrolyte in organic solvent by a specific range wt.% relative to the whole electrolytic solution as solvent decomposition depressant. SOLUTION: A lithium ion secondary battery is formed by adding tetraphenyl borate to organic electrolytic solution. The content of the tetraphenyl borate is from 0.001 wt.% to 1.0 wt.%. It is used at the relatively low concentration and the purpose of the addition is to provide an effect of suppressing the decomposition of solvent. The tetraphenyl borate having such molecule structure as physically impossible to be incorporated in positive/negative electrode active materials is added thereto so that the state of solvation of the electrolyte is changed relative to the lithium ions on the electrode interface so that the decomposition of the electrolyte on the electrode interface is suppressed. The suppression of the decomposition of the electrolyte on the electrode interface can suppress the lowering of the capacity of the secondary battery in stored at high temperature.