GEL ELECTROLYTE FOR LITHIUM ION SECONDARY BATTERY AND LITHIUM ION SECONDARY BATTERY COMPRISING SAME

There is provided a lithium ion secondary battery which has high safety and good life characteristics. There is also provided a gel electrolyte for a lithium ion secondary battery, which contains a lithium salt, a copolymer of specific monomers, a compound having a specific phosphazene structure, and at least one compound selected from a specific cyclic disulfonate ester, a specific chain disulfonate ester and a specific sultone compound.