Lithium ion secondary batteries gel electrolyte and a lithium ion secondary battery comprising the same

It has a high safety, and a lithium ion secondary battery having good life characteristics. A lithium salt, a copolymer of a specific monomer, a compound having a specific phosphazene structure, specific cyclic disulfonic acid ester, at least one or more selected from a particular chain disulfonic acid esters and certain sultones compound lithium ion secondary batteries gel electrolyte containing the compound.