Patent ID: 8771881

Claim:
An electrolyte for a lithium ion secondary battery comprising: a non-aqueous organic solvent; lithium salt; and a phosphonitrile fluoride trimer represented by a chemical formula 1 below as an additive: wherein the amount of the phosphonitrile fluoride trimer of the chemical formula 1 is 0.1 to 1 parts by weight based on 100 parts by weight of the total electrolyte, wherein the non-aqueous organic solvent comprises at least one selected from the group consisting of a carbonate, an ester, an ether and a ketone, wherein the non-aqueous organic solvent further comprises at least one of benzene, fluorobenzene, bromobenzene, chlorobenzene, toluene, xylene, mesitylene or a mixture thereof, and wherein the electrolyte further comprises at least one selected from the group consisting of vinylene carbonate, propene sultone and an ethylene carbonate group compound represented by a chemical formula 2: where R 1 and R 2 are respectively selected from the group consisting of hydrogen, a halogen group, a cyano group (CN), a nitro group (NO 2 ), a vinyl group and a fluorinated alkyl group having 1 to 5 carbons, where R 1 and R 2 are not both hydrogen.