Electrolyte for lithium ion secondary battery and lithium ion secondary battery comprising the same

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 R1 and R2 are respectively selected from the group consisting of hydrogen, a halogen group, a cyano group (CN), a nitro group (NO2), a vinyl group and a fluorinated alkyl group having 1 to 5 carbons, where R1 and R2 are not both hydrogen.