Lithium Ion Secondary Battery And Electrolyte Additive For The Same

Provided is an electrolyte additive for a lithium ion secondary battery including an organic lithium compound and a hyper-branched structure material. The electrolyte additive enhances the decomposition voltage of the electrolyte up to 5.5 V, and increases the heat endurable temperature by 10 DEG C. or more. The safety of the battery is thus improved.