Electrolyte additive for secondary battery, preparation method therefor, and electrolyte composition and secondary battery, which comprise additive

A method of manufacturing an electrolyte additive comprising:

• a step of reacting hexafluorophosphate and 2-monofluoromalonic acid;
• a step of adding a HF scavenger to a mixed solution produced by the reaction;
• and
• a step of concentrating and drying the solution obtained from the above to prepare a compound represented by Chemical Formula 1 or Chemical Formula 2 below:
• wherein M is alkali metal, and
• R is hydrogen, a substituted or unsubstituted C1 to C5 alkyl group, a substituted or unsubstituted C1 to C5 perfluoroalkyl group, a substituted or unsubstituted C6 to C30 aryl group, a substituted or unsubstituted C6 to C30 perfluoroaryl group, or CF3.

An electrolyte composition comprising:

• an electrolyte additive;
• a non-aqueous organic solvent;
• and
• an alkali salt,
• wherein the electrolyte additive includes a compound represented by Chemical Formula 2 below:
• wherein M is alkali metal, and
• R is hydrogen, a substituted or unsubstituted C1 to C5 alkyl group, a substituted or unsubstituted C1 to C5 perfluoroalkyl group, a substituted or unsubstituted C6 to C30 aryl group, a substituted or unsubstituted C6 to C30 perfluoroaryl group, or CF3.

A secondary battery comprising:

• a cathode containing a cathode active material;
• an anode containing an anode active material;
• and
• an electrolyte containing an electrolyte additive represented by Chemical Formula 2 below:
• wherein M is alkali metal, and
• R is hydrogen, a substituted or unsubstituted C1 to C5 alkyl group, a substituted or unsubstituted C1 to C5 perfluoroalkyl group, a substituted or unsubstituted C6 to C30 aryl group, a substituted or unsubstituted C6 to C30 perfluoroaryl group, or CF3.