Patent ID: 7220518

Claim:
A secondary battery comprising a positive electrode, a negative electrode and an electrolyte, wherein the electrolyte comprises a first anion expressed by Chemical formula 5 and a second anion expressed by Chemical formula 6, wherein Chemical formula 5 is PF a Q b R c − and Q expresses at least one compound selected from the group consisting of CF 3 , C 2 F 5 , and C 3 F 7 , R expresses SO 2 CF 3 or SO 2 C 2 F 5 , and a, b and c satisfy 1≦a≦5, 0≦b≦5 and 0≦c≦5, and a+b+c=6; and a, b, c is an integer, wherein Chemical formula 6 is N(C n F 2n+1 So 2 ) 2 − and n satisfies 1≦n≦2.