A battery capable of obtaining the superior battery performance is provided. An electrolyte is a gel electrolyte containing an electrolytic solution and a polymer compound. The polymer compound contains a ternary system copolymer containing vinylidene fluoride, hexafluoropropylene, and monomethylmaleic acid ester as a component. The copolymerization amounts of hexafluoropropylene and monomethylmaleic acid ester in the ternary system copolymer are respectively in the range from 4 wt % to 7.5 wt %, and in the range from 0.3 wt % to 2 wt %. Further, the weight average molecular weight of the ternary system copolymer is in the range from 0.6 million to 1.5 million. The liquid retaining characteristics of the electrolyte are improved. Therefore, the contact characteristics of the electrolyte to a cathode, an anode, and a separator are improved.