To provide an electrolyte and a battery capable of improving cycle characteristics after preservation at high temperature.

A cathode 21, an anode 22 and an electrolyte 24 are housed in a film-shaped sheathing member 30. The electrolyte 24 contains polymeric compound and electrolyte liquid in which the polymeric compound is retained, and gelatinized. The electrolyte liquid contains a solvent containing γ-valerolactone to within a range of not lower than 0.5 wt% and not higher than 10 wt%, and vinyl ethylenecarbonate to within a range of not lower than 0.5 wt% and not higher than 5 wt%. By this, the cycle characteristics, after preservation at a high temperature is improved, without lowering the initial characteristics.