To improve battery characteristics such as storing property and charge/discharge cycle characteristics, in a non-aqueous electrolyte secondary battery having a polymer electrolyte obtained by heating a non-aqueous electrolyte containing a radical polymeric monomer and polymerizing the monomer.

A vinyl ethylene carbonate is contained in the non-aqueous electrolyte to perform polymerization of the radical polymeric monomer at a temperature at which 70% or more of the volume of the vinyl ethylene carbonate remains unpolymerized, for example, at 50°C or lower.

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