NOVELTY - The battery i.e. lithium ion secondary battery (10), has a battery case (20) for housing a wound electrode assembly (40). Nonaqueous electrolyte solution is housed in the battery case, where the nonaqueous electrolyte solution includes internal electrolyte solution and external electrolyte solution (80a). The internal electrolyte solution is contained in the wound electrode assembly. The external electrolyte solution is collected at a bottom part of the battery case, where viscosity of the internal electrolyte solution is greater than viscosity of the external electrolyte solution.    USE - Non-aqueous electrolyte secondary battery such as lithium ion secondary battery and vehicle drive battery, for a vehicle such as plug-in hybrid vehicle i.e. hybrid automobile, and electric motor-equipped automobile i.e. electric automobile. Can also be used for sodium ion secondary batteries and polymer lithium ion secondary batteries.    ADVANTAGE - The electrolyte required for charge/discharge lithium ion in a lithium ion secondary battery, can be maintained in interior of the wound electrode assembly, so that deterioration in battery characteristics, e.g. increase in resistance of lithium ion secondary battery and decline of input/output characteristics, can be prevented.    DETAILED DESCRIPTION - The internal electrolyte solution contains dimethyl carbonate as composition of solvent of the internal electrolyte solution. The external electrolyte solution contains dimethyl carbonate as composition of solvent of the external electrolyte solution. The solvent in the internal electrolyte solution and the solvent in the external electrolyte solution are a mixture of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate. An INDEPENDENT CLAIM is also included for a method for producing a non-aqueous electrolyte secondary battery.    DESCRIPTION OF DRAWING(S) - The drawing shows a partial cross-sectional view of a lithium ion secondary battery.    Lithium ion secondary battery (10)    Battery case (20)    Sealing plate (22)    Wound electrode assembly (40)    External electrolyte solution (80a)