NOVELTY - A non-aqueous electrolyte secondary battery comprises flat electrode assembly having positive electrode (18) and negative electrode, bottomed prismatic hollow outer can storing flat electrode assembly and non-aqueous electrolyte and having opening portion; and sealing plate (23) sealing opening portion of hollow outer can (25), where non-aqueous electrolyte containing at least one of lithium salt having oxalate complex as anion and lithium difluorophosphate at time of making non-aqueous electrolyte secondary battery, and outer surface area of battery outer body including hollow outer can.    USE - As non-aqueous electrolyte secondary battery (claimed), used as a power supply for driving portable electronic equipment, such as cell phones including smartphones, portable personal computers, PDAs, and portable music players.    ADVANTAGE - The non-aqueous electrolyte secondary battery solves the problems regarding heat generation of a battery and regarding a lowering of output characteristics in a low temperature environment.    DETAILED DESCRIPTION - A non-aqueous electrolyte secondary battery comprises flat electrode assembly including positive electrode (18) and negative electrode, bottomed prismatic hollow outer can storing the flat electrode assembly and non-aqueous electrolyte and having an opening portion; and a sealing plate (23) sealing the opening portion of the hollow outer can (25), where the non-aqueous electrolyte containing at least one of a lithium salt having an oxalate complex as an anion and lithium difluorophosphate at the time of making the non-aqueous electrolyte secondary battery, and the outer surface area of a battery outer body including the hollow outer can and the sealing plate being greater than or equal to 350 cm2.    DESCRIPTION OF DRAWING(S) - The figure shows cross-sectional view of non-aqueous electrolyte secondary battery.    Winding electrode assembly (14)    Positive electrode substrate exposed portion (15)    Positive electrode collector (17)    Positive electrode (18)    Insulating members (21, 22)    Sealing plate (23)    Insulating sheet (24)    Hollow outer can (25)    Current interruption mechanism (27)    Positive electrode conductive members (29)    Positive electrode intermediate member (30)