Patent ID: 8067120

Claim:
A non-aqueous electrolyte secondary battery comprising: a positive electrode comprising a lithium-containing transition metal oxide as a positive electrode active material; a negative electrode; a separator and a reduction-resistant film interposed between said positive electrode and said negative electrode; and a non-aqueous electrolyte, wherein: said non-aqueous electrolyte comprises a non-aqueous solvent and a solute dissolved in said non-aqueous solvent, said non-aqueous solvent consisting essentially of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether and sulfolane, said separator has a thickness of 54 to 300 μm and is in contact with said positive electrode, said reduction-resistant film is in contact with said negative electrode, said separator comprises polytetrafluoroethylene, and said reduction-resistant film comprises at least one of polyethylene film and polypropylene film.