Patent ID: 8455132

Claim:
A lithium ion secondary battery comprising: a positive electrode; a negative electrode; a non-aqueous electrolyte; and a separator interposed between said positive electrode and said negative electrode; wherein said separator comprises a polyolefin layer and an oxidation-resistant layer, said oxidation-resistant layer comprises an oxidation-resistant polymer and an inorganic filler, said oxidation-resistant polymer includes at least one selected from the group consisting of polyimide, aramid, and a polyamideimide, a main chain of said oxidation-resistant polymer includes neither a —CH 2 — group nor a —CH(CH 3 )— group, said oxidation-resistant layer faces said positive electrode, said polyolefin layer faces said negative electrode, the thickness of said oxidation-resistant layer is 2 to 10 μm, the total thickness of said oxidation-resistant layer and said polyolefin layer is 10 to 25 μm, a cut-off-voltage of charge is set to 4.4 V or more, the negative electrode includes a negative electrode active material, and the negative electrode active material is a material including Si.