Patent ID: 8137846

Claim:
A nonaqueous-electrolyte secondary battery comprising a negative electrode and a positive electrode each capable of occluding/releasing lithium, a separator, and a nonaqueous electrolyte solution comprising a nonaqueous solvent and a lithium salt, wherein the separator comprises a porous film made of a thermoplastic resin containing an inorganic filler, and at least either of the following is satisfied: the active material contained in the negative electrode is a particulate active material having an aspect ratio of from 1.02 to 3; or the active material contained in the positive electrode is a particulate active material having an aspect ratio of from 1.02 to 1.5, and wherein the porous film of the separator is obtained by a process comprising: at least one of mixing, melting and kneading a resin mixture comprising the inorganic filler, the thermoplastic resin and an antioxidant, to form a resin composition; forming a resin sheet from the resin composition; and stretching the resin sheet to form the porous film, and wherein the inorganic filler is at least one of barium sulfate and alumina and is present in the porous film in an amount of 100 parts by weight or more per 100 parts by weight of the thermoplastic resin, wherein when the electrolyte solution comprises a mixed nonaqueous solvent solution obtained by dissolving LiPF 6 into a mixed nonaqueous solution comprising ethylene carbonate and ethyl methyl carbonate in a volumetric ratio of 3:7 and contains LiPF 6 at a concentration of 1 M, the filler achieves a lithium ion concentration of more than 0.75 mmol/g in the electrolyte solution after adding the filler thereto at a ratio of 0.5 g to 1 ml of the electrolyte solution, and then retaining the electrolyte solution at 85° C. for 72 hours.