Patent ID: 8632916

Claim:
A lithium ion polymer battery comprising: a positive electrode plate formed with a positive electrode mixture layer having a lithium composite oxide as a positive electrode active material; a negative electrode plate; a separator; and a gel nonaqueous electrolyte, the positive electrode active material having an average particle diameter of 4.5 to 15.5 μm and a specific surface area of 0.13 to 0.80 m 2 /g, the positive electrode mixture layer containing at least one coupling agent represented by General Formula (I) at a content of 0.01% by mass or more and 5% by mass or less with respect to the mass of the positive electrode active material, and the gel nonaqueous electrolyte being formed from a nonaqueous electrolyte containing a monomer having a (meth)acrylic end group: (where M is one atom selected from Al, Ti, and Zr, each of R1 and R2 is an alkyl group or an alkoxy group having 1 to 18 carbon atoms, and n represents an integer of 1 to 4); wherein a part of the coupling agent is thermally decomposed by short circuit heat at the time of nail penetration to form an insulating layer between the polymer electrolyte and the positive electrode mixture.