Patent ID: 7727676

Claim:
A nonaqueous electrolyte secondary battery, comprising: an electrode group including a positive electrode, a negative electrode and a separator arranged between the positive electrode and the negative electrode, the positive electrode including a collector and a positive electrode layer that is formed on one or both surfaces of the collector and contains an active material, and the negative electrode including a collector and a negative electrode layer that is formed on one or both surfaces of the collector and contains a material for absorbing-desorbing lithium ions; a nonaqueous electrolyte impregnated in the electrode group and including a nonaqueous solvent and a lithium salt dissolved in the nonaqueous solvent, the nonaqueous solvent containing 40 to 95% by volume of γ-butyrolactone based on the total amount of the nonaqueous solvent; and a jacket for housing the electrode group, the jacket being made of a sheet which has a thickness of 0.05 mm to 0.35 mm and includes a resin layer, wherein the positive electrode layer has a porosity lower than that of the negative electrode layer, the positive electrode layer has a thickness of 10 to 60 μm, and the negative electrode layer has a thickness of 10 to 65 μm.