A lithium ion secondary battery including: an electrode group including a
belt-like positive electrode and a belt-like negative electrode that are
wound with a separator interposed therebetween; and a can with a bottom
for accommodating the electrode group, wherein the positive electrode has
a positive electrode current collector and a positive electrode mixture
layer carried on the positive electrode current collector, the negative
electrode has a negative electrode current collector and a negative
electrode mixture layer carried on the negative electrode current
collector, and a porous heat-resistant layer is partially provided
between the separator and at least one of the positive electrode mixture
layer and the negative electrode mixture layer. Since a porous
heat-resistant layer is thus placed, a high performance lithium ion
secondary battery capable of efficiently preventing internal short
circuit due to overheating while preventing decrease in battery
characteristics can be provided.