To ensure safety of a battery by surely cutting off charging current even if battery temperature is sharply increased by reaching an overcharging state.

A positive electrode 10 has two layer structure of a first layer of a conductive layer 12 formed on a positive current collector 11 and a second layer of an active material layer 13 formed on the first layer. The conductive layer 12 of the first layer has at least a conductive filler, a binder, and a material decomposing at high potential (for example, 4.5-5.5 V) in an overcharging state, and the active material layer 13 of the second layer has at least a positive active material, a conductive agent, and a binder.