Disclosed herein is a battery cell including an electrode assembly of a cathode/separator/anode structure, the electrode assembly being impregnated with electrolyte, the electrode assembly being chargeable and dischargeable, a battery case in which the electrode assembly is mounted, the battery case being made of aluminum or an aluminum alloy, and a protective coating layer applied to at least a portion of an outer surface of the battery case, the protective coating layer containing an electrically insulative polymer material.