100 Wh large size Li-ion battery with safety structures were developed. Specific energy and energy density of the battery were 110 Wh/kg and 200 Wh/1, respectively. Safety tests: nail penetration test, external short circuit test, overcharge test and externally heating test were carried out to determine the fundamental safety level of the battery. Behavior such as ignition and explosion of the battery were not observed during the safety tests. The battery is considered to be applicable to electric vehicles and hybrid electric vehicles.