A battery pack includes a plurality of electrically connected battery modules. The battery module includes a plurality of type-A battery cells and a plurality of type-B battery cells. The type-A battery cells and the type-B battery cells are arranged in alternate manner. Both of the type-A and the type-B battery cells have a positive tab and a negative tab. The positive tabs and negative tabs of all type-A battery cells are electrically connected with a type-A first and a type-A second connecting pieces respectively. The positive tabs and negative tabs of all type-B battery cells are electrically connected with a type-B first and a type-B second connecting pieces respectively. When the battery pack burns, the type-A battery cells have an isolation effect on stopping the diffusion of combustion so as to improve the safety, and also improve the rapid charging and discharging ability and energy density of the battery pack.