Battery pack and electric vehicle

摘要

A battery pack which is constituted by a plurality of lithium secondary batteries and which can prevent performance deterioration and has a long life is provided. The battery pack is manufactured by connecting in series four lithium ion batteries in which a lithium cobaltate is used for a positive active material and an amorphous carbon is used for a negative active material. In the battery, a percentage of the difference between positive electrode charging capacity and negative electrode charging capacity to capacity of the lithium secondary battery was set to 6%. The SOC difference among the four batteries was adjusted to 6 points or less. Even a battery having a low SOC is full charged, lithium oversupplied does not exceed a lithium amount capable of being occluded by a negative electrode at a battery having a high SOC, and thereby the active material does not deteriorate.