Battery energy density refers to the electrical energy released by a unit mass or volume of the battery. The higher the battery's energy density, the more electrical energy is stored per unit mass or volume. The basic unit is Wh/kg (watt-hours per kilogram).
Battery energy density consists of two concepts: single cell energy density and battery system energy density. Since the battery system includes not only the cells but also other components such as circuit systems and thermal management systems, generally speaking, the energy density of a single cell is greater than that of the battery system. Currently, the energy density of mainstream pure electric vehicle battery systems is between 140 and 180 Wh/kg.