Energy Density Theory of Lithium-Ion Capacitors

As a new generation of capacitors, lithium-ion capacitors (LICs) have the same power density and cycle life as traditional electric double-layer capacitors, and 2-5 times the energy density. For the first time, in this paper we derive the mathematical formulas for the energy density of LICs. These formulas describe the relationship between the energy density of LICs and all the critical parameters, including the specific capacities of anode (negative) and cathode (positive) electrodes, the capacity ratio of anode to cathode electrodes, the maximum and minimum voltages of the LICs, the specific capacity of pre-lithiation source and the degree of the pre-lithiation and so on. These formulas provide not only a clear direction for future research in materials and devices of LICs, but also a useful tool for LIC design.