Self-discharge of secondary lithium-ion graphite anodes

A new method for measuring self-discharge of lithium-ion graphite anodes is reported. First, the anode lithium content is calculated from the open-circuit potential as a function of open-circuit time (OCP versus OCT) using equilibrium potential–composition isotherms. Then, the self-discharge rate is obtained from the differential of lithium content with respect to time on open circuit. The self-discharge rate measured by this means after the first charge–discharge cycle to 0.0 V versus Li/Li+ is largely controlled by the growth of the solid electrolyte interphase (SEI) film, with some influence from stage transformation.