Investigation of self-discharge properties and a new concept of open-circuit voltage drop rate in lithium-ion batteries

In this work the self-discharge characteristics are evaluated through resting OCV (open-circuit voltage)-SOC (state-of-charge) hysteresis and storage aging behavior for pouch NCM|graphite lithium-ion battery. A weak peak is found on the OCV-SOC curve of incremental capacity and differential voltage analysis. A low free-energy complex model involving the formation of an absorbed electron-lithium-ion solvation sheath on the graphite surface is proposal for this weak reaction. The electrons are shared between the graphite and electrolyte via lithium-ion. Results of batteries aging tests reveal a strong linear relation of OCV vs. square-root of time, where the dissociation of complex is considered as the mechanism. The dependency of the square-root of time demonstrates that a new concept of voltage drop rate (mV h−1/2) is more feasible by reducing the influence of OCV checking time from 120% to 26%.