Effect of overcharge on entropy and enthalpy of lithium-ion batteries

We have investigated the evolution of the thermodynamics behaviour and of the crystal structure of electrodes materials of lithium-ion batteries based on graphite anode and lithium cobalt oxide (LCO) cathode after applying high voltage charging between 4.2 V and 4.9 V cut-off voltages (COV). We found the entropy and enthalpy profiles vary dramatically with the applied COV. These changes correlate well with the anode and the cathode crystal structure degradation as evidenced by post-mortem X-ray diffractometry and Raman scattering spectrometry. Our finding is thermodynamics measurements can be used as a new and non-destructive investigation tool to characterize the degradation level of electrode materials and consequently assess the cell's state of health (SOH).