磷酸铁锂锂离子电池电极过充衰减特性OA

Overcharging accelerates the degradation of lithium iron phosphate(LiFePO4)Li-ion battery and increases the risk of thermal runaway.Based on the three-electrode system,the single electrode of LiFePO4 Li-ion battery under overcharge condition is monitored in situ,the electrode decay behavior is identified from voltage and impedance.Firstly,qualitative and quantitative analysis of lithium deposition/stripping process is performed based on full battery voltage and differential voltage curve.Secondly,the electrode impedance is analyzed by electrochemical impedance spectroscopy(EIS)and Pearson correlation coefficient,the characteristic frequencies reflecting the electrode impedance are screened.Finally,the aging electrode materials are analyzed by SEM and energy dispersive X-ray spectroscopy(EDS).Overcharge cycling accelerates battery degradation and promotes irreversible lithium deposition.As the impedance of the battery increases,the cathode charge transfer resistance dominates the impedance response in the low-frequency region,whereas the anode solid electrolyte interphase(SEI)film resistance governs the mid-frequency region.SEI film formation on the anode leads to active lithium loss,while particle cracking in cathode results in active material loss.