Study on aging characteristics and failure mechanism of lithium-ion battery under slight-overcharge cycling
In real-world applications,lithium-ion batteries can occasionally undergo slight overcharging due to inconsistency within the battery pack or malfunctions in the charging system.Prolonged exposure to such overcharge conditions can pose significant safety hazards.To investigate the effects of slight-overcharge cycling on the aging characteristics and failure mechanisms of lithium-ion batteries,experiments were conducted with batteries subjected to different cut-off voltages during overcharging.The aging analysis was analyzed using electrochemical impedance spectroscopy(EIS),distribution of relaxation time(DRT),and incremental capacity analysis(ICA).These techniques were further corroborated by scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDS)and X-ray photoelectron spectroscopy(XPS)on disassembled electrodes.The experimental results show that slight-overcharge cycling significantly accelerates battery aging compared to normal cycling,leading to a more rapid decline in specific capacity.Additionally,as the number of cycles increases,the depletion of lithium ions and active materials within the battery is expedited,leading to a noticeable increase in various types of battery impedance.Notably,the charge transfer resistance of batteries cycled at 4.5 V slight-overcharge increased by 196.15% from their initial state.This overcharging condition also exacerbates battery polarization and deteriorates the cycling stability of the materials.Post-cycling analysis revealed that slight-overcharge cycling causes active materials to detach from the current collectors,with significant fracturing observed in in the cathode's active particles and thickening of the solid electrolyte interface(SEI)film on the anode.Additionally,there was a notable increase in the contents of F and P elements.
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