Analysis of degradation of electrolytic Fe, Co, Ni sulfides and their graphitized analogs in lithium battery using impedance spectroscopy

Changes in parameters of complex-plane plots are analyzed for electrolytic Me _x S _y electrodes (Me = Fe, Co, Ni) and their graphitized analogs contacting electrolyte (ethylene carbonate, dimethyl carbonate, 1 M LiClO₄) in the case of degradation in a layout lithium battery at cycle 15. Impedance measurements in the high- and medium-frequency region of complex-plane plots revealed the key role of the surface solid-phase film and also of resistance of charge transfer through the sulfide material/electrolyte interface in degradation of Me _x S _y electrodes under cycling in the potential range of 2.80?0.02 V vs. Li/Li⁺. The activation energy is determined for processes of charge transfer through the electrode/electrolyte interface.