Probing solid-state battery aging: evaluating calendar vs. cycle aging protocols via time-resolved electrochemical impedance spectroscopy†

Understanding battery aging mechanisms is critical towards identifying and improving upon performance bottlenecks. Aging protocols which can quickly identify and monitor degradation of cells can help expedite solid-state battery development by predicting the possible long-term aging trend of cells in a time efficient manner. In this work, the degradation behavior of In/InLi|Li₆PS₅Cl|NCM83:Li₆PS₅Cl cells was investigated using two different accelerated aging protocols: (1) calendar aging and (2) cycle aging. Cells with various cut-off potentials were investigated using the two aging protocols showing significantly greater performance deterioration under calendar aging relative to cycle aging. Applying distribution of relaxation times analyses obtained from impedance spectroscopy, the cathode–electrolyte interfacial resistance evolution is found to be the dominant degradation mechanism during calendar aging while changes at the anode–electrolyte interface are influential during cycle aging tests. The aging protocol and analyses applied in this work can potentially be further extended to other systems to help understand degradation processes and quickly screen cells for optimization.