Quantitative analysis of side-reaction rates and capacity fading mechanisms in all-solid-state Li-ion batteries

The all-solid-state Li-ion batteries (LIBs) exhibit far superior lifetime performances than the liquid-based LIBs, rendering them suitable for ultra-long-term applications, particularly at high temperatures. To predict the lifetimes of the all-solid-state LIBs, which are critical for long-term applications, elucidating the capacity fading mechanism is essential. In this study, we quantitatively evaluated the side-reaction rates of lithium titanium oxide (Li[Li 1/3 Ti 5/3 ]O 4 ; LTO) and lithium cobalt oxide (LiCoO 2 ; LCO) in all-solid-state symmetric cells and compared the results with those of the all-solid-state LTO/LCO batteries to investigate the capacity fading mechanism. The side-reaction rates of LTO and LCO electrodes calculated by the all-solid-state symmetric cells were extremely low, indicating that the electrochemical stability of the interface between the solid electrolyte and oxide active material was substantially higher than that of the organic electrolyte. This enhanced interface stability is a key factor contributing to the excellent long-term performance of the all-solid-state LIBs. Moreover, the capacity fading rate of the all-solid-state LTO/LCO batteries measured in the long-term cycling tests was successfully predicted based on the side-reaction rates determined by the symmetric cells. This quantitative lifetime prediction approach enables the design of all-solid-state LIBs with superior safety and reliability. • Kinetic analysis reveals capacity fading mechanisms in the solid-state batteries. • The quantitative evaluation of the side reaction currents of electrodes. • Symmetric cells confirm low side reaction rates at 105 °C. • Solid-state batteries show significantly slower side reactions than liquid systems.