Structural Degradation of High Voltage NMC Cathodes in Solid-State Batteries and Implications for Next Generation Energy Storage

In this study we report the stability of the layered high voltage cathode NMC622 with respect to a standard liquid electrolyte and in an all solid-state configuration. NMC622 cathodes with a (104) orientation were found to suffer from degradation at high voltage (4.5V vs. Li/Li+) due to electrolyte promoted degradation of the layered structure; the Lipon layer was able to suppress the extent of this decomposition but not totally prevent it from occurring. In the solid-state cells the capacity decreased from 203 mAh/g to 93 mAh/g in the first cycle and from 93 mAh/g to 79 mAh/g over the subsequent 99 cycles whereas after twenty cycles the liquid cell charge capacity was dominated by the irreversible electrolyte degradation. The interfacial resistance of the solid-state cells was stable with cycling, suggesting minimal degradation of the NMC622/Lipon interface and incumbent losses due to structural evolution associated with cathode orientation. This data indicates that accessing stable high voltage capacity...