Mitigation of Oxygen Evolution and Phase Transition of Li-Rich Mn-Based Layered Oxide Cathodes by Coating with Oxygen-Deficient Perovskite Compounds.

Li-rich Mn-based layered oxide cathodes with a high discharge capacity hold great promise for high energy density lithium-ion batteries. However, application is hampered by voltage and capacity decay and gas evolution during cycling due to interfacial side reactions. Here, we report coating by oxygen-deficient perovskite LaSrCoO using the Pechini process. X-ray photoelectron spectroscopy and scanning transmission electron microscopy both exhibit a uniform coating layer with a high oxygen vacancy concentration. The coating effectively mitigates the first cycle irreversible capacity loss and voltage decay while increasing cyclability. Optimized coating improves capacity retention from 55.6% to 84.8% after 400 cycles at 2 C. differential electrochemical mass spectroscopy shows that such a coating can significantly mitigate the release of oxygen and carbon dioxide. Electrochemical impedance spectroscopy and post-mortem analysis indicate that the coating layer forms a stable interface and restricts structure evolution and cation mixing during cycling, conferring these cathode materials with better cycling and voltage stability. The perovskite can be applied to other cathodes with high voltage and capacity to suppress interfacial side reactions toward developing stable high energy density batteries.