Heteroepitaxial oxygen-buffering interface enables a highly stable cobalt-free Li-rich layered oxide cathode

The oxygen redox process plays an essential role for the high charge-discharge capacity in Li-rich layered oxide (LLO) cathodes. The irreversible release of lattice oxygen may lead to surface reconstruction and cathode-electrolyte interfacial reactions, transition metal (TM) dissolution, as well as microcrack evolution, etc. during cycling that limit the commercial application of LLO cathodes. Herein, we propose the design of a heteroepitaxial Fluorite(CeO2)@Rocksalt@Layered interface with oxygen buffering effects in Cobalt-free Li1.2Mn0.53Ni0.27O2 through the incorporation of ceria. Experimental characterization and theoretical calculations reveal that the fluorite CeO2 nanolayer with oxygen vacancies suppresses the irreversible lattice oxygen loss and cathodeelectrolyte interfacial reactions in LLOs. Moreover, the synergy involving the formed rocksalt interphase and Ce3+ doping in the bulk not only stabilizes the structural integrity, resulting in substantial enhancement of capacity/voltage retention, but also accelerates the electrochemical kinetics upon cycling. This finding may pave the path for utilizing the reversible oxygen redox process and designing new high capacity TM-oxide cathode materials.