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 cathode-electrolyte 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.