Construction of a hetero-epitaxial nanostructure at the interface of Li-rich cathode materials to boost their rate capability and cycling performances

Lithium-rich cathode materials are considered to be promising candidate cathode materials for next-generation Li-ion batteries owing to their high specific capacities and low cost. Nevertheless, they still suffer from undesirable capacity loss and voltage decay during cycling. In this work, we propose a facile strategy to coat lithiated transition metal phosphates on the surface of Li-rich cathode materials. Strikingly, the coated material shows a hetero-epitaxial nanostructure at the interface between the coating layer and the cathode material. Such a coating layer with a unique interfacial structure could effectively boost the Li⁺ solid-state diffusion kinetics, protect the cathode material from the corrosion of the electrolyte, and suppress the oxygen loss during the charge-discharge processes. Moreover, the lithiated phosphate coating layer can inhibit the formation of residual Li compounds upon long-term storage under an ambient atmosphere. Based on the above favorable properties, the lithiated phosphate coated Li-rich cathode material shows a high rate capability with a discharge capacity of 156 mA h g^-1 obtained at 5 C and decent cyclic stability with a capacity retention of 93.4% achieved at 0.5 C after 140 cycles. This study investigates the interfacial engineering of Li-rich cathode materials via the construction of a Li⁺-conductive lithiated phosphate coating layer with a hetero-epitaxial interfacial nanostructure, which may offer an effective way to further improve the electrochemical performances of Li-rich cathode materials.