Improving cycling performance of Li-rich layered cathode materials through combination of Al2O3-based surface modification and stepwise precycling

Abstract Controlling a cathode/electrolyte interface by modifying the surface of a cathode material with metal oxides or phosphates is a concept being explored as a possible strategy for improving the electrochemical performance of such materials. This study therefore looks at the crystal structure and chemical bonding state from bulk to surface of Al 2 O 3 -coated Li[Li 0.2 Ni 0.18 Co 0.03 Mn 0.58 ]O 2 and explores the influence that surface modification has on the electrochemical performance. Investigation by X-ray diffraction, hard X-ray photoelectron spectroscopy (HAXPES) and galvanostatic charge/discharge reaction reveals that the surface-modification layer is composed of Li–Al oxides and Al oxides, with a Li M 1− x Al x O 2 ( M  = transition metal) interlayer formed between the modification layer and Li[Li 0.2 Ni 0.18 Co 0.03 Mn 0.58 ]O 2 particles. The cycling performance of the Li-rich layered oxide is enhanced by its surface modification with Al 2 O 3 , achieving a discharge capacity of more than 310 mA h −1 and excellent cycling stability at 50 °C when combined with a more gradual Li-insertion/de-insertion process (i.e., stepwise precycling treatment).