Confining oxygen anion to stabilize layered oxide Li1.2Ni0.2Mn0.6O2 via Zr-Al dual doping

Abstract

Lithium-rich manganese-based transition metal oxide Li_1.2Ni_0.2Mn_0.6O₂ (LNMO) can achieve high energy density due to the interaction of anionic redox kinetics in Li₂MnO₃. However, the irreversible release of oxygen and migration of Mn ions during deep de-lithiation disrupts the layer structure of LNMO, leading to a decrease in voltage and capacity. Herein, we confine oxygen anion through Zr and Al co-doping. Combined analysis of structure refinement, XPS and XAS, the co-doped strategy effectively prohibits cation disordering of Li/Ni, inhibits the Jahn-Teller effect and reduces the transition metal (TM) and oxygen hybridization. As a result, the Zr and Al co-doping LNMO sample (ZA-LNMO) possesses a capacity retention of 92% after 100 cycles and 86% after 200 long-term cycles, much higher than the value of the undoped sample (79% for 100 cycles and 58% for 200 cycles). Even at the harsh conditions such as ultra-high current rate (10 C) or high temperature (60 °C), ZA-LNMO also maintains 70% retention after 200 cycles. Our findings provide an insight into the synergistic effect of cation co-doping and help to design layered oxides for future applications.