Nb-doping strategy to enable superior cyclability for high-nickel Li-rich oxide cathodes

Li-rich layered oxides (LLOs) offer a high reversible capacity, however, their commercial application is seriously impeded by rapid voltage decay and capacity degradation. Increasing Ni content in LLOs materials is regarded as a viable strategy to address this issue and has attracted current research interests but is normally accompanied by inferior cycling stability and reduced capacity. Herein, an effective strategy is proposed to enhance the performance of high‑nickel lithium-rich Mn-based oxides Li_1.13Mn_0.48Ni_0.33Co_0.06O₂ (LLMO) through Nb doping. Specifically, the optimized Ni excess cathode LLMO-Nb3 furnishes discharge capacities and energy densities of 199 mAh g^-1 and 222 Wh kg^-1 compared to 125 mAh g^-1 and 136 Wh kg^-1 of pristine LLMO after 200 cycles at 1.0C. The robust NbO bonds and the pillaring effect of inactive Nb are capable of effectively stabilizing the oxygen lattice framework as well as suppressing the capacity and voltage fading upon cycling; the LLMO-Nb3 material achieves an impressive capacity retention of 91.46% after 300 cycles at 0.5C and 94.86% after 200 cycles at 1.0C as well as exhibits a superior midpoint voltage attenuation of 0.8 mV per cycle over 200 cycles at 1.0C. Concurrently, the cathode electrolyte interfacial (CEI) stability is improved by this synergistic regulation strategy combining increased Ni content with Nb doping, thus preventing the rapid performance decay of LLMO. This study proposes a novel strategy for fabricating high-performance high‑nickel Li-rich cathodes by doping proper alien elements, providing valuable guidance for the design of advanced cathode materials targeting high energy density lithium-ions batteries.