Si doping to passivate high-voltage medium-nickel low-cobalt layered oxide cathode reactivity enabling longer life lithium-ion battery

High-voltage medium-nickel low-cobalt lithium layered oxide cathodes show significant promise for lithium-ion batteries owing to their high capacity and cost-effectiveness. Nevertheless, the degradation of the bulk layered structure poses a serious threat to the cycle life for battery as charging voltage increases. Here, we employ a lattice doping strategy to enhance battery performance by introducing 1 mol% Si into the LiNi0.6Co0.05Mn0.35O2 (NCM) cathode material. X-ray diffraction (XRD) refinement results indicate that Si doping reduces the degree of Li+/Ni2+ mixing. Battery in-situ XRD analysis reveals that Si doping makes the H1/H2 phase transition from a two-phase reaction into a single-phase reaction. Variable-temperature in-situ XRD experiments demonstrate a improved phase transition trigger temperature. These improvements are attributed to Si doping passivates the layered oxide cathode reactivity due to no unpaired electrons and strong Si-O bond in Si4+. Consequently, Sidoped NCM (NCM-Si) exhibits an impressive 89.8 % capacity retention rate after 300 extended cycles, while the unmodified NCM only achieves 67.0 %. NCM-Si also demonstrates superior rate performance compared to NCM, with output capacities of 90 mAh g- 1 and 68 mAh g-1 at a high rate of 5C, respectively. This research offers valuable guidance strategies for the practical implementation of high-voltage medium-nickel low-cobalt cathodes.