A Mg-Doped High-Nickel Layered Oxide Cathode Enabling Safer, High-Energy-Density Li-Ion Batteries
High-nickel layered oxide cathodes with a Ni content of > 90% show substantial potential for next-generation lithium-ion batteries (LIBs) due to their high capacity and lower cost. However, they are plagued by rapid capacity decay and poor thermal stability, which hamper their practical viability. Here we present Li 0.98 Mg 0.02 Ni 0.94 Co 0.06 O 2 (NC-Mg) with 2% Mg doping, aiming to provide a strategic guideline for solving the issues. The Mg 2+ ions occupy the lithium layer and are pro-posed to act as pillar ions, which substantially enhances the structural reversibility and reduces the anisotropic lattice distortion upon cycling, thereby greatly improving the electrochemical and thermal stability of NC-Mg compared to the undoped LiNi 0.94 Co 0.06 O 2 (NC). Specifically, NC-Mg delivers 214 mA h g -1 with a capacity retention of 80.1% after 500 cycles in pouch-type full cells, much higher than the retention of NC (56.3%). A discharge capacity of 158 mA h g -1 at 10C rate demonstrates its remarkable rate capability. Additionally, the Mg doping significantly elevates the exothermic peak tem-perature of NC-Mg to 211 °C, in sharp contrast to 177 °C for NC, highlighting the improved thermal stability of NC-Mg. Collectively, the superior performance of NC-Mg demonstrates a feasible alternative strategy for developing safer, high-energy-density LIBs.