Enhancing the durable performance of LiMn₂O₄ at high-rate and elevated temperature by nickel-magnesium dual doping

Various nickel and magnesium dual-doped LiNi_xMg_0.08Mn_1.92-xO₄ (x ≤ 0.15) were synthesized via a modified solid-state combustion method. All as-prepared samples show typical spinel phase with a well-defined polyhedron morphology. The Ni-Mg dual-doping obviously decreases the lattice parameter that gives rise to the lattice contraction. Owing to the synergistic merits of metal ions co-doping, the optimized LiNi_0.03Mg_0.08Mn_1.89O₄ delivers high initial capacity of 115.9 and 92.9 mAh·g^-1, whilst retains 77.1 and 69.7 mAh·g^-1 after 1000 cycles at 1 C and high current rate of 20 C, respectively. Even at 10 C and 55 °C, the LiNi_0.03Mg_0.08Mn_1.89O₄ also has a discharge capacity of 92.2 mAh·g^-1 and endures 500 cycles long-term life. Such excellent results are contributed to the fast Li⁺ diffusion and robust structure stability. The anatomical analysis of the 1000 long-cycled LiNi_0.03Mg_0.08Mn_1.89O₄ electrode further demonstrates the stable spinel structure via the mitigation of Jahn-Teller effect. Hence, the Ni-Mg co-doping can be a potential strategy to improve the high-rate capability and long cycle properties of cathode materials.