High rate capability performance of cobalt-free lithium-rich Li_1.2Ni_0.18Mn_0.57Al_0.05O₂ cathode material synthesized via co-precipitation method

Lithium-rich nickel manganese cobalt oxide (LR-NMC) cathode materials have been considered in next-generation Li-ion batteries for electric vehicles due to their high energy density and cost-effectiveness. However, LR-NMC cathode materials suffer from poor rate capability and cyclic stability. In addition, the reliance on environmentally harmful and expensive cobalt resources presents an additional challenge for cobalt-containing cathode materials. To overcome these challenges, two cobalt-free lithium-rich cathode material compositions, Li_1.2Ni_0.2Mn_0.56Al_0.04O₂ (LR-NMA-1) and Li_1.2Ni_0.18Mn_0.57Al_0.05O₂ (LR-NMA-2), are designed and synthesized via co-precipitation method. The structural stability, which has been negatively affected by the absence of cobalt in the materials synthesized, is compensated by the addition of Al, and this objective is clearly achieved, particularly for the LR-NMA-2 material. The initial specific discharge capacity of LR-NMA-2 at 0.1C is 224.1 mAh/g, and the capacity retention after 100 cycles at 0.5C is 78%. Furthermore, the poor rate capability performance typically found in lithium-rich cathode materials is significantly improved in the LR-NMA-2 material due to its high c-axis lattice parameter, which is obtained by the presence of an appropriate amount of Al in the layered structure. The capacity of 120.6 mAh/g at a current density of 5C further demonstrates the superior rate capability performance of the Li_1.2Ni_0.18Mn_0.57Al_0.05O₂ material.