Cobalt-free nickel-rich cathode materials based on Al/Mg co-doping of LiNiO₂ for lithium ion battery

To develop Co-free LiNiO₂-based layered cathode materials is crucial for meeting the demands of the lithium-ion batteries with high energy density, long cycling life, and low cost. Herein, the LiNi_1-x-yAl_xMg_yO₂ materials are synthesized by the solid-solid interface elemental interdiffusion strategy. It is elucidated that the Mg²⁺ and Al³⁺ ions are mainly doped in the Li slabs and transition metal slabs, respectively, leading to the alteration of the crystal lattice. Furthermore, the incorporation of the Mg²⁺ ions may induce more Ni²⁺ ions formed in the transition metal slabs, which would have great impact on the electrochemical performance of the materials. The LiNi_1-x-yAl_xMg_yO₂ materials with optimized Mg/Al co-doping exhibit much better electrochemical performance than the pristine LiNiO₂ and Al-doped LiNiO₂ materials, including cycling stability and rate capability. The in-situ XRD characterization and structural analysis show that stabilization of the crystal structure, preservation of the integrity of the secondary particles, and enlargement of the interlayer spacing by the Mg/Al co-doping are the main factors responsible for the superior performance of the materials. The Mg/Al co-doping strategy might be the promising approach for the design of the cobalt-free nickel-rich materials.