Cobalt-free nickel-rich cathode materials based on Al/Mg co-doping of LiNiO 2 for lithium ion battery.

To develop Co-free LiNiO-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 LiNiAlMgO materials are synthesized by the solid-solid interface elemental interdiffusion strategy. It is elucidated that the Mg and Al 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 Mg ions may induce more Ni ions formed in the transition metal slabs, which would have great impact on the electrochemical performance of the materials. The LiNiAlMgO materials with optimized Mg/Al co-doping exhibit much better electrochemical performance than the pristine LiNiO and Al-doped LiNiO 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.