Effect of Mg Doping on the Performance of LiNi0.9Co0.1O2 Cathode for Lithium‐Ion Batteries

Abstract High‐nickel cathode materials are widely used in lithium‐ion batteries because of their advantages of high energy density and high safety. High‐nickel cathode materials need to further improve cycling stability because they are prone to structural changes and capacity degradation. This paper proposes a method to improve high‐nickel cathode materials by Mg doping. XRD proves that Mg‐doped high‐nickel materials still have R‐3 m spatial structural characteristics; Rietveld refinement confirms that the c‐axis gradually increases with the increase of Mg content. Combined with DFT calculations, the presence of Mg can inhibit structural collapse during charge and discharge, reduce Li/Ni antisite defects, improve the electronic conductivity of the material, and improve the cyclic stability of the material. The 0.6 mol % Mg‐doped sample has an initial discharge capacity of 233 mAh g−1 at 0.1 C in the range of 2.7–4.3 V, a capacity retention rate of 91.0 % after 50 cycles at 1 C, still retains 79.9 % after 100 cycles. The dQ/dV curves further indicate that the presence of Mg improves the structural stability of the material.