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.