Influence of Mg²⁺ doping on the structure and electrochemical performances of layered LiNi_0.6Co_0.2-xMn_0.2Mg_xO₂ cathode materials

Introducing the Mg ion into host lattice is applied to improving the electrochemical performance of LiNi_0.6Co_0.2Mn_0.2O₂. The effect of Mg substitution for Co on the structure, morphology, electrochemical properties and Li⁺ diffusion coefficients are investigated in details. Rietveld refinement results reveal that Mg is incorporated into the bulk lattice, which results in reduced cation mixing and expand c-lattice parameter. All Mg-doped sample exhibit better cycle and rate performances, although the Mg substitution for Co led to decreasing a part of capacity. The Li diffusion coefficients obtained by galvanostatic intermittent titration technique (GITT) are increased with increases of Mg content. - Highlights: • Mg-doped sample exhibits better electrochemical performance. • The change of crystal structure by Mg doping are studied. • The Mg doping improves the lithium ion diffusion coefficient.