Effect of Mg²⁺ doping on the structural, thermal, and electrochemical properties of LiNi_0.8Co_0.16Mg _0.04O₂

LiNi_0.8Co_0.16Mg_0.04O₂ layered oxide samples were synthesized by a chemical route that led to a crystalline phase at a relatively low temperature and allowed the control of the homogeneity and the microstructural properties of the final compounds. The structural properties of the synthesized sample were investigated by performing XRD Rietveld refinement. The role of the doping metal (Mg²⁺) on the electrochemical characteristics of this layered oxide was investigated via its use as cathode material in a lithium cell and observation of its structural evolution upon cycling by in-situ energy dispersive X-ray diffraction (EDXD). The thermal stability of the delithiated Li_xNi_0.8Co _0.16Mg_0.04O₂ cathodes was evaluated using differential scanning calorimetry (DSC). The results demonstrate that the Mg²⁺ doping greatly reduces the unit cell volume change during cycling, because of a very limited variation of the c lattice parameter. This improved structural retention also reflects an improvement of the stability of the doped cathode in its fully charged state.