Understanding the Role of Dopant Metal Atoms on the Structural and Electronic Properties of Lithium-Rich LiNiMnO Cathode Material for Lithium-Ion Batteries.

Improving the stability of lithium-rich cathode materials is important in refining the overall performance of lithium-ion batteries. Here, we have proposed doping of different metal atoms such as K, Ca, Cd, and Al in different sites of LiNiMnO, and we have investigated their structural and electronic properties using first-principles calculations. We found that the Ni ions in the pristine LiNiMnO structure maintained the +3 oxidation state for a longer time and resulted in the structural deformation during the long cycling process. Whereas, the Ni ions in the Cd-, K-, and Ca-doped LiNiMnO structure are in the +3 oxidation state for a very short time, compared to the pristine system. Our density functional theory (DFT) results show that the doping of the Cd ion in the Ni site of LiNiMnO is the most suitable one, because it inhibits structural change, decreases the formation energy, and suppresses the Jahn-Teller distortion, compared with the pristine system and other dopant atoms. This theoretical study gives new insight about doping strategy and will help in improving the electrochemical performance of Li-rich cathode materials.