Understanding the Role of Dopant Metal Atoms on the Structural and Electronic Properties of Lithium-Rich Li1.2Ni0.2Mn0.6O2 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+, Ca2+, Cd2+, and Al3+ in different sites of Li1.2Ni0.2Mn0.6O2, and we have investigated their structural and electronic properties using first-principles calculations. We found that the Ni ions in the pristine Li1.2Ni0.2Mn0.6O2 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 Li1.2Ni0.2Mn0.6O2 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 Li1.2Ni0.2Mn0.6O2 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.