First-principles calculations to investigate the impact of fluorine doping on electrochemical properties of Li-rich Li 2 MnO 3 layered cathode materials.

Li-rich layered oxides are promising candidates for high-capacity Li-ion battery cathode materials. In this study, we employ first-principles calculations to investigate the effect of F doping on Li-rich Li 2 MnO 3 layered cathode materials. Our findings reveal that both Li 2 MnO 3 and Li 2 MnO 2.75 F 0.25 exhibit significant volume changes (greater than 10%) during deep delithiation, which could hinder the cycling of more Li ions from these two materials. For Li 2 MnO 3 , it is observed that oxygen ions lose electrons to compensate for charge during the delithiation process, leading to a relatively high voltage plateau. After F doping, oxidation occurs in both the cationic (Mn) and anionic (O) components, resulting in a lower voltage plateau at the beginning of the charge, which can be attributed to the oxidation of Mn 3+ to Mn 4+ . Additionally, F doping can somewhat suppress the release of oxygen in Li 2 MnO 3 , improving the stability of anionic oxidation. However, the increase of the activation barriers for Li diffusion can be observed after F doping, due to stronger electrostatic interactions between F - and Li + , which adversely affects the cycling kinetics of Li 2 MnO 2.75 F 0.25 . This study enhances our understanding of the impact of F doping in Li 2 MnO 3 based on theoretical calculations.