Mg/Fe site-specific dual-doping to boost the performance of cobalt-free nickle-rich layered oxide cathode for high-energy lithium-ion batteries

Abstract

Layer-type LiNi0.9Mn0.1O2 is promising to be the primary cathode material for lithium-ion batteries (LIBs) due to its excellent electrochemical performance. Unfortunately, the cathode with high nickel content suffers from severely detrimental structural transformation that causes rapid capacity attenuation. Herein, site-specific dual-doping with Fe and Mg ions is proposed to enhance the structural stability of LiNi0.9Mn0.1O2. The Fe3+ dopants are inserted into transition metal sites (3b) and can favorably provide additional redox potential to compensate for charge and enhance the reversibility of anionic redox. The Mg ions are doped into the Li sites (3a) and serve as O2−-Mg2+-O2− pillar to reinforce the electrostatic cohesion between the two adjacent transition-metal layers, which further suppress the cracking and the generation of harmful phase transitions, ultimately improving the cyclability. The theoretical calculations, including Bader charge and crystal orbital Hamilton populations (COHP) analyses, confirm that the doped Fe and Mg can form stable bonds with oxygen and the electrostatic repulsion of O2−-O2−can be effectively suppressed, which effectively mitigates oxygen anion loss at the high delithiation state. This dual-site doping strategy offers new avenues for understanding and regulating the crystalline oxygen redox and demonstrates significant potential for designing high-performance cobalt-free nickel-rich cathodes.