Regulating Anion Redox and Cation Migration to Enhance the Structural Stability of Li-Rich Layered Oxides.

Lithium-rich manganese-based layered oxide cathodes (LLOs) with oxygen redox reactions are considered to be potential candidates for the next generation of high-energy-density Li-ion batteries. However, the oxygen redox process that enables ultrahigh specific capacity usually leads to irreversible O2 release and cation migration, which induce structure degradation and severe capacity/voltage losses and thus limit the commercial application of LLOs. Herein, we successfully synthesized chlorine (Cl)-doped Co-free LLOs (Li1.2Mn0.53Ni0.27O1.976Cl0.024) and analyzed the effect of anion doping on oxygen redox and structure stability of LLOs. Cl doping has been proven to decrease the irreversible lattice oxygen loss to enhance the redox reversibility of oxygen and inhibit the transition-metal migration during cycles, which substantially enhances the capacity and voltage retention and improves the rate capability during cycling. This work provides new insights for the development of high-performance TM oxide cathode materials with reversible oxygen redox.