Cation/Anion Co-Doping Enhances Oxygen Redox Reversibility and Structural Stability in Single-Crystal Li-Rich...

Li-rich Mn-based cathode materials (LRMs) are the most promising cathodes for the next-generation Lithium-ion batteries due to their high energy density. However, LRMs encounter formidable challenges such as voltage/capacity decay, mediocre rate capability, low cyclability, and substantial capacity loss at low temperatures. These challenges stem from irreversible oxygen release and subsequent structural deterioration. As energy storage devices are required to operate across a wide temperature range, enhancing the electrochemical performance of LRMs at both room and low temperatures is crucial. Herein, an approach of Al and F co-doping on novel single-crystal Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ is proposed to promote oxygen redox reversibility and enhance structural stability. Investigations into the oxygen redox couple and manganese electronic structure demonstrate that the Al and F co-doped electrode (LRMAF) retains a higher amount of lattice oxygen (O²⁻) and a greater amount of Mn⁴⁺ after cycling. As a result, LRMAF exhibits a high energy density of 1185 Wh kg^-1, an initial discharge capacity of 329 mAh g⁻¹ at 0.1C, achieves a rate performance of 155 mAh g⁻¹ at 5.0C and delivers 88% capacity retention after 100 cycles. Additionally, LRMAF exhibits excellent electrochemical performance at -20 °C. This enhancement is attributed to the novel single-crystal morphology combined with cation/anion co-doping.