V-doped Co-free Li-rich layered oxide with enhanced oxygen redox reversibility for excellent voltage stability and high initial Coulombic efficiency

Li-rich Mn-based oxides (LRMOs) hold great promise as the next generation of lithium-ion battery cathode material due to their low cost and high capacity. Nonetheless, the practical application of LRMOs is impeded by their low initial Coulombic efficiency and rapid voltage decay. Herein, a V-doped layered-spinel coherent layer was constructed on the surface of Co-free LRMO through simple NH₄VO₃ treatment. The layered-spinel coherent layer with 3D ion channels serves the purpose of enhancing Li⁺ diffusion efficiency, mitigating surface-interface reactions, and suppressing irreversible oxygen release. Notably, V doping exerts a profound effect by significantly reducing the Bader charge of oxygen atoms, thereby impeding excessive oxidation of oxygen ions and further enhancing the stability of O-redox. Consequently, the treated sample exhibits a remarkable initial Coulombic efficiency of 91.6%, much surpassing that of the original sample (74.4%). Furthermore, the treated sample demonstrates an impressive capacity retention rate of 91.9% after 200 cycles, accompanied by minimal voltage decay of merely 0.47 mV per cycle. This straightforward treatment approach, which significantly improves the initial Coulombic efficiency, voltage stability, and capacity stability of LRMO cathode materials, carries profound significance for the development of high-energy lithium-ion batteries.