Regulating π-type interactions between O 2p and TM t2g orbitals via Ti doping and surface dielectric coatings for Li-rich cathodes†

Abstract

The irreversible anionic redox reaction and oxygen release of Li-rich layered oxide cathodes seriously hinder their commercial application. Here, a synergistic modification strategy of surface dielectric coating (TiNb₂O₇) and bulk phase Ti doping is proposed in this paper. TiNb₂O₇, as a dielectric oxide, can generate a reversed electric field during charging to block the migration path of anions inside the material. In addition, the unique three-dimensional Li⁺ diffusion channels of TiNb₂O₇ can improve the lithium-ion diffusion kinetics. The results show that the synergistic modification strategy fundamentally inhibits oxygen loss and enhances the reversibility of anion redox, while constructing a uniform and stable CEI interface. The co-modification strategy effectively improves the electrochemical performance of the materials. The modified sample can maintain a high capacity of 175.1 mA h g⁻¹ after 500 cycles at 1 C. This work provides new insights to improve the oxygen loss problem of Li-rich layered oxide cathodes.