Regulating oxygen redox reactions in lithium-rich materials via an Al2O3-doped ZnO layer for enhanced stability and performance

Abstract

Lithium-rich materials (LRM), which hold promise as high-energy-density cathodes, face challenges due to irreversible oxygen evolution. This leads to rapid capacity decay and structural instability. In this work, a regulated oxygen redox reaction is achieved by constructing an ultrathin and uniform Al₂O₃-doped ZnO (AZO) layer on LRM (AZO–LRM). The AZO coating layer serves as a charge carrier layer that can generate an internal electric field, thereby suppressing the migration of anions. A space charge layer is formed at the interface between AZO and LRM due to electron transfer, significantly reducing the non-bonding orbital energy and restraining oxidation of surface oxygen in LRM. Benefiting from regulated oxygen redox, AZO–LRM shows reduced phase degradation and fewer side reactions, resulting in a thinner, improved cathode electrolyte interphase (CEI) and more complete layered structure, significantly enhancing Li-ion diffusion and reducing impedance. Consequently, AZO–LRM retains 91% of its capacity after 200 cycles and shows a 145 mA h g⁻¹ capacity at a 5C rate. This work provides a universal and low-cost solution to oxygen evolution in LRM, offering a promising approach to overcome practical application challenges and highlighting the potential of doped oxides in high-voltage cathode materials.