Defective Zn1-xCuxS nanosheet as efficient and durable cathode catalyst for photo-assisted Li-O2 batteries

Abstract

The introduction of light energy in lithium-oxygen batteries is seen as a promising strategy. However, the limited absorption of light by the photoelectrode and the rapid recombination of photo-generated electron-hole pairs are knotty problems. Herein, dual-defect engineering is applied for preparation of Zn_1-xCu_xS cathode catalyst for photo-assisted Li-O₂ batteries, in which Zn vacancy energy level promotes photon absorption, while the Cu doping facilitates the separation of carrier pairs. As a consequence, Zn_1-xCu_xS cathode exhibits great stability up to 163 cycles under illumination at 200 mA g⁻¹ with a fixed specific capacity of 600mAh g⁻¹, far exceed 46 cycles in darkness. Moreover, discharge product under illumination is film-like and fully decomposed during charging, while discharge product without illumination displays plate-like structure with restricted contact with cathode surface. This is attributed to defect-induced changes in the band structure and adsorption ability within cathode catalyst, which is confirmed via theoretical calculation. The strategy of dual-defect engineering is an effective approach for optimizing utilization of light and tuning Li₂O₂ formation, which holds great prospects in development of high-performance photo-assisted Li-O₂ batteries.