Controlled oxidation of V2O5/VO2 hollow nanospheres as photocathodes for photo-rechargeable zinc ion batteries with an ultrahigh capacity enhancement

Abstract

Photo-charging batteries are emerging as a new battery technology for large-scale energy storage systems. However, their specific capacity, cycling stability, and light efficiency have reached a bottleneck due to low light-absorption capability, sluggish separation and migration of photoinduced charge carriers, and severe photocorrosion. Herein, hollow nanospheres composed of divanadium pentaoxide/vanadium dioxide (V₂O₅/VO₂) are constructed to broaden light harvesting and improve the redox activity of photo-rechargeable zinc ion batteries (ZIBs). Due to an in situ chemical reaction, V₂O₅ and VO₂ are intimately connected to form a V₂O₅/VO₂ heterojunction, thus facilitating the separation and migration of photoinduced charge carriers. As a result, this V₂O₅/VO₂ heterojunction demonstrated a maximum surface photovoltage (SPV) of 25.73 mV, resulting in an ultrahigh specific capacity of 785.6 mA h g⁻¹ at 200 mA g⁻¹ through a light-discharging process. This delivers a high light enhancement of 77.8% with a power conversion efficiency (PCE) of 4.3%. In addition, ZIBs show promising stability under light irradiation, where a high retention of 53.1% can be achieved even at high current density of 1000 mA g⁻¹ after 4000 cycles. This work has pushed forward ZIB technology into a green and sustainable path that can utilize solar energy to promote electrochemical energy storage.