Mixed-valence vanadium oxides based photocathodes for photo-rechargeable zinc-ion batteries with enhanced capacity and cycle life

Photo-rechargeable zinc-ion batteries (PRZIBs) integrate solar energy harvesting and storage in a single device through a dual-functional photocathode. While their compact size, simple structure, and low-cost make PRZIBs promising for self-powered solar electronics, practical deployment is hindered by the low capacity (120-300 mAh g -1 ) and poor cycling stability (<500 cycles). Herein, a mixed-valence V 6 O 13 nanoflower photocathode is designed to enhance the capacity and stability of PRZIBs. By photo-assisted charging, the as-fabricated PRZIBs achieve a discharge-specific capacity of 468.7 mAh g -1 and cycle life of over 1,500 cycles. It is found that irradiating the mixed-valence V 6 O 13 is able to induce proton insertion and enhance the capacity. At the same time, illumination could restrain the dissolution of V 6 O 13 cathode and formation of inactive zinc pyrovanadate phase, and thus suppress the interfacial degradation. Besides photo-assisted charging, the integrated device could also realize photo-charging under simulated sunlight. Without any external power source, five series-connected PRZIBs could drive a light emitting diode array by photo-charging. This work provides a viable strategy for high-performance PRZIBs in off-grid applications. A mixed-valence V 6 O 13 nanoflower-based photo-rechargeable zinc-ion battery (PRZIB) is developed, delivering a high capacity of 468.7 mAh g - ¹ and prolonged photo-assisted cycling stability. The performance is enabled by photo-induced, proton-dominated Zn 2+ /H + co-insertion, which mitigates lattice strain and suppresses the formation of the inactive ZVO phase. The device allows circuit-free charging to drive an LED array, thus offering a promising solution for sustainable, off-grid energy storage.