Photo-driven rechargeable aqueous zinc batteries based on NiCo-layered double hydroxide nano composite cathodes

Photo-rechargeable batteries based on photocathodes that have the dual function of collecting and storing solar energy offer an efficient method for solar energy utilization. Herein, NiCo-layered double hydroxide/ZnIn₂S₄/carbon nanotubes (CZN), a heterostructure photocathode, has been synthesized by layer-by-layer growth for photo-driven rechargeable aqueous zinc batteries (photo-driven rechargeable AZBs). The proposed photocathode exhibits typical photoelectric properties and offers the following advantages: good photoresponse in the visible light range, energy level/potential matching between ZnIn₂S₄ and NiCo-layered double hydroxide, and the conductive network formed by carbon nanotubes to promote charge transfer. The photo-driven rechargeable AZBs can harvest solar energy and store charge simultaneously, showing enhanced energy storage capability under illumination. The discharge capacity reaches 274.8 mAh g^-1 with a high photo-conversion efficiency of 1.120 % at 8.0 A g^-1 (100 mW cm^-2, white light). In particular, the photo-driven rechargeable AZBs can be charged by light solely, achieving a discharge capacity of 116.3 mAh g^-1. This study shows that the novel design and synthesis of the heterostructure photocathode is crucial and significant to enhancing the practicality of solar energy.