Molybdenum Disulfide–Zinc Oxide Photocathodes for Photo-Rechargeable Zinc-Ion Batteries

Systems for harvesting and storing solar energy have found practical applications ranging from solar farms to autonomous smart devices. Generally, these energy solutions consist of solar cells for light harvesting and rechargeable batteries to match the solar energy supply to consumption demands. Rather than having a separate energy harvesting and storing device, we report photo-rechargeable zinc-ion batteries (hν-ZIBs) using a photoactive cathode composed of layer-by-layer grown zinc oxide and molybdenum disulfide. These photocathodes are capable of harvesting solar energy and storing it in the same material and alleviate the need for solar cells or power converters. The proposed photocathodes achieve photoconversion efficiencies of ∼1.8% using a 455 nm light source and ∼0.2% of solar-conversion efficiencies. Light not only allows photocharging but also enhances the battery capacity from 245 to 340 mA h g^-1 (specific current of 100 mA g^-1 and 12 mW cm^-2 light intensity at 455 nm). Finally, the proposed hν-ZIBs also demonstrate a capacity retention of ∼82% over 200 cycles.