A Photo-Assisted Chargeable Aqueous Zinc-Iodine Battery

Solar energy is an abundant and renewable energy resource, but it must be captured and stored for practical application in view of the intermittency and low-energy density. The search for an effective solar energy storage system is highly required, yet remains a challenge. In this paper, we design a novel solar energy storage device by integrating a TiO₂ photo-electrode into an aqueous zinc-iodine battery (ZIB). During charging process under illumination, I⁻ in catholyte is oxidized to I₃ ⁻ by photo-excited holes from TiO₂ photo-electrode. Meanwhile, the photo-excited electrons transfer to the anode through the external circuit and reduce the Zn²⁺ into Zn. Due to the compensation of photo-voltage, an ultralow charging voltage of 0.56 V is achieved, much lower than the discharging voltage (1.2 V), resulting in 54 % input electric energy savings.