Stable Photo‐Rechargeable Al Battery for Enhancing Energy Utilization

Abstract Photovoltaic cells (PVs) are able to convert solar energy to electric energy, while energy storage devices are required to be equipped due to the fluctuations of sunlight. However, the electrical connection of PVs and energy storage devices leads to increased energy consumption, and thus energy storage ability and utilization efficiency are decreased. One of the solutions is to explore an integrated photoelectrochemical energy conversion‐storage device. Up to date, the integrated photo‐rechargeable Li‐ion batteries often suffer from unstable photo‐active materials and flammable electrolytes under illumination, with concerns in safety risks and limited lifetime. To address the critical issues, here a novel photo‐rechargeable aluminum battery (PRAB) is designed with safe ionic liquid electrolytes and stable polyaniline photo‐electrodes. The integrated PRAB presents stable operation with an enhanced reversible specific capacity ≈191% under illumination. Meanwhile, a simplified continuum model is established to provide rational guidance for designing electrode structures along with a charging/discharging strategy to meet the practical operation conditions. The as‐designed PRAB presents an energy‐saving efficiency ≈61.92% upon charging and an energy output increment ≈31.25% during discharging under illumination. The strategy of designing and fabricating stable and safe photo‐rechargeable non‐aqueous Al batteries highlights the pathway for substantially promoting the utilization efficiency of solar energy.