In‐Situ Study of Photo‐Rechargeable Aqueous Zinc‐Ion Batteries with the Bifunctional α‐MnO ₂ Photoelectrodes

Abstract Directly harvesting solar power without traditional solar cells represents an efficient solution to the current energy challenges. Photo‐rechargeable batteries (PRBs) are receiving intense interest as they eliminate the additional costs and energy losses associated with off‐grid power generation. Herein, photo‐rechargeable aqueous Zinc‐ion batteries (PRZIBs) are constructed, using α‐MnO ₂ nanowires as bifunctional photoelectrodes to reveal the complex photo‐electrochemical effects in MnO ₂ PRZIBs. Through a series of in situ characterizations under illumination, the advantages of intrinsic light effects in α‐MnO ₂ based PRZIBs are elucidated from three aspects: (1) inhibition of Jahn‐Teller distortion via strengthened hydrogen bonding within α‐MnO ₂ , (2) suppression of Mn ²⁺ dissolution through the “protective layers” formed by photo‐promoted Zn ²⁺ /H ⁺ co‐intercalation, and (3) acceleration of Zn ²⁺ desolvation in the electrolyte enabled by abundant photogenerated holes. The PRZIBs with α‐MnO ₂ photoelectrodes demonstrate a specific discharge capacity of 308.1 mAh g ⁻¹ under illumination (1 sun), along with excellent cycling stability and high energy conversion efficiency of 0.68% (by photocharging only). In addition, the interdigital micro‐PRZIBs successfully power wearable sensors, demonstrating practical applicability. This work provides valuable insights into the time‐resolved reaction mechanisms in PRZIBs, and opens new prospects for developing PRBs in wearable and portable devices, i.e. smart textiles and biosensors.