Solar Trap‐Adsorption Photocathode for Highly Stable 2.4 V Dual‐Ion Solid‐State Iodine Batteries

Rechargeable aqueous iodine‐based electrochemical energy storage systems offer a cost‐effective alternative to conventional alkali metal batteries for grid‐scale applications. However, their practical deployment is hindered by sluggish iodine redox kinetics and the shuttle of polyiodides, which severely limit their lifespan. To address these challenges, a novel solid‐state organic||I 2 battery leveraging a Co 3 O 4 ‐TiO 2 heterojunction photocathode is developed. By integrating a photo‐assisted mechanism with an innovative device architecture, the system achieves accelerated iodine conversion kinetics, enhances iodide ion utilization, and enables a four‐electron redox pathway. Theoretical calculation combined with electrochemical analysis reveals that the photo‐assisted mechanism promotes electrostatic adsorption of polyiodides, accelerates interfacial charge transfer, and significantly improves iodine redox kinetics. As a result, the organic||I 2 battery delivers a high specific capacity of 1.36 mAh cm −2 , a discharge voltage of 2.4 V, and excellent cycle stability over 1000 cycles, retaining 80.9% of its capacity at a current density of 10 mA cm −2 . This photo‐enhanced battery exhibits strong competitiveness compared to previously reported iodine‐based batteries. The remarkable performance of this photo‐assisted prototype offers a sustainable and cost‐effective solution for next‐generation energy storage.