Construction of cathode-free iron-ion batteries by one-step synthesized carbon nanodots using FeO(OH) deposition

The development of high-performance and cost-effective battery technologies is crucial for storing and utilizing intermittent renewable energy. Aqueous iron-ion batteries (AIBs) constructed using low-cost iron salts hold promise in energy storage strategies but are constrained by the complex design and construction of cathode materials. Here, we report a one-step synthesis of carbon nanodots as conductive substrates for cathode-free aqueous iron-ion batteries, enabling the efficient deposition of hydroxyl iron oxide and enhanced ion storage. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman analyses confirm the effective deposition of hydroxyl iron oxide, ensuring the achievement of a maximum capacity of 0.43 mAh cm −2 . The designed cathode-free aqueous iron-ion battery demonstrates a long cycling life of up to 2000 cycles, representing a new direction for the development of aqueous iron-ion batteries.