Scalable, Light Rechargeable Energy Storage Based on Osmotic Effects and Photochemical Reactions in a Hair‐Thin Filament

Abstract Scalable high‐performance distributed energy management systems (DERMS) on one micron‐scale fiber pose significant challenges. Here, an ultrafine single filamentary iontronic power source (10 µm thickness) is presented that utilizes ion transport within graphene oxide (GO) nanoconfined channels and silver halide interfacial redox reactions to achieve impressive gravimetric power (884.95 W kg⁻¹) and energy densities (108.7 Wh kg⁻¹), alongside rapid photo‐recharging capabilities within seconds. The controlled ultrasonic spraying technique enables the seamless integration of stable GO channels on filaments, preserving the integrity of other active layers. Through a detailed investigation of ion dynamics, an electrochemical nanoconfined ion transport pathway is proposed, demonstrating the polarization resistance of the filament battery is stable over a certain length, facilitating scalability. These devices exhibit consistent performance across a wide temperature range and under various environmental conditions, maintaining stability after 10 000 bending cycles. The world's thinnest rechargeable filament battery, with a total diameter of ≈120 µm is reported, offering a promising solution for next‐generation smart textiles, microelectronic circuits, and wearable DERMS.