ABSTRACT Fiber‐based energy storage is integral to realizing smart textiles and soft electronics, where devices must deliver high power and adequate energy while tolerating repeated mechanical deformation. Metal‐ion hybrid capacitors—which pair a battery‐type faradaic electrode with a capacitive counterpart—offer a pathway to narrow the energy–power gap. While recent progress in metal‐ion chemistries and device architecture has improved electrochemical performance and compatibility with wearable formats, the field remains fragmented, and a unified understanding of these rapidly evolving developments is still lacking. Herein, a structured review is presented that first summarizes the broader landscape of fiber‐based energy storage systems, with emphasis on device architectures and fabrication strategies. It then outlines metal‐ion hybrid capacitors, highlighting their charge‐storage mechanisms, performance trade‐offs, and ion chemistries. On this basis, the review provides comprehensive knowledge of fiber‐based metal‐ion hybrid capacitors (FMHCs) across lithium‐, sodium‐, potassium‐, and zinc‐ion chemistries, discussing charge‐storage mechanisms, materials selection, device architectures, and fabrication routes. Finally, current challenges for practical deployment and future research directions are highlighted, providing a unified framework to guide innovative FMHC design toward practical, high‐performance wearable energy storage.
Sajedi‐Moghaddam et al. (Mon,) studied this question.