Natural‐Inspired Ultra‐Flexible Lithium‐Ion Batteries With Fractal Fern Architecture for Extreme Bending and Long‐Lived Stability

ABSTRACT Flexible lithium‐ion batteries (FLIBs) have attracted great attention as the most promising power sources for wearable electronic devices. However, achieving tolerance to dynamic bending at small radius, adaptability under dynamic loads, and stable electrochemical performance are still key challenges in the design of flexible LIBs. Herein, inspired by the exceptional flexibility of fern plants during expansion and contraction, a novel segmented node deformation LIB with ultra‐flexibility and cycle stability is designed and fabricated. With the unique features, the battery can even withstand severe dynamic alternating bending stress with a radius as small as 10 mm, demonstrating excellent resistance to extreme bending. Combining finite element analysis (FEA) with experimental results, the concentrated stress is effectively dispersed via controllable nodal deformation. The battery thus exhibits ultra‐long cycle stability even under harsh conditions with a minimal bending radius of 10 mm and over 42 000 dynamic bending cycles. Furthermore, the fern‐like battery is seamlessly integrated into both the flexible LED screen and the worm‐like robot. Beyond providing stable power, it functioned as a load‐bearing, deformable component. This work pioneers a novel biomimetic approach to designing next‐generation flexible batteries that simultaneously achieve exceptional mechanical robustness and multifunctionality.