Continuous production of bio-inspired hierarchical core–pith–sheath fiber electrodes for high performance fiber-shaped batteries

Wet-spinning is an effective and scalable continuous manufacturing process for fiber electrodes. However, fiber electrodes prepared by traditional wet-spinning often suffer from low mechanical strength and poor ionic/electronic conductivity. Inspired by the radially hierarchical structure of plant stems, we developed a coaxial wet-spinning technique based on a drawing-extrusion mechanism. By regulating the Ca²⁺ concentration in the coagulation bath, a core-pith-sheath tri-layer architecture was constructed, which synergistically enhances mechanical strength and establishes efficient ionic transport pathways. Besides, a composite cathode consisting of MnO₂ nanosheets anchored on CNTs was synthesized, establishing a continuous electronic conducting network. The incorporation of dual conductive networks markedly enhanced the electrochemical and mechanical properties of the fiber electrodes. The fabricated fiber-shaped Zn-MnO₂ batteries (FZBs) delivered capacities of 343.5 mAh g^-1 at 0.1 A g^-1 and 144.7 mAh g^-1 at 5 A g^-1, respectively, along with excellent cycling stability—retaining 55.2% capacity after 5000 cycles at 5 A g^-1 (an average per-cycle decay of 0.01%). Moreover, after 100,000 bending cycles at 2 A g^-1, the capacity retention remained 74.9%. Furthermore, through tomography, electrochemical kinetics analysis, and ion-transport theoretical simulations, we elucidated the critical role of rapid ion migration within the porous pith layer in enabling high-performance fiber batteries. The universality of this mechanism was further verified in aqueous fiber-shaped lithium-ion batteries. This work provides a scalable multilayer structural design strategy and theoretical foundation for the development of advanced fiber-based energy storage devices.