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 carbon nanotubes (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.