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.

Aqueous zinc-ion batteries (AZIBs) are considered as one of the most promising next-generation electrochemical energy storage systems owing to their high-power density, environmental benign, intrinsic safety, and the low cost of the abundant zinc resources. However, their further development is still plagued by the inferior electrochemical performance of cathode materials. Though extensive research has been conducted to investigate various cathode materials (including manganese oxides, vanadium oxides, Prussian blues analogy, and organic materials), design of high-performance cathodes with satisfying capacity and long-term cycling stability still faces great challenges. Oxygen-free vanadium-based compounds, owing to their better conductivity, larger interlayer spacing, lower ion diffusion barrier and higher theoretical specific capacity than those of vanadium oxides, have gained increasing attention recently. In this review, we summarize the recent development about the emerging oxygen-free vanadium-based compounds in AZIBs, emphasizing the methods to design electrode materials with desired structures, effective strategies to improve their electrochemical performance, and the fundamental electrochemical mechanisms. Finally, the current challenges and outlooks of oxygen-free vanadium-based compounds are proposed, providing a novel perspective and useful guidance for the design of high-performance vanadium-based cathode materials for AZIBs.

Lithium sulfur (Li-S) batteries with high specific capacity and energy density can bring enormous opportunities for the next-generation energy storage systems. However, the severe dissolution and shuttle effect of lithium polysulfides (LiPSs) is still the key issue that seriously impedes the development of practical Li-S batteries. Here, polar Co₉S₈ inlaid carbon nanoboxes (Co₉S₈@C NBs) have been investigated as cathode host for high-performance Li-S batteries. In this integrated structure, Co₉S₈ nanocrystals not only provide strong chemisorptive capability for polar LiPSs, but also act as a catalyst to accelerate polysulfide redox reactions; while carbon nanobox with large inner space can offer enough space to relieve the volume expansion and physically confine LiPSs’ dissolution. As a result, the S/Co₉S₈@C NBs cathode exhibits high specific capacity at 1C and the capacity retention was ~ 83% after 400 cycles, corresponding to an average decay rate of only ~ 0.043% per cycle.