Achieving the optimal performance of VO@CoNC anchored on MX/CF through phosphorous-doped induced defects for the fiber-shaped solid-state Zn-ion battery

Aqueous zinc-ion batteries (ZIBs) are instrumental in advancing sustainable energy storage technologies, primarily due to their affordability and eco-friendliness. However, their further development into fiber-shaped ZIBs (FSZIBs) has been impeded by challenges related to appropriate 1D cathode materials coupled with low conductivity, sluggish kinetics, structural instability, low mass loading, inefficient ion pathways, and lack of flexibility. Herein, an integrated hybrid fiber-shaped cathode electrode (P_x–V₂O_5–x@CoNC@MX/CF) for the FSZIB is developed. The reported electrode design incorporates bimetallic metal–organic framework (MOF)-derived leaf-like CoNC structures, providing active sites and conductive connections for vanadium oxide-based nanofibril structure and the porous MXene-carbon fiber (MX/CF) substrate. Tuning the electronic structure, through phosphorus doping and creating oxygen vacancies, provides the resulting P_x–V₂O_5–x@CoNC@MX/CF electrode with good Zn²⁺ diffusion ability and stabilizes the vanadium oxide structure, to exhibit exceptional electrochemical performance as cathode for FSZIB. This strategy simultaneously enhances active material growth, prevents structural degradation, and facilitates a highly reversible de/intercalation process of Zn²⁺ ions. The assembled fiber-shaped solid-state ZIB (FSSZIB) based on P_x–V₂O_5–x@CoNC@MX/CF as the cathode and ZnNS@MX/CF as the anode demonstrates high energy density of 133 mWh/cm³ and power density of 425.2 mW/cm³. Moreover, the FSSZIB exhibits excellent cycling stability, with capacity retention of 79.8 % after 20,000 charge–discharge cycles, demonstrating its long-term durability.