Organic Cross‐Linker Enabling a 3D Porous Skeleton–Supported Na₃V₂(PO₄)₃/Carbon Composite for High Power Sodium‐Ion Battery Cathode

Cathodes with high energy density and good structural stability are needed for sodium‐ion batteries (SIBs) to be applied in energy storage field. Herein, a 3D porous skeleton–supported Na 3 V 2 (PO 4 ) 3 /carbon composite (NVP@C‐3DPS) is synthesized via a simple sol–gel method by introducing an appropriate amount of citric acid as organic cross‐linker. The generated interlinking gel provides extensive support that orients the NVP crystal growth along the ductile carbon framework, directly exposing the active material to electrolyte. Field‐emission scanning electron microscopy results reveal that the hierarchical pores (macro and meso) are interconnected by the gel skeleton, with their thickness ranging from 50 to 300 nm. Thus, advantages are achieved, including a highly conductive continuous network, effective electrolyte contact surface areas, and short Na‐ion transfer distance. Moreover, the cross‐linking and porous property on the nanoscale gives very superior barrier‐free Na‐ion diffusion. Consequently, the NVP@C‐3DPS electrode exhibits excellent electrochemical performance, including superior high‐rate capacity (78 mA h g −1 at 192 C, approaching 76.9% of the initial capability of 98.6 mA h g −1 at 0.5 C), remarkable cycling stability (98.4% retention after 800 cycles at 1 C, 91.4% retention after 2000 cycles at 10 C), and outstanding high‐rate endurance (76.0% capacity retentions after 3000 cycles at 100 C).