Design of gradient pore structure, high conductivity and superhydrophilicity to ensure high performance SiC nanowire supercapacitors under 0–60 °C

Design and optimization of electrode material structures are critical steps in the development of supercapacitors. This work presented a design strategy based on SiC nanowires (NWs) as supercapacitor electrode with gradient pore structure, superhydrophilicity, and enhanced conductivity. SiCNWs were in-situ fabricated on a carbon fabric substrate radially via chemical vapor deposition (CVD), constructing conical channels with gradient pore sizes that generate capillary forces and promote ion transport. An ultrathin pyrolytic carbon (PyC) shell (4.98 nm) was coated on the SiCNWs, to improve electrical conductivity without compromising pore structure or wettability. SiCNWs@PyC electrodes with a diameter of ∼0.93 μm exhibited excellent electrochemical performance from 0 to 60 °C. At 25 °C and a current density of 0.2 mA/cm², the areal capacitance of SiCNWs@PyC electrode was 32.48 mF/cm², representing 227.58% of the areal specific capacitance of pure SiCNWs. At 60 °C, the capacitance remained high at 28.09 mF/cm² under the same current density. The in-situ growth strategy and high mechanical stability of the material enabled the symmetric supercapacitor to maintain outstanding rate performance and cycling stability across a wide temperature range. The SiCNWs@PyC core-shell nanostructure is a promising supercapacitor electrode material, offering valuable insights for the development of next-generation energy storage devices.