Self-supported and hierarchically porous activated carbon nanotube/carbonized wood electrodes for high-performance solid-state supercapacitors

• High-performance solid-state supercapacitor is fabricated with wood-derived carbon electrodes with low tortuosity and hierarchically porous structure. • The hydrophilic and conductive electrode exhibits ultrahigh specific surface area, superior capacitance, and excellent cyclic stability. • The solid-state symmetric supercapacitor shows a power density of 15.7 mW cm −2 and an energy density of 1.1 mWh cm −2 . Though the low tortuosity and the vertically aligned porous channels of wood-derived carbon can facilitate the electrolyte permeation and charge transport, pristine wood-derived carbon electrodes usually deliver poor electrochemical performances. Herein, high-performance solid-state supercapacitors with high areal capacitance and excellent cycling stability are fabricated with self-supported fir wood-derived carbon electrodes with low tortuosity and hierarchically porous structure. Carbon nanotubes are introduced to provide large specific surface area, continues electron transport, and excellent chemical stability. Importantly, the hierarchically porous channels with low tortuosity and high porosity are constructed by incorporating the vertically aligned macro-channels from fir wood-derived carbon and the massive meso- and micro-channels created by KOH activation, which are beneficial for diffusion of ions. The hydrophilic and conductive activated carbon nanotube/wood carbon electrode exhibits an ultrahigh specific surface area of 1646.6 m 2 g −1 , a superior capacitance of 24.0 F cm −2 (493.7 F g −1 ) at 1 mA cm −2 , and an excellent cycling stability with a capacitance retention of 98% after 10,000 cycles at 100 mA cm −2 . Furthermore, the assembled solid-state symmetric supercapacitor possesses a highest power density of 15.7 mW cm −2 and a maximum energy density of 1.1 mWh cm −2 .