In situ synthesis of polyaniline/carbon nanotube composites in a carbonized wood scaffold for high performance supercapacitors.

Carbonized and activated wood scraps are appealing scaffolds upon which to host active materials for supercapacitors, realizing the transformation of waste into a valuable device. However, the active material when loaded on the inner walls of the wood tracheids can be easily peeled off, resulting in poor cycling stability of the capacitor and low energy density. Here, we designed a novel composite electrode material for high-performance supercapacitors based on a polyaniline/carbon nanotube composite material with a core-shell structure synthesized in situ in a carbonized wood scaffold. Carbon nanotubes with excellent conductivity were first synthesized in situ on the inner walls of the tracheids via chemical vapor deposition, which were stably embedded in the wood tracheids to increase the specific surface area and active material loading active sites. Then, a layer of polyaniline was deposited on the outer surface of each carbon nanotube via electrochemical deposition to form a core-shell nanostructure. The composite material as a single electrode has high specific capacitances of 240.0 F cm ^-3 and 1019.5 F g ^-1 at 10 mA cm ^-2 . Finally, the asymmetric supercapacitor based on the carbon nanotubes/carbonized wood scaffold as the anode and polyaniline/carbon nanotubes/carbonized wood scaffold as the cathode exhibited a high energy density of 40.5 W h kg ^-1 at 162.5 W kg ^-1 and a high capacity retention rate of 93.74% after 10 000 charge and discharge cycles at a current density of 20 mA cm ^-2 .