Wood-derived scaffolds decorating with nickel cobalt phosphate nanosheets and carbon nanotubes used as monolithic electrodes for assembling high-performance asymmetric supercapacitor

Abstract

Lightweight carbonized wood (CW) loaded with pseudocapacitive materials has demonstrated excellent energy density. However, the direct loading of active materials usually results in poor rate performance and cycling stability. Herein, we fabricated a CW electrode with high loading of active materials and conductivity through chemical vapor deposition (CVD) and electrodeposition to sequentially incorporate carbon nanotubes (CNTs) and nickel–cobalt phosphate (NiCo-P) nanosheets. This integrated NiCo-P/CNT/CW electrode exhibited a promising areal capacitance of 11.2F cm−2 at a current density of 10 mA cm−2, and a notable capacitance retention rate of 86.6 % at 60 mA cm−2. The asymmetric supercapacitor (ASC) device assembled with the prepared electrode as anode and the self-activated carbonized wood (SCW) electrode as cathode delivers outstanding energy density of 5.74 mWh cm−3 (12.1 Wh kg−1) at power density of 18.75 mW cm−3 (39.5 W kg−1) while maintaining a high capacitance retention of 92.4 % after 10,000 charge–discharge cycles. This work provides an advanced approach for constructing supercapacitors with remarkable energy density and rate performance from the natural wood derived electrodes.