ABSTRACT Activated carbon (AC) based supercapacitors (SCs) are known to suffer from low capacitance and poor rate capability due to their electrical double‐layer capacitance (EDLC) behavior. Herein, a nickel‐coated AC (Ni/AC) composite is reported to overcome the limitation of conventional EDLC properties of the AC materials. The composite with 30 min of Ni‐coating time (Ni/AC 30 ) demonstrates the best performance and exhibits a much higher specific capacitance (597 F g −1 ) than AC (85.7 F g −1 ) at 1 A g −1 current density in a three‐electrode cell configuration. Even at a higher current density of 20 A g −1 , the Ni/AC 30 still exhibits a capacitance as high as 342 F g −1 compared to only 34 F g −1 by AC, suggesting its excellent rate capability. Furthermore, the Ni/AC 30 electrode achieves an energy density of 10.1 Wh kg −1 at a power density of 173.9 W kg −1 , much higher than 1.4 Wh kg −1 at 174 W kg −1 by AC. In addition, the Ni/AC 30 electrode can smoothly be cycled over 10,000 charge/discharge cycles at 10 A g −1 . The Ni/AC 30 also exhibits extraordinary performance in a symmetric SC device and delivers an impressive specific capacitance of 228 F g −1 , suggesting its strong potential for practical applications.
Roshni et al. (Sun,) studied this question.