Enhancing the Supercapacitive Properties of Activated Carbon Through Controlled Nickel‐Coating

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.