LAUSR

Abstract Relatively high cost is one of the biggest challenges for supercapacitors. Cheap carbon material expanded graphite (EG) was chosen to synthesize Ni(OH) 2 /EG composite by a facile microwave-assisted heating method. The Ni(OH) 2 /EG composites demonstrates a specific capacitance of 1569 F g −1 at current density of 1 A g −1 and 1077 F g −1 at current density of 10 A g −1 , based on the total mass of Ni(OH) 2 /EG composite, conductive agent, and adhesive agent. The Ni(OH) 2 /EG composite exhibits not only high specific capacitance and rate capability, but also excellent cycling stability with 73% retention of initial specific capacitance after 1000 cycles at current density of 10 A g −1 . An asymmetric supercapacitor AC//Ni(OH) 2 /EG was assembled and it demonstrates a comparable capacitance of 86.4 F g −1 at current density of 0.5 A g −1 , an energy density of 37.7 Wh kg −1 at a power density of 490.9 W kg −1 , and 26.1 Wh kg −1 at a high power density of 10.1 kW kg −1 . After 1000 cycles at the current density of 5 A g −1 , the specific capacitance can retain 80.1%. Therefore, the Ni(OH) 2 /EG composite will pave a promising way for supercapacitor-powered buses.