Expanded graphite supported Ni(OH)2 composites for high performance supercapacitors

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.