Electrochemical Capacitance Performance of Hybrid Supercapacitors Based on Ni ( OH ) 2 ∕ Carbon Nanotube Composites and Activated Carbon

Ni(OH) 2 /multiwalled carbon nanotube (MWNT) nanocomposites were synthesized by in situ loading Ni(OH) 2 on the carbon nanotubes in an alkaline solution. The effects of the added carbon nanotubes on the morphology and electrochemical capacitance of Ni(OH) 2 were investigated in various loaded amounts of Ni(OH) 2 . The MWNT substrates can reduce the aggregation of Ni(OH) 2 nanoparticles, inducing a good distribution of the nanosized Ni(OH) 2 particles on the cross-linked, netlike structure MWNTs. As a result, the rate capability and utilization of Ni(OH) 2 was greatly improved, and the composite electrode resistance was reduced. Under the optimal 70% mass load of Ni(OH) 2 in the composite, the capacity of the composite is 190 mAh/g at a current density of 0.4 A/g between 0 and 0.4 V vs SCE. The hybrid supercapacitor based on such Ni(OH) 2 /MWNT composite positive electrodes and activated carbon negative electrodes delivered a specific energy of 32 Wh/kg at a specific power of 1500 W/kg based on the total weight of the active electrode materials. It also exhibited good cycling performance and kept 90% of its initial capacity for over 2000 cycles.