Nickel-cobalt double hydroxides microspheres with hollow interior and hedgehog-like exterior structures for supercapacitors

Nickel-cobalt double hydroxide microspheres (Ni-Co-DHM) have been synthesized by a facile and cost-effective in situ method. The obtained Ni-Co-DHM displays a three-dimensional architecture with hollow interior and hedgehog-like exterior structures. The unique architecture greatly improves the faradaic redox reaction and mass transfer. The Ni-Co-DHM electrode offers an excellent pseudocapacitance performance, including high specific capacitance and rate capability, good charge-discharge stability and long-term cycling life. Its maximum specific capacitance was found to be 2275.5 F g(-1) at current density of 1 A g(-1), which is more than 3-fold that of common nickel-cobalt double hydroxides and 2-fold that of the mechanical mixture of Co(OH)(2) and Ni(OH)(2) microspheres. The specific capacitance can remain at 1007.8 F g(-1) when the current density increases to 25 A g(-1). The capacitance can keep at least 92.9% at current density of 10 A g(-1) after 5000 cycles. Therefore, this work provides a promising approach for the design and synthesis of structure tunable materials with largely enhanced supercapacitor behavior, which can be potentially applied in energy storage/conversion devices.