A robust hierarchical microcapsule for efficient supercapacitors exhibiting an ultrahigh current density of 300 A g−1. Issue 14 (13th March 2018) - Yang, Cheng
Abstract : A unique three dimensional (3D) hierarchical microcapsule structure (NiS x @NCV) has been put forward, which is realized by the ensemble of N-doped carbon vesicles encapsulating dual-NiS x (α-NiS/NiS2 ) nanoparticles via an in situ nanospace-confined pyrolysis strategy. Abstract : A unique three dimensional (3D) hierarchical microcapsule structure (NiS x @NCV) has been put forward, which is realized by the ensemble of N-doped carbon vesicles encapsulating dual-NiS x (α-NiS/NiS2 ) nanoparticles via an in situ nanospace-confined pyrolysis strategy. The NiS x @NCV shows a high pseudocapacitance of 1600 F g −1 at 1 A g −1 and impressive rate performance (a capacitance retention ratio of 84.5%, from 1 to 25 A g −1 ). Benefiting from this intriguing configuration, a kind of high performance asymmetric supercapacitor (ASCs) has been fabricated, using 3D NiS x @NCV microcapsules and nanoporous carbon (NPC) as positive and negative electrodes, respectively. Remarkably, the fabricated ASCs achieve a capability of 135.06 F g −1 at 1 A g −1 and exhibit an outstanding rate capability at 32 A g −1 . More importantly, a high capacitance retention ratio of 87% is still achieved even at current densities from 32 to 300 A g −1, which exhibits well the ultrahigh rate performance of the NiS x @NCV//NPC ASCs. In addition, the NiS x @NCV//NPC ASCs deliver an attractive energy density of 48.02 W h kg −1 at a power density of 800 W kg −1, and still maintain 30 W h kg −1 even at an ultrahigh power density of 240 kW kg −1 . This is attributed to the rich redox reaction and interface effect of dual-NiS x nanoparticles, abundant active sites and high electrical conductivity from N-doped carbon vesicles.