Carbon Nanosheets Grown with N‑Doped Carbon Nanotubes and Decorated with NiS2 Nanoparticles for High-Performance Supercapacitors

Carbon materials have been widely applied for supercapacitors due to their good conductivity and large surface area. However, supercapacitors using pure carbon materials as electrodes suffer from poor specific capacitance and low energy density. Herein, a ternary composite consisting of carbon nanosheets (CNS), nitrogen-doped carbon nanotubes (N-CNTs), and NiS2 nanoparticles is prepared through the synthesis strategy of polymer-foaming coupled with chemical vapor deposition growth of N-CNTs and subsequent sulfurization. In the heterogeneous structure of the as-prepared composite (NiS2/CNS@N-CNTs), the CNS play the role as the substrate for the growth of N-CNTs and construct entire conductive networks; the NiS2 nanoparticles offer extra pseudocapacitance. Thus, NiS2/CNS@N-CNTs display excellent performance in supercapacitors with a specific capacitance as high as 500 F g–1 at 0.5 A g–1. Moreover, the asymmetric supercapacitor shows an optimal energy density of 41.1 W h kg–1 and outstanding cycling stability of 96.1% capacity retention after 10,000 cycles at 5 A g–1, indicating its great potential for supercapacitors. The ternary heterostructure can inhibit the serious volume expansion of NiS2 in a charge–discharge process, boosting cycling stability. This strategy provides a pathway for the design and preparation of carbon-based heterostructures and composites for high-performance supercapacitors.