Synthesis of nickel sulfide-supported on porous carbon from a natural seaweed-derived polysaccharide for high-performance supercapacitors

Transition metal sulfides are regarded as an attractive electrode material because of their excellent metalloid characteristic and good electrical conductivity for supercapacitor applications. Herein, we successfully fabricated a hybrid material of NiSx nanoparticle-supported on porous carbon (NiSx@C) by crosslinking sodium alginate with nickel ions, followed by performing a high-temperature carbonization and low-temperature vulcanization process. The NiS@C and NiS2@C hybrids are obtained through changing the carbonization temperature and adjusting the mass of the S-containing precursor. Both of them are subsequently evaluated for their comparative electrochemical performances. The NiS@C electrode shows an excellent specific capacity of 372.6 mA h g(-1) at 0.5 A g(-1) with a mass loading of 3.5 mg cm(-2), and then retains 216.2 mA h g(-1) even if the current density adds up to 10 A g(-1). In contrast, the NiS2@C electrode delivers a specific capacity of 213.3 mA h g(-1) at 0.5 A g(-1) and an impressive capacity retention rate of 60.7% after 5000 charge-discharge cycles. Besides, the asymmetric supercapacitors composed of the NiSx@C hybrids and active carbon (AC) as the positive and negative electrodes deliver excellent energy densities of 58.7 W h kg(-1) at a power density of 406.4 W kg(-1) (NiS@C//AC device) and 44.4 W h kg(-1) at a power density of 397.6 W kg(-1) (NiS2@C//AC device), respectively. (c) 2020 Elsevier B.V. All rights reserved.

Automated summary

Transition metal sulfides, such as NiSx@C hybrids, were successfully synthesized through crosslinking sodium alginate with nickel ions and subsequent high-temperature carbonization and low-temperature vulcanization processes. The comparative electrochemical performances of NiS@C and NiS2@C electrodes were evaluated, with NiS@C showing higher specific capacity and better cycling stability. Additionally, asymmetric supercapacitors composed of the NiSx@C hybrids and active carbon demonstrated excellent energy densities at different power densities.