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 NiS x nanoparticle-supported on porous carbon (NiS x @C) by crosslinking sodium alginate with nickel ions , followed by performing a high-temperature carbonization and low-temperature vulcanization process. The NiS@C and NiS 2 @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 NiS 2 @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 NiS x @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 (NiS 2 @C//AC device), respectively.