Synthesis of NiCo2S4 nanosheets coated on biomass activated carbon for high-performance asymmetric supercapacitors

Owing to its intrinsic characteristic, biomass activated carbon (AC) extracted from bagasse demonstrates high specific surface area and porous structure, which is widely regarded as a promising substrate to design AC@transition metal compound electrode material. Herein, NiCo 2 S 4 nanosheets uniformly grown on bagasse activated carbon (BAC@NiCo 2 S 4 ) is successfully prepared as composite electrode material for supercapacitors. Owing to the presence of porous BAC substrate with a large specific surface area of 1712.49 m 2  g −1 , the as-prepared BAC@NiCo 2 S 4 composite demonstrates hierarchical structure with a considerable specific surface area of 208.58 m 2  g −1 and good micro-mesoporous characteristic, thereby improving electrical performances with an impressive specific capacity of 2264 F g −1  at 1 A g −1 , and a good rate capability of 77.9 % retention from 1 to 20 A g −1 . Additionally, the as-assembled BAC@NiCo 2 S 4 //BAC asymmetric supercapacitor provides a high energy density of 64.9 W h kg −1  at 800.1 W kg −1 , and maintains 32.4 W h kg −1 when the power density is up to 8000.2 W kg −1 . The above results suggest that the BAC@NiCo 2 S 4 composite is a competitive electrode material in the field of energy storage.