One-step synthesis of nickel cobalt sulphides particles: tuning the composition for high performance supercapacitors

NiS2-CoS2 composites with different Ni and Co molar ratios for supercapacitors (SCs) were synthesized by one-step hydrothermal co-deposition method using cheap Na2S2O3 center dot 5H(2)O as sulfur source. With the increase of Ni content, the composites particle size increases gradually and the hollow sphere structure becomes more obvious. The electrochemical measurements demonstrate that these composites possess a high specific capacitance (C-m) performance, good rate capability and long cycle stability. To be specific, the Cm of Ni/Co/S-1 composite is the largest, up to 954.3 F g(-1) at 1 A g(-1), and as high as 309.5 F g(-1) even at large current density of 20 A g(-1). Furthermore, the Ni/Co/S-1 maintains 99.9% of its initial Cm after 1000 cycles at 5 A g(-1). Moreover, the asymmetric supercapacitors with Ni/Co/S-1 as positive electrode and active carbon as negative electrode are of prominent energy density of 29.3 W h(-1) kg(-1) at the power density of 0.7 kW kg(-1), and superior cycling stability of 99.1% initial value retention after 1000 cycles.