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

摘要

NiS _(2) –CoS _(2) composites with different Ni and Co molar ratios for supercapacitors (SCs) were synthesized by one-step hydrothermal co-deposition method using cheap Na _(2) S _(2) O _(3) ·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 C _(m) 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 C _(m) 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.