Stydy On The Preparation And Performance Of Nickel-cobalt-based Composites

Supercapacitors have great advantages such as excellent energy density and power density,high-current charging and discharging characteristics,and long working life.As an emerging energy storage device,they have been widely used.The electrode materials are the most important part of supercapacitors.Therefore,Ni-Co-S composites have drawn wide attentions from researchers because of their high capacitance,better conductivity and better rate performance.In this study,the micro-impinging stream reactor(MISR)was combined with the hydrothermal method to prepare nickel cobalt sulphide composite materials.The main findings are as follows:(1)The NiCo2S4/rGO composite was successfully prepared by MISR,and the optimal process conditions were determined as:the pipe diameter was 0.4 mm,the ion ratio was 1:1.1,the rGO doping amount was 5.7 wt%.At 1 A g-1,the specific capacitance of 1591 F g-1 could be obtained.After 1000 cycles,80.9%of the initial specific capacitance could be maintained;increasing the charging current by 20 times,the capacity could reach 1288.9 F g-1,and the retention ratio was 79.6%.The NiCo2S4/rGO and activated carbon(AC)were chosen as cathode and anode,respectively,to assemble a supercapacitor.At 0.5 A g-1,the retention ratio of the capacitance was 83.8%after 1000 cycles.(2)The optimal process conditions for the preparation of NiCo2S4 composite using MISR combined with hydrothermal method were determined as:two-step hydrothermal method,premixing using a micro-impinging stream reactor,hydrothermal temperature of 180?,hydrothermal time of 6 h.Flowerlike structure of NiCo2S4 composites could be obtained under the optimal process conditions.At 1 A g-1,the specific capacitance of 1643.2 F g-1 could be obtained.After 1000 cycles,83.8%of the initial capacitance could be maintained,showing excellent cycling performance.(3)The optimal process conditions for preparing NiCo2S4 composite using MISR combined with in-situ growth wre determined as:micro-impinging stream reactor for premixing,hydrothermal temperature of 180?,hydrothermal time of 6 h.The highest specific capacitance of 1959.4 F g-1 could be reached under the current density of 1 A g-1,and the retention ratio of the capacitance was about 72.4%after 1000 cycles.