Preparation Of Ni/Co-based Composite Electrodes And Its Application In Supercapacitors

Supercapacitors?SCs?have become a heated research due to their high power density,good cycle stability and environment-friendliness.However,supercapacitors are limited by their low energy density than lithium batteries and accumulators.At present,they are mostly used as auxiliary power source materials for batteries or lithium batteries to satisfy the emergency demand of high power.How to further improve the energy density of supercapacitors is an obstacle of research.As a key factor to improve the performance of supercapacitors,the design and preparation of a high-performance electrode material are crucial to improve the energy density of the device.Double layer electrode materials have high conductivity,high specific surface area,good cyclic stability and magnification performance,but low capacitance.Pseudo-capacitor materials have high capacitance but poor cyclic stability and rate capability.In order to improve the performance of electrode materials,one of the effective methods is to prepare composite electrode based on double layer and pseudo-capacitance materials.In this paper,carbon materials are used as the substrate and compounded with pseudo-capacitor materials.Three-dimensional,porous composite electrode with self-supporting structure are prepared and applied to supercapacitor through structural design and optimization.The contents of research are as follows:First of all,NiS nanoflowers have been engineered by hydrothermal method as a secondary supporting structure based on flexible carbon fiber.And then we can obtain vertically aligned NiCo2S4 nanosheets on NiS nanoflowers through electrodepositing method.The self-supporting multi-level structure can effectively prevent the stacking and agglomeration of nanosheets,and achieve the composite electrode with high specific capacitance,high specific surface area and good cycling stability.It is applied to the water system asymmetric supercapacitor.At the current density of 1 A g^-1,the specific capacitance of composite electrode is 2667 F g^-1.The capacitance remains at 91.8%after10,000 cycles when the current density is 10 A g^-1.It shows a good cycling stability.The energy density of the water system asymmetric supercapacitor can reach 47.29 Wh kg^-1.Second,the porous and self-supporting composite electrode was successfully synthesized by using graphene as substrate and CNT@NiCo2O4 as supporting structure through the method of filtration.On account to the multilayer structure,the composite film shows excellent mechanical property and bending performance.After100 bending times,the structure maintains integrity.Electrochemical tests show that the specific capacitance of the composite electrode is 257 F g^-1 at the current density of 1A g^-1.