Preparation Of Nickel Sulfide Based Asymmetric Electrode Material And Its Performance Study

With the advantages of high power density,long cycle life and wide operating temperature range,supercapacitors are excellent energy storage and power supply devices at present.The electrode materials in supercapacitors play a crucial role in their performance,thus the development of electrode materials with excellent performance is a current hot topic.Nickel-based sulfides are widely used as capacitor electrode materials because of their superior theoretical specific capacity,high redox activity and fast electrical conductivity,but the actual specific capacitance of nickel-based sulfides alone as electrode materials is lower than their theoretical specific capacitance.The capacitive performance of the pseudocapacitor supercapacitor depends on the rapid electron transport and the redox reaction with rapid diffusion of external electrolyte ions.In view of this,this thesis successfully prepared a series of composites by constructing heterojunctions,intercalation vulcanization and increasing the specific surface area of the materials to accelerate the electron conduction and mass transfer processes as follows:（1）Cobalt and nickel containing precursor were prepared by one-step hydrothermal process,and Ni₉S₈/CoO heterojunction composite electrode materials were prepared by calcining the synthesized precursors in air atmosphere after reacting with sulfur gas（S）in a simple calcination and sulfidation process.The design of the heterostructure interface resulted in increased electron/charge mobility and enhanced redox activity.The specific capacitance reached 1773.8 F g^-1 in the three-electrode system for electrochemical performance tests.The specific capacity retention of the assembled asymmetric supercapacitor Ni₉S₈/CoO//AC ASC,at 3 A g^-1,was 89%and 79%after 10000 and 20000charge/discharge cycles,respectively,which showed that the electrode has good energy storage effect.（2）The composite electrode material NiS₂/Cu₈S₅-13 was prepared by using NiCl₂·6H₂O as the nickel source and thioacetamide as the sulfur source,adding ZIF-8and synthesizing the intermediate by hydrothermal reaction,followed by cation exchange.This method not only increased the surface area of the active material,but also weakened the aggregation of the copper-based material and improved the performance of the composite material.The NiS₂/Cu₈S₅-13 and activated carbon（AC）were assembled into an asymmetric capacitor,and the energy density of the device was 23 Wh kg^-1 at a power density of 7450.5 W kg^-1.After 10000 cycles of stability tests at 3 A g^-1,its specific capacity was 81%of the initial capacity,and after 20000 cycles of stability tests,it still After 20000 cycles,the specific capacity was still maintained at 75%of the initial capacity,showing its superior cycling stability.（3）The NiS/NiMn-LDH-4 electrode material was prepared by using hexamethyltetramine（HMT）as the base source,sodium dodecylbenzene sulfate（SDS）as the intercalator and sulfur source,adding Ni²⁺and Mn²⁺,and successfully preparing the intercalated NiMn-layered hydroxide by one-step hydrothermal and growing NiS on the surface.The electrode material was tested for 20000 cycles and the specific capacitance was 81%of the initial capacitance.The specific capacitance of the assembled asymmetric supercapacitor NiS/NiMn-LDH-4//AC was 146.37 F g^-1,and the specific capacitance was maintained at 76%of the initial capacitance after 20000 cycles of stability test at 3 A g^-1.