Supercapacitor Assembly And Performance Study Based On NiCo₂S₄ Nano Electrode Materials

Supercapacitor with advantages of long cycle life,high power density,environmental friendliness,fast charge and discharge speed,is a novel energy storage device,which has wide application prospects in electronic products,electric vehicles,aerospace and other fields.But lower energy density has become a key factor limiting its practical application.Electrode materials,as the core of supercapacitors,are closely related to the energy storage performance of supercapacitors.NiCo₂S₄,as a transition metal-based sulfide electrode material,has become a potential supercapacitor material with high theoretical specific capacity,abundant raw material sources,and low cost.However,the volume expansion during the cycling process and limited active sites make the electrochemical performance need to be further improved.Aiming at the above problems,this thesis prepares high-performance nickel-cobalt sulfide electrode materials from three aspects:construction and nanotube array,composite electrode materials with core-shell structure,and element doping.The main tasks are as follows:（1）NiCo₂S₄ nanotube array with uniform morphology and size was prepared by hydrothermal method.The microstructure and composition were studied by a series of characterization methods.The synthesized materials were used as electrodes in supercapacitors to study their electrochemical performance.At a current density of 1 A/g,its specific capacity is 556 C/g.After 6000 cycles,the electrode keeps 71.1%of its initial capacity.（2）NiCo₂S₄ nanowire arrays with core-shell structure were synthesized by controlling the content of Mn ions.The synthesized material is used as a supercapacitor electrode.After 6000cycles,the capacity retention is 78.95%.The asymmetric supercapacitor device with this electrode and activated carbon as positive and negative electrode,respectively,has an energy density of 8.80 mWh cm^-3 at a power density of 220.103 mW cm^-3.After 6000 cycles,the capacity retention rate was 83.93%.（3）First,a simple one-step solvothermal method was used to synthesize NiCo₂S₄nanoflowers,and then the phosphorus-doped NiCo₂S₄ nano-flower was obtained by phosphating reactions.The microstructure of the products was characterized,and their electrochemical properties were studied as well.At a current density of 1 A g^-1,it has a specific capacity of 1026 C g^-1.The capacity retention is 89%after 20,000 cycles.An asymmetric supercapacitor device with this electrode as a positive electrode and activated carbon as a negative electrode,respectively,delivers capacity retention of 96.3%after 10,000cycles.At a power density of 1355.37 W kg^-1,the device has a maximum energy density of131.40 Wh kg^-1.