Research On High-performance Supercapacitors: From The Preparation Of M-Ni-S (M=Co, Cu, Zn) Cathode Materials To The Assembly Of Devices

This thesis is mainly devoted to the design and the preparation of M-Ni-S?M=Co,Cu,Zn?positive electrode materials,as well as the assembly and research of high-performance asymmetric supercapacitors.The main research contents are as follows:1.Binary transition metal sulfide M-Ni-S?M=Cu,Zn,Co?nanosheets were designed and directly synthesized on the conductive Ni foam with the hydrothermal method.In the experiment,the nickel nitrate was used as the nickel source and TAA?thioacetamide?was used as the sulfur source.The morphologies,structures and the electrochemical performance of the binary transition metal sulfides after introducing different metal elements?like Cu,Zn,Co?were tested and studied.Finally,the M_1-xNi_xS electrode materials were selected to assemble the asymmetric supercapacitor.2.The P doped Co-Ni-S/N electrode materials were successfully synthesized by a simple and convenient hydrothermal method with the sodium hypophosphite as phosphorus source and Ni foam as the conductive substrate.After the incorporation of the phosphorus source,the specific surface areas and active sites of the Co-Ni-S/N nanostructure are greatly improved,which are beneficial to the improvement of electrochemical performance.The P doped Co-Ni-S/N electrode material possesses an ultra-high specific capacitance(3677.4 F g^-1 at 1 A g^-1)and excellent rate performance(63%retention at 20 A g^-1).At the same time,the retention of specific capacitance can still maintain 84%compared with the original specific capacitance after 10,000 cycles.Finally,an asymmetric supercapacitor?P doped Co-Ni-S//AC?with the P doped Co-Ni-S/N electrode material as the positive electrode material and activated carbon?AC?as the negative electrode material was assembled successfully.High energy density and power density(27.2 Wh kg^-1 at 0.87 kW kg^-1),excellent electrochemical stability of the as-assembled asymmetric supercapacitor have been achieved.3.The precursor of NiCo₂O₄,NiCo₂O₄ and three dimensional polyhedral nickel-cobalt-sulfur MOF structure?NiCo₂S₄?were gradually prepared by three steps procedure.The NiCo₂S₄ was then coated on the conductive Ni foam substrate,and their structures and electrochemical performance were studied.The NiCo₂S₄ electrode material we prepared was found to possess an ultra-high specific capacitance(1298 F g^-1 at 1 A g^-1)and excellent rate performance(82%at 20 A g^-1).In the meanwhile,the specific capacitance can still maintain 90.4%of the original specific capacitance after10,000 cycles.Finally,the asymmetric supercapacitor?NiCo₂S₄//AC?with the as-prepared NiCo₂S₄ electrode material as the positive electrode material and activated carbon?AC?as the negative electrode was assembled,which has high energy density and power density(27.2 Wh kg^-11 at 0.87 kW kg^-1),as well as the excellent electrochemical stability.