| As an important storage device in the field of energy storage,supercapacitor is widely used in electric vehicles,wearable electronic devices and high-power heavy machinery because of its ultra-high power density and fast charge/discharge advantages.However,with the progress of science and technology and the improvement of people's needs,supercapacitors have been difficult to meet the requirements of consumers,so it is of great practical significance to develop a supercapacitor with high performance.The electrochemical performance of supercapacitor mainly depends on its electrode materials.Transition metal hydroxide has great potential for development because of its ultra-high theoretical capacitance value.However,their conductivity is very poor,leading to the fact that the actual specific capacitance is far below their theoretical value.Transition metal sulfides are highly suitable for supercapacitor electrode materials because of their high conductivity and high electrochemical activity.One component often has more or less shortcomings,and it is difficult to achieve satisfactory results,both in structure and performance.Recently,a large number of reports have shown that the combination of multi-components can enhance the electrochemical performance of supercapacitors.Composite electrode materials can combine the advantages of each element to improve the electrochemical performance of supercapacitor.So,we take this idea as the breakthrough point,using the liquid phase reduction method and the hydrothermal method to make the multicomponent composite,and the structure of the materials were characterized.The electrochemical properties of the materials were tested and analyzed.The main idea of this paper is to use the nickel cobalt hydroxide as the starting point,through the design of electrode structure and the introduction of other pseudocapacitive materials,use of the synergistic effect of multi-component to improve the comprehensive performance of the supercapacitor,which play a valuable role to solve the current problems faced by the low capacitance capacitor,low energy density and poor conductivity and so on.The main research work includes the following parts:1.Study on the room temperature by liquid phase reduction method to control the synthesis of 3D sponge-like Co/Co(OH)2 nanocomposite materials,discuss the effect of reducing agent dosage on the morphology of the product.With the increase of the amount of reducing agent,the morphology of the material from the first nanometer particles gradually grow into 3D sponge-like nanocomposites.The synthesis process of the whole material is completed by self-assembly.The three-dimensional spongy lamellar structure of the material has been characterized,and there are many open holes on the surface of the material,so that it has a higher specific surface 63.5m2/g,which is more conducive to the infiltration of electrolyte and improves the electrochemical performance of materials.At the same time,the magnetic properties of the material were tested.The effect of metal Co on the electrochemical properties of the materials were preliminarily deduced by the comparison of the magnetic properties and the electrochemical properties of the materials.The electrochemistry test results show that the charge transfer resistance of the electrode materials was only Rct= 0.37 ?,which further validates the feasibility of our initial design.The electrochemical performance of the electrode material under the three electrode system: the specific capacitance of Co/Co(OH)2 electrode can be demonstrated in different current density of 1,2,5,10 and 20 Ag-1 were 1048,860,733,669 and 596 Fg-1 respectively,showing higher specific capacitance and rate performance.After 5000 cycles of charge and discharge at a current density of 10 Ag-1,the specific capacitance is maintained at 70.6% of the initial capacity.In addition,by assembling the Co/Co(OH)2//AC asymmetric capacitor to verify the practical application of the Co/Co(OH)2 electrode material,we show that the highest energy density is up to 36.6 Whkg-1 when the power density is0.43 KWkg-1 and the cycle performance of the asymmetrical capacitor is up to 78.1% at the high current density of 10 Ag-1.Therefore,Therefore,our work provides a green and low-cost method to prepare Co/Co(OH)2 nanocomposites as electrode materials for supercapacitors and show good electrochemical performance.2.The synthesis process of Ni-Co-S/Co(OH)2 has been investigated.A simple two-step process has been successfully applied to design and synthesize Ni-Co-S/Co(OH)2 nanocomposite with unique layered structure.This method is directly in situ vulcanization on the surface of the precursor to form a novel three-dimensional structure,so that the nickel cobalt sulfide is firmly combined with the hydroxide,and the three-dimensional open structure is beneficial to rapid diffusion of the electrolyte and provide rapid transmission of electronic channel.In the electrochemical test of three electrode system,the facilitation of nickel cobalt sulfide and cobalt hydroxide synergistic effect on supercapacitor electrochemical performance and the effect of different compound ratio on the were studied.The comparative analysis found that Ni-Co-S/Co(OH)2 nanocomposite has a larger specific capacitance than the precursors,and their specific capacitance is up to 1560.8 Fg-1 at the current density of 1 Ag-1 and has excellent multiplier performance(953.3 Fg-1 at 30 Ag-1)and cyclic stability(81.7% in 10 Ag-1),indicating that the multicomponent samples to enhance electrochemical properties.We also successfully assembled Ni1-Co2-S/Co(OH)2//AC solid state asymmetric capacitor,the capacitor current density of 1 Ag-1 was up to 137.2 Fg-1,and the cycle test of 10000 cycles under the current density of 3Ag-1 is kept at the initial 88%.In the 800 Wkg-1 power density show a high energy density 48.8 Whkg-1,and four red light-emitting diodes were lit successfully.The charge for 90 seconds can continue to light for ten minutes,which showed the practical application value of the materials.3.A novel C@Ni Mn-OH-Ni3S2/Ni foam nanocomposite electrode with layered structure was successfully prepared by three step hydrothermal method.The effect of each layer of the composite electrode was studied,and the design idea and feasibility of the nanocomposite electrode were also discussed.First,the thin layer of Ni3S2 was obtained by hydrolysis of thioacetamide on the surface of nickel foam.It was used as the substrate of the second step nickel manganese hydroxide for in-situ growth.Finally,the surface of the active substance was covered with a proper amount of carbon through the carbonization of glucose,and carbon on the surface of the active substance can be observed by TEM images.It can improve the circulation stability of electrode materials.The test of the three-electrode system showed that the cyclic stability of the electrode material increased from 82.4% to 92.1% after 3000 cycles.And at 1 Ag-1 current density,the specific capacitance is as high as 2512.7 Fg-1.Using this method,the synthesis of composite electrode can be directly used to test and use without further treatment,and save the steps to further prepare the electrode,effectively save time.This method of electrode preparation is also conducive to large-scale production of electrode materials.At the same time,we use the prepared composite electrode and activated carbon to assemble the C@Ni Mn-OH-Ni3S2/Ni foam//AC asymmetrical capacitor.Under the current density of 1.5 Ag-1,the specific capacity is up to 112.8 Fg-1.When the current density increases by 15 Ag-1,the specific capacitance can still reach 55.7 Fg-1,showing a nearly 50% high rate performance.The cyclic stability of 10000 cycles at the high current density of 10A/g is up to 94.6%.When the power density is 12.75Wkg-1,the C@Ni Mn-OH-Ni3S2/Ni foam//AC asymmetric capacitor device has the highest energy density of 45.3 Wh kg-1,and after a single charge,it can successfully light 4 red LEDs. |
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