Application Of Copper-based Compound Layered Double Hydroxide In Capacitor

With social and economic development,energy demand is growing,and the greenhouse gases released from the use of traditional fossil fuels have posed a serious threat to the environment and human health.Therefore,it is imperative to explore and apply clean and sustainable energy sources to meet the demand.As an emerging energy technology,supercapacitors are becoming the focus of research.Although the lack of energy density is the main drawback of supercapacitors in applications,the choice of electrode materials and composite structure design are feasible to improve the energy density.Copper-based compounds are promising for a wide range of applications in supercapacitor materials because of their many unique advantages,such as chemical stability,low cost,and environmental friendliness.In addition,layered double hydroxide,as a unique two-dimensional layered material,also has its special features,such as large specific surface area,high redox activity and tunable chemical composition.These advantages make double hydroxides also attract much attention in the field of supercapacitors.Therefore,in this thesis,different copper-based compounds and layered double hydroxides were investigated to the electrochemical performance of their composites in supercapacitors.Specifically,the following research work was done:1.Uniformly distributed arrays of Cu（OH）₂ nanorods were synthesized on copper foam（CF）by a simple in situ generation method.Immediately afterwards,Ni Fe-LDH nanosheets were uniformly grown and wrapped around Cu（OH）₂ rods under constant potential electrodeposition to form Cu（OH）₂@Ni Fe-LDH core-shell structured materials.Among them,the sample Cu（OH）₂@Ni Fe-LDH-3 obtained at an electrodeposition time of 200 s at-1 V has the most excellent electrochemical performance with a specific capacitance up to 4.139 F cm^-2(1478.2 F g^-1).When Cu（OH）₂@Ni Fe-LDH is used as the positive electrode material and activated carbon as the negative electrode material,asymmetric supercapacitors can be assembled with an energy density as high as 65.56 Wh kg^-1 at a power density of 750 W kg^-1.The excellent electrochemical performance mainly comes from the unique synergistic effect of Cu（OH）₂ and Ni Fe-LDH materials,which makes Cu（OH）₂@Ni Fe-LDH materials have great prospects for development in the field of supercapacitors.2.CuCo₂O₄ nanoneedle arrays were fabricated on nickel foam（NF）by hydrothermal and annealing treatment methods.As a bimetallic oxide,CuCo₂O₄ has a higher theoretical capacitance value than monometallic oxides（Cu O and Co₃O₄）.Next,Ni Mn-LDH nanosheets were loaded on CuCo₂O₄ nanoneedles using a further hydrothermal method to form CuCo₂O₄@Ni Mn-LDH core-shell structured materials.This structure greatly increased the specific surface area while narrowing the ion diffusion distance and improving the chemical reactivity.Among them,the CuCo₂O₄@Ni Mn-LDH-2 electrode with a hydrothermal time of 6 h at 90°C exhibited the most superior electrochemical performance with a capacitance of up to 2955.2F g^-1.When CuCo₂O₄@Ni Mn-LDH-2 and activated carbon materials are used as positive and negative materials to assemble asymmetric supercapacitors,the energy density can reach up to 62.93 Wh kg^-1 at 799.96 W kg^-1 power density.Therefore,the exploration of CuCo₂O₄@Ni Mn-LDH materials is of great significance to the future development of supercapacitors.