Design Of Electrode Materials For Hybrid Supercapacitors And Research On Its Electrochemical Performance

With the rapid development of society in the past few decades,the energy crisis has attracted great attention.The design and development of green sustainable energy and advanced energy storage equipments have attracted widespread scientific attention.The performance of supercapacitors is between that of chemical batteries and traditional capacitors,and can provide high power density,long cycle life and high reliability.However,due to its low energy density and narrow window voltage,the development of supercapacitors has been greatly restricted.Therefore,in this work we have conducted a series of experiments toward these issues.The specific research contents are as follows:(1)Using biomass ginkgo shell as a carbon source,a porous network porous carbon material(GSPC)was successfully synthesized by the KOH activation method.Its porous structure was used to form a higher specific surface area to increase its specific capacitance.At a current density of 0.5 A·g^-1,the specific capacitance can reach 345 F·g^-1.A symmetric capacitor device(SCD)is assembled bu using GSPC as electrodes.When the energy density of the assembled SCD is 13 Wh·kg^-1,the power density is 301 W·kg^-1.(2)A stable hollow tubular nanofibers HTNs was prepared by electrospinning,which have a good system of connecting nanoparticles and electronic conduction paths.By changing the content of PAN to change the concentration of the polymer solution and by controlling the flow rate of the syringe,we can regulate the diameter of the fiber.By adding 2-methylimidazole,ZIF-67 can be deposited on the as-prepared PAN@NiCo-HTNs nanofibers,and the hollow tubular nanofibers were formed after high-temperature annealing,exhibiting a relatively high specific surface area(450 m²g^-1).This composite shows an enhanced electrochemical performance.At a current density of 1 A g^-1,its specific capacitance is 672 F·g^-1.An asymmetric supercapacitor is assembled by using AN@NiCo-HTNs as positive electrode and activated carbon as negative electrode,which exhibts an energy density of 22.6 Wh·kg^-1at the power density of 699.9 W·kg^-1.(3)Using multiple hydrothermal methods,a uniformly distributed one-dimensional layered hollow Ni/Co layered double hydroxide nanocage was assembled on MnO₂nanotubes using ZIF-67 as a template.The size of ZIF-67 deposited on MnO₂nanotubes was controlled by changing the content of 2-methylimidazole,so as to form a uniform and stable morphology structure.The electrochemical test shows that MnO₂@NiCo-LDH has excellent electrochemical performance.The sample of MnO₂@NiCo-LDH-3 has a specific capacitance of 1455 F·g^-1at a current density of 1 A·g^-1.An asymmetric supercapacitor was assembled by using MnO₂@NiCo-LDH-3 as positive electrode and GSPC as negative electrode,which exhibits the power density of 800 W·kg^-1at the energy density of 40.5Wh·kg^-1.