Preparation Of Nickel Tungstate Based One-dimensional Nanocomposites And Study On The Properties Of Supercapacitors

With the increasingly serious problem of air pollution caused by the excessive use of global fossil fuels,the research on clean and efficient development and utilization and energy storage equipment is attracting people’s attention.Among various energy storage devices,supercapacitors have attracted much attention because of their high output density,high charge discharge rate,good cycle stability and environmental friendliness.Electrode materials have a significant effect on the performance of supercapacitors.The results show that there is an obvious correlation between the surface area,surface morphology,microstructure and energy storage characteristics of electrode materials.In this thesis,we successfully prepared one-dimensional nickel tungstate based nanofiber electrode by simple electrospinning,high-temperature calcination and phosphorus doping,and characterized and tested its electrochemical properties.The specific research contents include:（1）One dimensional NiWO₄ nanofibers were successfully prepared by electrospinning and high temperature calcination with ammonium metatungstate and nickel acetate as reactants.By adjusting the calcination temperature in the tubular furnace,we obtained a series of one-dimensional niwo4 nanofibers and named them NWO-450 NFs,NWO-500 NFs,NWO-520 NFs,NWO-560 NFs and NWO-600 NFs.The electrochemical test shows that under the three electrode system with current density of 1 A g^-1and 1 M KOH electrolyte,the specific capacitance of NWO-520 NFS electrode can reach 1195 F g^-1,which is significantly better than that of one-dimensional niwo4 nanofibers obtained at other calcination temperatures(416 F g^-1,285 F g^-1,701 F g^-1,394 F g^-1).Moreover,under the condition of current density of 8 A g^-1,after 5000times of cyclic constant current charge and discharge,the capacitance of NWO-520NFS electrode is still relatively stable,which can reach 87.6%,which shows that the sample has good cyclic stability.（2）The previously prepared one-dimensional NiWO₄nanofibers were placed in a tubular furnace for phosphating,and then phosphorus doped one-dimensional nickel tungstate nanofibers were obtained.According to the different NiWO₄nanofibers used,the obtained materials are named P-NWO-450 NFS,P-NWO-500 NFS,P-NWO-520NFS,P-NWO-560 NFS and P-NWO-600 NFS.The electrochemical performance of P-NWO-520 NFS was studied under 1 M KOH electrolyte and three electrode system.When the current density was 1 A g^-1,the specific capacitance of P-NWO-520 NFS reached 1246 F g^-1.Under the same test conditions,its capacitance was significantly better than that of other samples.When the current density is 8 A g^-1,the capacitance of p-nwo-520 NFS can still be maintained to 81.8%of the initial value after 5000 cycles of constant current cyclic charge and discharge test.The above results show that the introduction of phosphorus in the electrode material significantly improves the storage performance and cycle stability of one-dimensional NiWO₄ nanofiber motor materials.