Synthesis And Capacitive Performance Of Vanadium Nitride/Carbon As Electrode Materials

In this work,based on the precursor derived from polymers and combined with different vanadium source,various vanadium nitride/carbon composite electrode materials were prepared by the method of electrostatic spinning and liquid-liquid phase separation and applied for supercapacitors.?i?Vnadium nitride quantum dot/nitrogen-doped microporous carbon nanofibers?VNQD/CNFs?were developed by a method of combination of electrostatic spinning and high-temperature calcination under the mixture atmosphere of NH₃:N₂=3:2,in which V₂O₅ xerogel was used as spinning solution and mixed with PVP mechanically.The effects of heat treatment process and temperature on the microstructure and electrochemical performance were also investigated.It was found that the as-synthesized VNQD/CNFs with a diameter of about 200 nm,and exhibited outstanding capacitive properties with a maximum specific capacitance of 406.5 F/g at a current density of 0.5 A/g in 6 mol/L KOH aqueous electrolyte in the potential range from-0.2 to-1.2 V.?ii?Both asymmetric and symmetric carbon membranes were designed and fabricated through liquid-liquid phase separation and solvent evaporation using PAN as precursor,respectively.In contrast,asymmetric carbon membrane exhibited asymmetric porous structure with 3 D nanoscaled architecture,which facilitated ion transportation better by shortening diffusion pathways for charging and discharging process.Meanwhile,PEG was introduced into the casting solution to mediate the pore size to a rational range and enhance the surface area.When the ratio of PEG was 10 Wt.%,the carbon membrane showed the highest specific surface area and applicable hierarchical porous size.A maximum specific capacitance of 246.5 F/g was achieved at the current density of 0.5 A/g with good rate capability in an aqueous electrolyte 6.0 mol/L KOH within the potential range of-1.0 to0.0 V.?iii?Furthemore,we choose vanadyl acetylacetonate as vanadium element source added into PAN matrix.In the synthesized electrode membrane,vanadium nitride nanoparticles were uniformly distributed in the hierarchical porous carbon 3 D networks.Importantly,polymers of PAN,PEG,and PAN-b-PMMA-b-PAN were used to prepare the interpenetrating architecture and construct the oxide-contained functional group in materials surface.A maximum specific capacitance of 392.0 F/g was achieved at the current density of 0.5 A/g in an aqueous electrolyte 6.0 mol/L KOH within the potential range of-1.2 to 0 V.The negative electrode was further combined with Ni?OH?₂ as positive electrodes to assemble a hybrid supercapacitors device.Remarkably,it showed a high energy density of 43.0 to 32.3 Wh/kg at the power density in the range from 800 to 4000 W/kg,and a good cycling stability of 82.6%was obtained at a current density of 2.0 A/g after 8000 cycles.