Fabrication And Capacitive Performance Of Vanadium Nitride/Nitrogen-Doped Carbon Based Nanocomposites

It is urgently needed to find a low-cost,eco-friendly and high-performance energy storage and conversion device to reduce the consumption of unrenewable energy and environmental pollution.Supercapacitors?SCs?,have been propelled to the forefront of the energy storage field due to their inherent merits,including high power density,fast charge and discharge,long cycle life and environment friendly,etc.Searching for a class of novel electrode materials with high energy and power density is still a challenge for the further development of SCs.Vanadium nitride?VN?,as a kind of typical metal nitride,has been considered as a novel electrode material for SCs in view of its high specific capacitance,electrical conductivity as well as a wide potential window.Nevertheless,the reaction of the oxide layer?VO_x?on the surface of VN with alkaline electrolyte always results in a poor cycling stability for the electrode material.In our work,nitrogen-doped carbon?NC?is utilized and combined with VN for further improvement of the specific capacitance and cycling stability of the electrode material.The main contents are as follows:???VN/NC nanocomposite composed of VN NPs and nitrogen-doped carbon?NC?thin layer covering on the surface of VN has been prepared via a facile template-free solvothermal method followed by annealing processes in N₂ and NH₃ atmosphere,the phase structure and electrochemical behavior of the VN/NC nanocomposite are also tested.Study reveals that the VN/NC composite with abundant mesopores leads to a more effective electrolyte penetration and rapid ion/electron transportation.Moreover,a thin amorphous nitrogen-doped carbon layer on the surface of VN effectively inhibits the oxidation of VN during cycling in alkaline electrolyte,thus,the cycling stability of the electrode material is improved.???Vanadium nitride/N-doped carbon?VN/NC?nanocomposites have been prepared from the eco-friendly nitrogen source of g-C₃N₄ by a facile one-step annealing process,the phase structure and electrochemical properties of the composites have been studied.The results show that the VN/NC composites exhibit a higher cycling stability and specific capacitance than that of the commercial VN NPs when the NC nanosheets is used as the support skeleton for VN NPs.? ??Ni/VN/NC nanocomposites have been synthesized with the nitrogen source of melamine by a facile one-step method.Ultra-mall Ni NPs and VN NPs are embedded into nitrogen-doped carbon?NC?nanosheets,the resulting Ni/VN/NC composites are used as negative electrode materials for SCs.The results show that as a supporting skeleton,NC nanosheets can effectively prevent VN and Ni NPs from aggregating and enhance the cycling stability of the nanocomposites.The Ni/VN/NC electrode materials show a good specific capacitance,conductivity and rate capability due to the excellent conductivity of Ni NPs and N-doped carbon nanosheets as well as the high specific capacitance of VN NPs.