Properties Study Of The Advanced Electrodes Fabricated By Electrospinning For All Vanadium Flow Battery

Under the "double carbon" context,energy storage has a new development opportunity.All-vanadium redox flow batteries（vanadium batteries for short）are expected to be the preferred solution for large-scale,long-term energy storage due to their high reliability,environmental friendliness,high safety and long life.The electrode is one of the key materials in a vanadium battery and is vital as the site and carrier for the electrochemical reaction to occur and for the completion of the charge and discharge of the battery.Commercial electrode materials,such as carbon and graphite felts,although low in price and chemically stable,are poorly electrochemically active,which severely limits the operating current density and power density of vanadium batteries,resulting in high initial system installation costs for energy storage.Electrospinning technology can prepare nano carbon fiber electrodes,which can effectively regulate the fine structure of the fibers,increase the specific surface area and electrochemical activity of the electrodes,and are widely used in vanadium batteries,capacitors and other energy storage applications.When applied to vanadium batteries,the conventional electrospun carbon nanofiber（PAN-based）electrodes have low electrochemical activity and wettability,and poor mass transfer performance,resulting in electrodes that can only be used at lower currents and energy densities.In this paper,two optimisation strategies to enhance the performance of polyacrylonitrile-based electrospun carbon nanofiber electrodes are proposed to prepare high performance vanadium battery carbon nanofiber electrode materials for the above problems,with the following two components:Firstly,in order to enhance the mass transfer performance of the electrode,a large porosity-porous channel structure electrode was designed and prepared by adding poly（methyl methacrylate）（PMMA）to the precursor solution,the diameter and pore size of the fibers could be controlled by regulating the PMMA content,and the optimal PMMA addition was 12%.This effectively increases the porosity of the carbon nanofibers and improves the mass transfer performance of the electrode.The electrode also has a high electrochemical active area,with an energy efficiency of 74.45%at 300 mA cm^-2 and 81.03%at 200 mA cm^-2.1200 stable charge and discharge runs indicate that the electrode has long-term cycling stability,and the comprehensive performance is better than that of commercial graphite felt electrodes,indicating that the electrode strategy with large pore and multi-channel structure has the low cost and high performance It is one of the potential ways to replace commercial electrodes in the future.Secondly,to further enhance the electrochemical activity of the electrode,metalorganic framework（MOF）UiO-66 was prepared and introduced into the vanadium battery electrode material,and a highly active carbon nanofiber electrode（PAN/UiO66）based on MOF was constructed by electrospinning technology.The electrode with a 1%introduction of UiO-66 exhibits an energy efficiency of 81.33%at 200 mA cm^-2 and good long-term cycling stability,with a comprehensive performance better than that of commercial graphite felt electrodes.This shows that the introduction of metal oxide based active species based on MOF provides a new technical idea for the development of new high performance vanadium battery electrode materials.