Acid Thermal Modification For Electrode Of All Vanadium Redox Flow Battery And Its Macroscopic Mass Transfer

As a new,environment-friendly and efficient energy storage device,all vanadium flow battery realizes the cyclic charge and discharge by lutual conversion of different valence vanadium ions in electrochemical reaction.Because of its high safety,large energy storage-scale,high efficiency and long life,it has a good application prospect in the field oflarge-scale energy storage and is one of the effective ways to solve energy and environmental problems.However,the low energy density of the battery restricts its promotion and application.In this paper,the acid thermal modified graphite felt elect:rode was used to improve the performance of the battery.The macroscopic simulation method analyzes the assembly of the battery,the optimization of the flow field structure and the selection of the electrode parameters.Based on a large number of domestic and foreign literatures on all vanadium redox flow battery,this paper summarized its development history,research status and application prospects,explained its working principle and key materials.The electrochemical basis of all vanadium redox flow battery was introduced.The relevant properties of the graphite felt electrode assembled battery after acid thermal modification treatment were tested,and the macroscopic mass transfer analysis was carried out by nunerical method.The specific research contents were as follows:In this paper,the volt-ampere,charge-discharge and AC impedance characteristics of all vanadium redox flow batteries were tested by treating graphite felt electrodes under different acid or thermal treatment conditions.Then,the cyclic voltammetric characteristics and SFJM of the graphite felt electrode under different treatment methods were compared and analyzed,and the eff-iciency of the battery was calculated.The results showecl that the treated graphite felt electrode could inprove the performance of the battery,reduce the resistance of the Faraday resistance and enhance the electrochemical reaction.Besides,the performance of the graphite felt electrode after acid-thermal mixing treatment was better than the others.It provided a certain reference for the performance optimization of graphite felt electrodes for all vanadium redox flow battery.In this paper,the elastic mechanic equations,Nernst-Planck equations,Butler-Volmer equations and Nernst equations were coupled with comsol software battery moudule.A three-dimensional all vanadium flow battery isotherlal steady-state numerical mode!which bases on solid mechanics,thermodynamics,kinetics,mass transfer and electrochemical theory was established.First of all,the feasibility and correctness of the model were proved by comparing the simulation results with the experimental results.Secondly,the stress,displacement and porosity distribution of the graphite felt electrode under the conditions of preload,flow field structure and electrode thickness were simulated.The vanadiul ion concentration distribution,electrolyte current density distribution,electrolyte potential and overpotential distribution were analyzed.The results showed that the porosity of the graphite felt electrode was not a fixed constant under different preloads,flow field structures and graphite felt electrode thicknesses.The variation of porosity leaded to the changes of concentration distribution of vanadium ions,electrolyte potential distribution and effective conductivity of the battery.It also had an effect on the electrolyte current density and overpotential distribution.The optimal preload of all vanadium redox flow battery was 1.8MPa,the best flow channel and ridge ratio was 1,the optimal thickness of electrode was 3mm.The paper will provide an important reference for all vanadium redox flow battery on assembly,flow field structure and electrode parameter selection.