Simulation Analysis Of Three Failure Modes Of The Vanadium Redox Flow Battery

Electric energy is a necessary secondary energy for social development and human production.With the transition of the times,people's demand for electric energy is constantly increasing.However,the large-scale use of fossil energy has brought environmental pollution and energy exhaustion.Therefore,solar energy,wind energy and other renewable energy sources are increasingly taken seriously by countries.Renewable energy power generation has the characteristics of instability,discontinuity and uncontrollable,so it must be stored and released through energy conversion.Vanadium redox flow battery as one of the large-scale stored energy is characterized by high safety,long cycle life,small environmental load,and recyclable battery materials.It has been paid more and more attention and its technology is more and more mature,which has a good market prospect.In this paper,the failure modes of vanadium flow battery during development,production and operation were reviewed,and the failure reasons of most failure modes were pointed out.However,vanadium flow battery still has some unexplained failure,if the reasons can not be found,it will affect the stable operation of the battery,and cause a lot of cost waste.In this paper,three failure modes of vanadium flow battery were analyzed by means of finite element analysis.Excessive leakage current in the reactor was the fundamental cause of leakage in the reactor caused by electrolyte precipitation and crushing in the non-reaction area of the ion exchange membrane.Concentration polarization was an important reason for battery performance degradation and electrode burn out.On this basis,according to the simulation calculation,the improvement measures were put forward for the above three failure modes.For the leakage failure at the end plate,the method of adjusting the force distribution of the stack fastening spring and increasing the end plate thickness was proposed.Experiments showed that the maximum deformation decreased from 5.3 mm to 1.9 mm,which effectively reduced the leakage failure risk at the end plate of the stack and improved the operational reliability of the stack.In order to reduce the shunt current and prevent the electrolyte from precipitating,a control strategy was proposed to reduce the number of series cells(guaranteeing the total number of cells and the total power unchanged)and to cooperate with the discharge-shutdown.The simulation result showed that the shunt current in the branch channel of the electrode frame decreased from 0.2585A to 0.0865A,and the temperature of the electrolyte decreased from 120?to 40.2?.Combined with the experimental verification,the precipitation of invaluable vanadium ions was effectively prevented,the risk of leakage failure of the stack was reduced,and the operational reliability of the stack was improved.For electrode burn out failure,a new electrode frame structure was proposed,which effectively reduced the dead zone of electrolyte and improved the reliability of stack operation.The simulation result showed that the new electrode frame can effectively reduce the area of electrolyte low velocity region and concentration polarization.On this basis,through the calculation of simulation,this paper has proposed a new type of battery with short flow field structure,which can effectively reduce concentration polarization of the battery.It was verified by the prototype that when the current density was 110mA/cm~2,the energy efficiency of the battery increased by 3%and the electrolyte utilization increased by9%.Through 3000 cycles lifetime test,the battery structure showed characteristics of stable performance and high reliability.