Numerical Analysis Of Mechanical Failure And Mechanism Of Mechanical Effect On Electrochemistry Of Vanadium Battery

Flow battery is one of the most suitable electrochemical energy storage systems for large-scale energy storage at present.In practical application,it is usually connected by a large number of single battery stacks in series or in parallel.Each battery stack is composed of numerous components with different structures stacked and assembled tightly.This kind of stacking and assembling method and battery structure make the flow battery have some characteristics different from other batteries,for example,the leakage characteristics of battery stack caused by the improper stress distribution between components,the changing internal contact resistance of battery and variable reactive area of electrode caused by the different stacking tightness between key components.These show that the mechanical state of the components in the liquid flow battery will not only affect the mechanical performance and operation life of the battery,but also influence the electrochemical performance of the battery due to its special battery structure.Therefore,it is of great significance to study the mechanical failure and the mechanism of mechanical effect on electrochemistry of the flow battery.In this paper,the typical vanadium redox flow battery is taken as the research object.Through the establishment of three-dimensional mechanical model and electrochemical model,combined with experimental analysis,the mechanical and electrochemical characteristics of the flow battery are systematically studied,especially the influence mechanism of the mechanical state of the components in the battery on the mechanical failure,battery reliability and battery electrochemical performance.The study is helpful to optimize the structure design and assembly conditions of all vanadium redox flow battery,and it plays an important role in improving the mechanical performance,operation life and efficiency of the battery.The mechanical failure and the mechanism of mechanical effect on electrochemistry of all vanadium redox flow battery is studied as follows:Firstly,a three-dimensional solid mechanical model of vanadium battery based on the generalized Hooke's law of linear elasticity is established.The mechanical experimental research which is difficult to carry out in large-scale energy storage battery is successfully transferred to a simple and easy numerical simulation analysis by using the finite element method,which provides an effective research method for the mechanical failure analysis of large-scale energy storage system.Then,aiming at the mechanical failure of battery,the stress distribution characteristics of the components in the battery under different design and assembly conditions are analyzed,and the material failure criterion is introduced to study the potential mechanical failure or damage of the components.The results show that the membrane,bipolar plate and flow frame are the components that are prone to mechanical failure in the battery;the structural design and clamping force of the battery are two important factors that affect the mechanical performance of the battery.Next,in order to evaluate the mechanical properties of the battery quantitatively,the concept of the mechanical failure probability of the battery stack is put forward,and the structure of the battery stack is optimized.The results show that the failure probability of the battery stack is closely related to the material,the design of the battery stack and the assembly force,and the design of adding thick plates in the middle of the battery stack can significantly reduce the mechanical failure probability.Finally,to study the mechanism of mechanical effect on electrochemistry,a three-dimensional electrochemical model of vanadium battery is established based on mass conservation and charge conservation.The mechanical model and electrochemical model of vanadium battery are coupled.The influence of assembly force of battery stack on electrochemical characteristics of the cell is analyzed comprehensively,with emphasis on electrode morphology,electrochemical mass transfer process and the change rule of polarization.Except for that,the comprehensive influence of assembly force on the mechanical failure probability and electrochemical performance of the battery are also optimized.The results show that with the increase of assembly force,the overall polarization of vanadium battery decreases,and high power density can be achieved under a certain assembly force.Considering the influence of the assembly force on the mechanical failure probability of the battery,the optimal assembly force is finally selected,which makes the battery have a lower mechanical failure probability while achieving high power density.