Mechanisms Of Heat And Mass Transport And Performance Regulation Within The Porous Electrode And Flow Field Of Flow Battery

Large-scale energy storage technology is crucial to solving the intermittent and fluctuating nature of renewable energy generation.Zinc-bromine redox flow battery（ZBFB）is one of the most promising candidates for large-scale energy storage technology due to its high energy density,low cost,and long cycle life.ZBFB achieves the interconversion of electrical and chemical energy through reversible redox reactions of active species in the electrode.Therefore,it is necessary to investigate the influence of operational parameters on the redox reactions of ZBFB and to further improve the battery performance by optimizing the parameters.However,the effects of operational parameters on battery performance still need to be clarified,and numerical simulation studies of ZBFB are limited.In contrast,a comprehensive understanding of the influence mechanisms behind the structural design and operational parameters is a prerequisite for improving battery performance,and numerical modeling is a more economical and effective method.Based on this,this paper adopts a combination of numerical modeling and genetic algorithm optimization to investigate two significant issues:the influence of operational parameters on the ZBFB performance and to further improve the battery performance by optimizing the parameters.First,a 2D transient model of ZBFB is developed in this paper to reveal the effects of electrolyte flow rate,electrode thickness,and electrode porosity on battery performance.It was found that a higher positive electrolyte flow rate can improve battery performance by increasing the reactants utilization;however,increasing the electrode thickness or porosity causes a larger overpotential,thus deteriorating battery performance.Based on these findings,the battery performance is further improved by coupling a genetic algorithm to the model to seek optimality in the operational parameters.The results show that at a current density of 20 mA cm^-2,the optimal combination of 50 ml min-^-1 positive electrolyte flow rate,5 mm electrode thickness and 0.5 electrode porosity achieves an energy efficiency of 79.42%;at a current density of 40 mA cm-^-1,the optimal combination of 50 ml min-^-1 positive electrolyte flow rate,3 mm electrode thickness and 0.5 electrode porosity achieves an energy efficiency of 75.82%.This work is helpful to understand the energy storage characteristics and highperformance design of ZBFB operating at various conditions.