基于有机酸添加剂的全钒液流电池电解液稳定化调控机制及电化学行为

In order to improve the stability and electrochemical activity of the electrolyte by adding organic acid, the stability and electrochemical activity of the electrolyte were improved by adding the organic acid to the problem of improving the energy density and the running efficiency of the all vanadium redox flow battery. The basic research on the application of organic acid additives on the energy density and low efficiency of vanadium batteries. The effects of organic acid groups on the stability of vanadium ions were investigated. The effects of organic acid groups on the reaction mechanism and electrochemical behavior of vanadium ions were investigated by investigating the stability of organic acids. The electrochemical kinetics analysis of the electrolytic solution and the electrode was carried out to determine the combination of vanadium ion and organic acid in the electrolyte. The electrochemical effect of the vanadium ion and the organic acid was analyzed by the electrochemical kinetics analysis. The mechanism of the stability of the organic acid on the stability of the electrolyte and the process of the electrochemical reaction of the vanadium battery were proposed by comparing the stability and electrochemical performance test results. The scientific significance of the project is to improve the organic acid additives to optimize the electrolyte stability and electrochemical performance mechanism, in order to break the vanadium battery energy density lower technical limitations to provide a theoretical basis.

针对全钒液流电池的高浓度电解液稳定性和电化学性能较差，严重限制钒电池能量密度及运行效率提高的问题，项目通过添加有机酸改善电解液的稳定性及电化学活性，并就钒电池能量密度及效率低等问题进行有机酸添加剂应用的基础研究。通过查明有机酸添加剂基团影响钒电池电解液稳定性的变化规律，探究提高稳定性的有机酸种类、浓度及其作用机理，考察有机酸基团对钒离子的电极反应机理、电化学行为的影响，解析电极反应过程的极化行为及电池效率和能量衰减机制，并通过对电解液及电极进行检测，进行电化学动力学分析，确定电解液中钒离子与有机酸的结合形式，综合比对稳定性及电化学性能测试结果，提出有机酸对钒电池电解液稳定性调控和电化学反应过程的作用机理。项目的科学意义在于完善有机酸添加剂优化电解液稳定性和电化学性能的作用机理，为突破钒电池能量密度较低的技术局限提供理论基础。

项目查明了磺酸类有机酸添加剂基团影响钒电池电解液稳定性的变化规律，探究确定了提高稳定性的有机酸种类、浓度及其作用机理，考察了有机酸基团对钒离子的电极反应机理、电化学行为的影响，通过电解液性能检测和电化学动力学分析，确定了电解液中钒离子与有机酸的结合形式，提出了有机酸对钒电池电解液稳定性调控和电化学反应过程的作用机理。主要内容如下：.（1）开发出草酸还原制备钒电池电解液工艺。工艺参数为：n(H2C2O4):n(V2O5)为1:1、反应温度为90℃、反应时间为100 min、n(H2SO4):n(V2O5)为5:1，还原率和转化率分别达到93.35%和94.80%。草酸还原制备的电解液在电极反应中电化学极化降低，充电电压降低而放电电压升高，充放电容量增加，电池性能相较于标准电解液有一定提升。.（2）确定了钒电池电解液中水合钒离子的溶剂化结构。通过模拟计算及热力学研究确定了钒电池电解液中单体水合V2+、V3+、VO2+和VO2+的溶剂化结构分别为[V(6H2O)]2+、[V(6H2O)]3+、[VO(5H2O)]2+和[VO2(3H2O)]+。V(IV)和V(V)电解液中的[VO(5H2O)]2+和[VO2(3H2O)]+均不会发生自身缔合形成聚体结构而只以单体结构形式存在。.（3）优选出硫酸体系钒电池电解液添加剂。在硫酸体系钒电池电解液中，优选出最佳磺酸类添加剂为牛磺酸，在添加量为4mol%时，电解液荷电状态（SOC）可达95%，并在-10-40℃稳定运行且能量效率可达80%以上，能量密度可以达到27.98 Wh/L。牛磺酸与V(V)离子配位抑制了高温下V(V)离子的热沉淀，同时在传质传荷过程中起到载体和桥梁的作用，提高了正极电解液性能。.（4）确定了硫酸-盐酸体系电解液性能提升方法和机理。硫酸-盐酸体系中因引入氯离子而提高了V(V)、V(IV)和V(II)电解液稳定性，当硫酸盐浓度为2.0-3.0mol/L，氯离子浓度不超过6.4mol/L时，电解液钒浓度可达2.4 mol/L，稳定温度区间可达-20-50℃。氯化亚锡添加剂可进一步提升负极电解液电化学活性及可逆性，能量密度达到33.45Wh/L。