全钒液流电池技术作为一种有效的、发展前景良好的大规模储能技术，以其快速响应、安全可靠、容量和功率可独立设计、长循环寿命等优点，受到了人们的广泛关注。但是由于全钒液流电池正极电解液中五价钒在高温下不稳定性这一现象，导致了全钒液流电池在工程放大和电堆设计过程中需要添加换热系统，进而导致了全钒液流电池成本的增加，限制了全钒液流电池技术的推广和应用。本论文以高浓度硫酸铁作为全钒液流电池正极电解液的添加剂，采用热稳定性实验、循环伏安法测试、电化学阻抗谱测试、粘度测试、电化学循环测试等方法，研究了不同浓度硫酸铁对电解液热稳定性、粘度、电化学活性以及电池循环等性能的影响。并采用拉曼光谱和核磁共振钒谱等方法尝试揭示硫酸铁稳定钒电解液的机理。研究结果表明硫酸铁的加入会极大地提高五价钒电解液的热稳定性，当五价钒电解液浓度在1.7mol/L左右时，控制硫酸铁的浓度在0.5-0.7mol/L之间，五价钒电解液在55℃时稳定时间超过7天，无沉淀产生。硫酸铁的加入对钒电解液的电化学活性影响不大。主要表现为：硫酸铁的加入并没有带来副反应；对电极反应的可逆性无明显影响；钒离子的电化学活性有微弱降低；电解液总电阻无明显变化；在单电池循环测试中，硫酸铁加入后，电池的容量和效率等性能并没有恶化，电池能够在50℃下稳定运行超过15天。硫酸铁能够稳定五价钒电解液是硫酸根铁离子共同作用的结果，这两种离子与五价钒离子的综合作用使得五价钒电解液的热稳定性极大提高。本文提出的含有高浓度硫酸铁的钒电解液制备工艺简单，电解液性能稳定，使用该电解液的电池在较高温度下运行良好，是一种具有工业化潜力的电解液。

As an effective and promising large-scale energy storage technology, all-vanadium flow battery technology has attracted wide attention due to its advantages of fast response, safety, reliability, independent design of capacity and power, and long cycle life. However, due to the instability of pentavalent vanadium in the positive electrolyte of all-vanadium flow battery at high temperature, it is necessary to add heat exchange system in the process of engineering amplification and stack design, which leads to the increase of cost of all-vanadium flow battery and limits the popularization and application of all-vanadium flow battery technology. In this paper, high-concentration ferric sulfate was used as an additive in the positive electrolyte of all-vanadium flow battery. The effects of different concentrations of ferric sulfate on the thermal stability, viscosity, electrochemical activity and battery cycle were studied by means of thermal stability test, cyclic voltammetry test, electrochemical impedance spectroscopy test, viscosity test and electrochemical cycling test. Raman spectroscopy and nuclear magnetic resonance vanadium spectroscopy were used to reveal the mechanism of stabilizing vanadium electrolyte by ferric sulfate. The results show that the thermal stability of pentavalent vanadium electrolyte can be greatly improved by adding ferric sulfate. When the concentration of pentavalent vanadium electrolyte is about 1.7 mol/L and the concentration of ferric sulfate is controlled between 0.5-0.7 mol/L, the stability time of pentavalent vanadium electrolyte is more than 7 days at 55 ℃ without precipitation. The addition of ferric sulfate has little effect on the electrochemical activity of vanadium electrolyte. The main manifestations are as follows: the addition of ferric sulfate does not bring side effects; it has no obvious influence on the reversibility of the electrode reaction; the electrochemical activity of vanadium ions decreases slightly; the total resistance of electrolyte does not change significantly. In the single cell cycle test, the capacity and efficiency of the battery did not deteriorate with the addition of ferric sulfate, and the battery could run steadily for more than 15 days at 50 ℃. Stabilization of pentavalent vanadium electrolyte is the result of the interaction of iron ions and sulfate ions. The combined action of these two ions and pentavalent vanadium ions greatly improves the thermal stability of pentavalent vanadium electrolyte. The preparation process of vanadium electrolyte containing high concentration of ferric sulfate is simple and the electrolyte is stable. Batteries using the electrolyte run well at relatively high temperatures. It is a potential electrolyte for industrialization.