全钒氧化还原液：电池电解液的研究

发布时间：2018-05-18 01:30

本文选题：钒电池 + 稳定性　；参考：《东北大学》2014年博士论文

【摘要】：全钒氧化还原液流电池(Vanadium redox flow battery,简称钒电池)是基于VO2+/VO2+与V2+/V3+电对的新型储能电池技术,能量存储于电解液中。钒电池与传统的蓄电池相比,具有可快速、大容量充放电,自放电率低,电池结构简单的特点。如何获得比能量高、性能稳定的电解液就是钒电池的关键问题之一。随着我国可再生能源法的正式实施,国家对风能、太阳能等新型能源发电非常重视。发展可再生能源需要大容量储能技术与之配套,结合我国具有丰富钒资源的优势,这就为建立大规模、低成本、可广泛使用的钒电池储能系统提供了广阔的发展空间。钒电池正负极电解液的基本组成为不同价态的钒离子+H2SO4+水,与其它二次电池不同,钒电池电解液不仅是导电介质,更是实现能量存储的电活性物质,是钒电池储能及能量转化的核心,因此钒电池的充放电效率、运行寿命和能量密度等关键性能都与电解液性能密切相关,特别是与电解液的的热力学性质有关。本课题主要研究的内容有：(1)在电解液中加入不同的添加剂,并进行电位滴定和紫外定量分析,考察钒电池电解液的稳定性,讨论添加剂对钒电池电解液还原性的影响。结果表明：钒电池正极电解液的温度越高,V(V)溶液越不稳定；温度相同的情况下,溶液中V(V)的浓度较高时,溶液稳定性变差；在电解液中加入少量的低浓度的添加剂时,可以明显的提高电解液的稳定性；H2SO4浓度恒定为2mol/L的情况下,V(V)浓度为1.5mol/L时,所选用的五种添加剂中草酸钠、草酸铵所起到的稳定效果较佳,当V(V)浓度为1.8mol/L,温度为40℃时,较适合选择尿素和CTAB,温度为50℃时,适合选择草酸盐；在紫外定量分析中,在不同浓度,不同温度下加入草酸钠和草酸铵后钒电池电解液中V4+含量均较高,草酸钠和草酸铵对于V5+的稳定性起到了抑制沉淀析出的作用。(2)利用电化学工作站测定循环伏安曲线、交流阻抗谱等研究添加剂对电解液的电化学反应可逆性及反应活性等性能的影响。结果表明：钒电解液中加入不同浓度添加剂时,电极反应活性有很大的提高,反应的可逆性也有上升,尤其草酸钠、草酸铵的阳极峰电流和阴极峰电流均较大；1.5mol/L VOSO4的硫酸溶液比1.8mol/L VOSO4的硫酸溶液有更好可逆性与电化学活性；加入添加剂后,电解液的电化学性能有所提升,交流阻抗谱中,加入草酸钠、草酸铵时电化学反应阻抗有所降低；加入3%CTAB.2%尿素时,电化学反应阻抗增大。(3)采用电导法测定极稀水-‘VOSO4二元溶液体系的解离常数,钒电池电解液中钒离子对的解离常数和钒离子的活度与电池性能直接相关,而且解离常数与温度有关,而与浓度无关,研究其随温度和组成的变化规律,进而研究钒电池的相关热力学性质,为进一步优化钒电池用电解液的工作提供部分理论基础。结果表明：硫酸氧钒极稀水溶液的电导率κ值随浓度的升高而增加,随温度的升高而降低；极限摩尔电导A。随温度的升高而增加；采用改进的Ostwald稀释定律和改进的Davies方程估算了硫酸氧钒离子对解离度a、活度系数γ和溶液的真实离子强度I；应用Fouss法和Shedlovsky法两种不同方法进行数据处理,解离常数、氧钒离子的迁移数、氧钒离子半径数据可以作为参考,解离度a随浓度和温度的升高而减小；计算不同温度下硫酸氧钒离子对解离过程的各热力学函数△G0、 △H0、△S0、△CP0值,并求得解离常数Kd与温度的关系经验方程式等等,可作为研究硫酸氧钒水溶液的热力学参考数据,为三元、四元溶液体系的研究提供理论依据。
[Abstract]:Vanadium redox flow battery (Vanadium redox flow battery) is a new energy storage battery technology based on VO2+/VO2+ and V2+/V3+ electric pairs. The energy is stored in the electrolyte. Compared with the traditional battery, vanadium battery has the characteristics of fast, large capacity charging and discharging, low self discharge rate and simple battery structure. How to obtain the specific energy High volume, stable performance electrolyte is one of the key problems of vanadium batteries. With the formal implementation of renewable energy law in China, the state attaches great importance to new energy generation, such as wind energy and solar energy. The development of renewable energy needs large capacity energy storage technology and matching, combined with the advantages of rich vanadium resources in China, this is to establish a big regulation The model, low cost and widely used vanadium battery energy storage system provides a broad development space. Vanadium battery positive and negative electrolyte is composed of vanadium ion +H2SO4+ water with different valence states. Unlike the other two batteries, the electrolyte of vanadium battery is not only conductive medium, but also an electroactive material for energy storage. It is the energy storage and energy of vanadium battery. The key properties of the quantity transformation are that the charge discharge efficiency, the operating life and the energy density of the vanadium battery are closely related to the performance of the electrolyte, especially the thermodynamic properties of the electrolyte. The main contents of this study are as follows: (1) adding different additives in the electrolyte and conducting potential titration and ultraviolet quantitative analysis. The stability of the electrolyte of vanadium battery was investigated and the effect of additives on the reducibility of the electrolyte was discussed. The results showed that the higher the temperature of the electrolyte of the vanadium battery was, the more unstable the V (V) solution was. Under the same temperature, the stability of the solution was worse when the concentration of V (V) was high, and a small amount of low concentration in the electrolyte was added to the electrolyte. When adding agent, the stability of the electrolyte can be obviously improved; when the concentration of H2SO4 is constant at 2mol/L, when the concentration of V (V) is 1.5mol/L, the stability effect of sodium oxalate and ammonium oxalate in the five additives is better. When V (V) concentration is 1.8mol/L and the temperature is 40, it is more suitable for the selection of urea and CTAB, when the temperature is 50 C. In the UV quantitative analysis, the content of V4+ in the electrolyte of vanadium battery after adding sodium oxalate and ammonium oxalate at different concentrations and temperatures is higher. Sodium oxalate and ammonium oxalate play a role in inhibiting precipitation in the stability of V5+. (2) use electrochemical station to determine the cyclic voltammetry curve, AC impedance spectroscopy and so on. The results show that the reaction activity of the electrode is greatly improved and the reversibility of the reaction increases, especially the Yang Jifeng current and the peak current of the cathode of ammonium oxalate; 1.5mol/L VOSO4. The sulfuric acid solution has a better reversible and electrochemical activity than the 1.8mol/L VOSO4 sulphuric acid solution; after adding the additive, the electrochemical performance of the electrolyte is improved. The electrochemical impedance of the electrochemical reaction is reduced when the sodium oxalate is added to the AC impedance spectrum, and the electrochemical impedance increases when the 3%CTAB.2% urea is added. (3) the conductivity method is used to measure the electrochemical impedance. The dissociation constant of VOSO4 two element solution system is constant. The dissociation constant of vanadium ion pair and the activity of vanadium ion in the electrolyte of vanadium battery are directly related to the performance of the battery, and the dissociation constant is related to the temperature, but it has nothing to do with the concentration, and studies the variation of the vanadium with the temperature and composition, and then studies the related thermodynamic properties of the vanadium battery. The theoretical basis for further optimization of the electrolyte for vanadium batteries is provided. The results show that the conductivity kappa value of the extremely dilute aqueous solution of vanadium sulfate increases with the increase of the concentration, and decreases with the increase of the temperature; the limit molar conductance A. increases with the increase of temperature; the improved Ostwald dilution law and the improved Davies equation are used. The dissociation degree a, the activity coefficient gamma and the true ionic strength I of the solution are calculated. The data processing, the dissociation constant, the migration number of vanadium ions, the oxygen vanadium ion radius data can be used as reference, the dissociation degree a decreases with the increase of concentration and temperature, and the difference temperature is calculated by two different methods of Fouss and Shedlovsky. The thermodynamic functions of the dissociation process, Delta G0, Delta H0, Delta S0, Delta CP0 value, and the relationship between the dissociation constant Kd and the temperature are obtained, and the thermodynamic reference data for the study of the solution of vanadium sulfate can be used as a theoretical basis for the study of three yuan and four element solution systems.
【学位授予单位】：东北大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM912

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