全钒液流电池电解液中活性离子淌度的测定与表征

发布时间：2018-03-24 11:42

本文选题：全钒液流电池　切入点：离子淌度　出处：《江苏大学》2017年硕士论文

【摘要】：近年来,风能、太阳能等可再生能源在能源危机以及环境污染的背景下得到快速发展。然而,这些可再生能源本质上是间歇性的,只有发展出有效的、安全的、廉价的、可靠的储能系统才能使可再生能源实用化。储能技术在改善电网稳健性、削峰平谷以及调节负载方面起着关键的作用。液流电池因具有不依赖于地理条件,可将功率密度与能量密度分开,适用于多种场合的应用等特点,被认为是最有前景的储能技术。其中全钒液流电池(VRFB)技术最为成熟,全钒液流电池由电极、交换膜和钒电解液组成,具有能量效率高,寿命长,无离子交叉污染且价格低廉等优点。其可作为大型储能装置,将不稳定的可再生能源转化为化学能储存起来,在使用时,电解液的化学能将转化成电能输出。然而,全钒液流电池在商业化应用的过程中还面临着一些技术问题,包括离子交换膜并不具有完美的选择性以及较低的功率密度和能量密度。提高功率密度可以降低电池成本、提高能量效率且使电池变得对负载变化更有变通性。功率密度是由动力学极化,欧姆极化和传质极化决定的。欧姆极化和传质极化直接与耦合的传质与电荷传输有关。所以,发展有足够大活性面积的多孔介质电极以及加深对全钒液流电池中的传输过程和特性的理解具有重要的意义。然而,全钒液流电池是一个复杂的多尺度系统,并且包含了在多孔电极中的多相流和电化学反应。因此很少有关于全钒液流电池多孔电极内传输特性以及对应的对功率密度影响的研究。本文的立意与基本思路主要是针对全钒液流电池多孔电极内传质特性表征的方法进行创新性的改进(主要体现在离子淌度的测定与表征上)。目前全钒液流电池使用的离子淌度表达式没有包含离子间以及离子和溶剂之间的相互作用力。针对全钒液流电池电解液中活性离子淌度表达式的缺陷,本文基于全钒液流电池电极传质的理论框架,结合电化学原理与多孔介质传输理论,提出了用不同电场强度下电池的极限电流之间的差异,来间接获得真实的离子淌度的理论模型。本文结合外加平行电场与新设计的电池结构,设计并组装了一套灵活创新的实验装置,系统地研究了电解液浓度和电解液流量对离子淌度这一传输参数的影响。实验通过调节平行板间距分别为3.5 cm、7 cm以及控制外加电压的大小分别为0 V、0.5 V、4 V、32 V来改变电场强度的大小和方向。实验控制发生传质极化侧半电池钒离子浓度分别为0.1 M、0.2 M和0.4 M,或者控制电解液流量分别为6 m L/min、12 m L/min和18 m L/min。本文阐述了实验过程中遇到的并有效解决的四个实验难点,即:电解液具有强腐蚀性、V2+离子极易被氧化而不能保证电池的SOC一致、集流板对外加电场产生的静电屏蔽作用以及铝箔板结构缺陷对场强分布产生影响这四个棘手问题。提出的解决方法对类似的实验体系有积极的指导意义。实验结果表明,外加电场对全钒液流电池的极限电流密度影响较小,本文提出三种可能的原因来解释这个现象。最后,在实验数据的基础上,对一类特定工况范围内的离子淌度拟合了其与电解液浓度的关联式,该公式体现了离子浓度和离子大小的影响。
[Abstract]:In recent years, wind energy, solar energy and other renewable energy in the rapid development of the energy crisis and environmental pollution under the background. However, these renewable energy is intermittent, only the development of an effective, safe, cheap, reliable storage system to make renewable energy utility energy storage technologies to improve the power grid. Conservatism plays a key role in regulating the load peak and Pinggu. Because of the flow battery is not dependent on the geographical conditions, can separate the power density and energy density, application of the model is suitable for various occasions, is considered the most promising energy storage technology. The vanadium redox flow battery (VRFB) the most mature technology, the vanadium redox flow battery is composed of electrode, membrane and vanadium electrolyte composition, with high energy efficiency, long life, the advantages of no ion cross contamination and low price. It can be used as a large storage device will be unstable The renewable energy into chemical energy stored, when in use, the electrolyte chemical energy into electrical energy output. However, in the process of commercial application is still confronted with some technical problems of VRB, including ion exchange membrane does not have the choice of perfect and low power density and energy density. Increasing power density can reduce battery costs, improve energy efficiency and make the battery become to load change more flexibility. The power density is determined by dynamic polarization, ohmic polarization and mass transfer polarization is determined. The ohmic polarization and mass transfer of direct coupling with mass transfer and charge transfer. Therefore, the development of a porous electrode enough the large active area and enhance the transmission process and characteristics of the battery in the vanadium redox flow understanding is of great significance. However, the vanadium redox flow battery is a complex multi scale system In the system, and includes the multiphase flow in porous electrode and the electrochemical reaction. So the research has little effect on the vanadium redox flow battery transmission characteristics in porous electrodes and the corresponding to the power density. And the basic ideas of this thesis is mainly improved method for VRB porous electrode in mass transfer characterization the innovative (mainly embodied in the determination and characterization of ion mobility on ion mobility). Current use of all vanadium redox flow battery contains no degree expression of interaction between ions and ions and solvent. Aiming at the defects of all vanadium flow of electrically active pool electrolyte ion mobility expressions, the theoretical framework of this article all vanadium redox flow battery electrode mass transfer based on the combination of electrochemical principle and porous media transmission theory, put forward the difference between the current limit under different electric field strength of the battery, to indirectly obtain true The theoretical model of ion mobility. This paper applied the parallel electric field and the new design of the cell structure, designed and constructed a set of experimental device of flexible and innovative, systematic study of the influence of the concentration of electrolyte and electrolyte flow on the ion mobility the transmission parameters. Experiments by adjusting the parallel plate spacing was 3.5 cm. 7 cm and control the size of the applied voltage were 0 V, 0.5 V, 4 V, 32 V to change the size and direction of the electric field intensity. The mass transfer side half cell vanadium ion concentration polarization control experiment were 0.1 M, 0.2 M and 0.4 M, or control of electrolyte flow was 6 m L/min. 12 m L/min and 18 m L/min. this paper describes four experiments and solve the difficulties encountered in the process that has strong corrosive electrolyte, V2+ ions can be easily oxidized and can not guarantee that the battery SOC, collector plate external electric field generated static Electric shielding and aluminum foil structural defects influence the four thorny problems on electric field distribution. The proposed solution has a positive guiding significance for similar experimental system. The experimental results show that the influence of limiting current density smaller electric field on all vanadium redox flow battery, this paper proposes three possible reasons to explain this. The phenomenon. Finally, based on the experimental data, ion mobility for a class of specific conditions within the scope of the degree of fitting with the electrolyte concentration correlation, the formula reflects the influence of concentration and size of ions.

【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912

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