基于醌类衍生物电化学的全有机水系液流电池高电位电解质研究

All-vanadium redox flow battery shows the promising application prospects in many fields such as wind power and photovoltaic power generation as well as power grid peak shaving because of its high energy efficiency and long cycle life, the decoupling of energy and power, and low cost of construction. However, resource scarcity, high toxicity and potential hazards to the environment for vanadium element greatly restrict its practical application. In this application project, by exploiting excellent electrochemical reversibility of environmental friendly quinone compounds, the advantage that redox potentials can be conveniently tuned by modification of specific functional groups, and good compatibility with proton exchange membranes, with the guidance of quantum mechanical calculations based on density functional theory and molecular orbital theory, we attempted to design and synthesize high positive (negative) potential and high water-soluble quinone compounds. Synthetic laws for quinone compounds and “structure-activity” relationships between molecular structure, functional groups, charge density etc. and the potential, electrochemical kinetics parameters, and solubility were studied deeply in order to explore the electrochemical kinetics of electro-active quinone derivatives. And on this basis, all-organic aqueous redox flow batteries were assembled and evaluated. The electrode reaction kinetics was further improved by investigating the effects of active area of electrode, surface roughness, hydrophilicity etc. on electrochemical kinetic parameters and optimization of mass transfer parameters. The control mechanism of electrode involved catalysis and mass transfer and the charge-discharge behavior of organic electro-active species were revealed. This project can provide a new approach for the development of renewable redox flow battery based on organic small molecules.

全钒液流电池因其高的能量效率和循环寿命、功率与容量设计的解耦性以及低的组件成本，在风能和光伏发电以及电网调峰领域有着广阔的应用前景，然而钒元素的稀缺性、毒性及对环境的潜在危害极大地限制了它的实际应用。本申请项目拟利用环境友好的醌基化合物优异的电化学可逆性、可通过官能团修饰方便调控其氧化还原电位等性质的特点及其对质子交换膜良好的兼容性，借助基于密度泛函理论的量子力学计算和分子轨道理论的指导，设计合成高电位和水溶性的电活性醌基化合物，系统深入研究合成规律以及分子结构、官能团和电荷密度等与电极电位、电化学动力学参数和溶解度之间的“构效”关系，从而探索醌类衍生物电化学动力学的一般规律，并在此基础上构建全有机的水系液流电池单池，通过研究电极活性面积、表面粗糙度、亲水性等与电极动力学之间关系以及对电解液传质参数等优化以进一步改善电极反应动力学，揭示电极催化-传质的控制机制和有机电活性物质的充放电规律。

本课题旨在利用环境友好的有机分子优秀的电化学可逆性及电位和溶解度等性质可方便调控的特点，通过合成路线的理性设计，结合量子化学辅助模拟，获得了具有高正(或负)电位和良好水溶性的电活性有机化合物，包括卤代二羟基苯二磺酸衍生物、二羟基萘磺酸衍生物、羧基喹喔啉、聚吡咯蒽醌和聚吡咯喹喔啉等。系统研究了合成规律及分子结构单元与电位、动力学参数和溶解度之间的“构效”关系，探索有机分子电化学的一般规律。在此基础上，构建了多种水系液流电池单池体系，通过研究分子结构及其基本性质对开路电位、功率输出、倍率性能、效率和长程稳定性等的影响，揭示电极界面催化-传质的控制机制和长期循环中电活性分子的性能稳定或衰减的结构性因素。研究内容包括：(1)基于电活性分子的设计原则，合成和筛选得到多种具有优秀电化学性质和电池应用潜力的有机化合物，包括苯醌衍生物、蒽醌衍生物、喹喔啉衍生物、蒽醌基吡咯聚合物和喹喔啉基吡咯聚合物等; (2)系统研究了上述电活性有机材料的电位和物化性质及其影响规律，探索了其在水溶液体系中的电化学动力学规律，并提出了可能的电化学反应机理；(3)在此基础上，依据电活性有机材料电化学和物化性质的不同，合理组合构建了多种水系液流电池单池体系，研究了这些单池的性能、效率和循环稳定性，考察了材料的基本性质和电池结构参数等对性能和稳定性的影响规律。此外，考虑到电极界面的催化性质对电活性有机材料的电化学及其电池性能有重大影响及亲水性添加剂对提升水溶性方面的重要作用，我们还开展了2项与本课题密切相关的工作：(1) 催化性碳基电极材料的合成及其在水系有机液流电池上的应用；(2)水系碱性液流电池中用于增加活性电解质水溶性的添加剂的设计开发。比较遗憾的是，尽管我们通过反应路线设计得到了多个苯醌二磺酸的卤代产物和二羟基萘磺酸衍生物，但尚未找到合适的后处理纯化手段，产物纯度偏低，因而仅对其作了初步的结构表征和电化学性质研究。