双电层电容器水系防冻电解液中离子传输的电化学原位拉曼光谱研究

By virtue of environmental friendliness, facile fabrication and high power densities, electric double-layer capacitors (EDLC), in which aqueous solutions are often used as electrolytes，have drawn great attention. For the electrolytes, using neutral salts is advantageous over the commonly used acids or bases, such as wide potential window, green and more safety concern. More importantly, the appearance of anti-freezing additives makes the aqueous EDLC application at low temperature possible. Nevertheless, how to unveil the mechanism of ion flux into porous carbon when adding anti-freezing additives into electrolyte remains to be a challenge. In this project, referring our previous study, an electrochemical system will be built, in which NaClO4 aqueous solution, porous carbon and alcohols are selected work as electrolyte, electrode material and anti-freezing additives respectively. The in-situ Raman spectroelectrochemistry technology will be employed to this complex system. The solvation state of ions in different region (surface of electrode, bulk solution) will be analyzed according to the Raman shift of species during the electrochemical process. In addition, the influence of temperature and anti-freezing additives on ion solvation and ion transfer in different regions (surface of electrode, bulk solution) will be investigated systematically. Furthermore, molecule sieving effect of different pore sized carbon on various sizes of ion and anti-freezing additives will be also studied. To the end, this work will extend the application of Raman spectroelectrochemistry into the field of supercapacitors and provide novel idea for studying the surface and interface processes in complex electrochemical system. The results will also provide experimental evidence and theoretical foundation for fabrication of aqueous anti-freezing electrolytes, selection of activated carbon electrode materials and improvement of capacitor's performance.

水系双电层电容器具有绿色环保、功率密度高等特点。中性盐电解液具有比强酸强碱更宽的电化学窗口和更高的安全性，防冻添加剂的开发和应用提高了电容器的低温防冻能力。如何探索防冻添加剂在中性盐电解液中的作用机制仍是难点。结合前期工作，本项目选择活性炭为电极、高氯酸钠水溶液为电解液、醇类为防冻添加剂构建电化学体系，以离子从溶液体相迁移到活性炭电极表面的过程为研究对象，以电化学原位拉曼光谱为表征手段，根据此过程中不同区域内（溶液体相、电极表面）的拉曼光谱变化，分析对应区域内的离子溶剂化状态，考察温度、添加剂等因素对离子的络合状态和迁移过程的影响，从分子水平探讨不同孔径活性炭对传质离子及防冻添加剂的尺寸筛选效应。这一工作的开展将拓展光谱电化学技术在电容器领域的应用，为复杂电化学体系的表界面研究提供思路。所获研究成果也将为水系防冻电解液的开发、电极材料的选择和电容器器件性能的优化提供理论指导。

水系活性炭基双电层电容器具有绿色环保、功率密度高等特点。结合前期工作，本项目从活性炭电极材料制备、防冻电解液开发等角度出发，以电化学原位拉曼光谱等为表征手段，研究了活性炭电容器在不同电解液中离子从溶液体相迁移到活性炭电极表面的过程，根据此过程中不同区域内的拉曼光谱变化，分析了对应区域内的离子溶剂化状态。重点考察了活性炭孔结构、温度、添加剂等因素对离子的络合状态和迁移过程的影响，从分子水平探讨了不同孔径活性炭对传质离子及防冻添加剂的尺寸筛选效应。这些工作拓展了光谱电化学技术在电容器领域的应用，为复杂电化学体系的表界面研究提供了思路。所获研究成果也为超级电容器用活性炭制备、水系防冻电解液开发及电容器器件性能优化提供了理论指导。