离子传导膜对碱性锌铁液流电池锌沉积形貌调控机制的研究

Alkaline zinc-iron flow battery is a high efficiency energy storage technology. However, the reliability and stability of this battery is hindered by zinc dendrites/accumulations, which has been regarded as one of the most critical issues for the practical application of the alkaline zinc-iron flow battery. Recently we firstly utilize an ion conducting membrane to adjust the zinc morphology and tackle zinc dendrite/accumulation for the alkaline zinc-iron flow battery, which provides a totally new way for zinc morphology control. This project will focus on the key problem of ion conducting membranes for alkaline zinc-iron flow battery to address the issue of zinc dendrite/accumulation. High performance composite porous ion conducting membranes will be designed and fabricated by associating the membranes with the factors affecting the zinc dendrite/accumulation (including the distribution of current density, temperature and zincate concentration). By employing theoretical-experimental method, (1) the regulation mechanism of the designed membranes with different structures on the electrochemical behavior of zinc anode will be clarified deeply, (2) the influence rules of distribution of current density, temperature and zincate concentration on zinc morphology will be uncovered and (3) the strategies for adjusting zinc morphology will be established. A uniform and compact zinc platting procedure thus will be finally realized, which will supply technical support for dramatically enhancing the performance including cycling stability of the alkaline zinc-iron flow battery and meanwhile, accelerating step for this kind of battery moving forward.

碱性锌铁液流储能电池是一种高效储能技术，锌枝晶及锌累积问题严重影响着该电池的循环稳定性，制约了该电池的实用化。近期，申请者提出了用离子传导膜来调控锌沉积形貌、解决锌枝晶及锌累积问题的设想，为碱性锌铁液流储能电池锌沉积形貌的调控开创了一条全新的思路。本项目针对锌枝晶及锌累积对碱性锌铁液流储能电池带来的循环稳定性差的问题，将离子传导膜与影响锌沉积形貌的关键因素包括电流密度分布、温度分布及电解液中活性物质浓度分布等相关联，设计制备高性能复合多孔离子传导膜。通过实验与理论计算相结合的方法，深入研究复合多孔离子传导膜对碱性锌铁液流储能电池锌负极电化学行为的调控机制，揭示电流密度分布、温度分布及电解液中活性物质浓度分布对锌沉积形貌的影响规律，建立复合多孔离子传导膜对锌沉积形貌的调控策略，从而获得均匀致密的锌沉积层，提高碱性锌铁液流储能电池循环稳定性，为碱性锌铁液流储能电池的发展提供技术支撑。

碱性锌铁液流电池具有电解液成本低、电池电压高、安全性好等特点，近年来得到了广泛关注。碱性锌铁液流电池中存在的关键挑战在于：负极锌在碱性条件下不均匀沉积造成锌枝晶和锌累积的问题导致电池循环稳定性较差。此外，碱性锌铁液流电池在充电过程中，负极金属锌的沉积会沿着膜和电极两侧方向生长，沿着膜方向不断生长的锌易形成枝晶并对膜造成破坏使电池短路失效。针对这一关键技术问题，本工作从影响锌沉积过程的关键因素出发，将复合多孔离子传导膜引入到碱性锌铁液流电池中，通过对复合多孔离子传导膜的结构进行设计来调控膜与电极界面处性质，包括膜与电极界面处的温度分布（传热过程）、活性物质浓度分布（传质过程）、电流密度分布，阐明了复合多孔离子传导膜对碱性锌铁液流电池负极锌沉积形貌的调控机制，建立了复合多孔离子传导膜对锌沉积形貌的调控策略，获得了均匀致密的锌沉积形貌，将碱性锌铁液流电池面容量提高至240 mAh cm-2、运行工作电流密度提高至260 mA cm-2，在260 mA cm-2的高工作电流密度下，电池连续稳定运行近800个循环性能保持稳定，电池平均能量效率保持在80％以上。研究结果为锌沉积形貌的调控及电池性能的提高提供了重要指导意义。