液流锂离子电池电极反应的界面微观机理及动力学研究

Redox flow lithium-ion battery, which is based on redox targeting reactions and combines the advantages of great system flexibility of redox flow batteries with the high energy density of lithium-ion batteries, is poised to provide a new approach for large-scale high density electrochemical energy storage. To improve the energy density and rate capability of redox flow lithium-ion battery, this project constructs a new cathodic electrode system based on LiNi8Co1Mn1O2 and plans to have a deep insight about the dynamic characteristics of the electrochemical and chemical process in redox targeting reaction and the coordination mechanism between the two different processes. The effects of mediator molecular concentrations and particle sizes of electrode material on the interface adsorption and percolation threshold would be deeply investigated by an in situ experimental technique combined with electrochemical quartz crystal microbalance and in situ Raman spectroscopy. Meanwhile, the mechanisms of charge carrier lateral propagation in self-assembled mediator molecular monolayer and lithium ions cross-interface transfer will be concluded finally. All these studies could realize the optimum design of redox flow lithium-ion battery and give a theoretical support to development of the next generation of high energy density redox flow batteries.

为了提高基于氧化还原靶向反应的液流锂离子电池的能量密度和倍率性能，推动其实用化和产业化进程，本项目构建了基于镍钴锰三元材料（LiNi8Co1Mn1O2）为正极活性物质的氧化还原靶向反应新体系，同时以电极材料与媒介分子的氧化还原靶向反应为研究对象，通过调控媒介分子的浓度和电极材料的尺度，考察电化学和化学反应的动力学，最终通过电化学和化学过程的优化耦合获得倍率性能优异的液流锂离子电池；利用电化学石英晶体微天平、扫描电化学显微镜和电化学现场拉曼光谱组成的原位实验技术来研究调控因素对界面吸附和逾渗现象的调控规律，探讨载流子在媒介分子自组装层内的二维传递的微观机理和媒介分子/电极材料界面的物质迁移过程，为氧化还原靶向反应在电池技术领域的推广和新型高能量密度液流电池体系的研发提供理论依据和基础数据支持。

液流电池是一种将活性物质溶于电解液，将电池的容量单元和功率单元分开的电池体系，但是受限于活性物质的溶解度，液流电池的能量密度普遍偏低。因此，为了提高液流电池体系的能量密度，利用氧化还原靶向反应，即利用电位合适的氧化还原媒介分子，与分散在电解液中的固体活性物质进行可逆的氧化还原反应，实现固体活性物质的可逆充放电，在实现容量单元和功率单元分开的同时，完成固体活性物质的储能。课题的研究内容分为三部分：（1）以水作为靶向媒介K3Fe(CN)6/K4Fe(CN)6的溶剂，并以磷酸铁锂作为电极材料，探索磷酸铁锂（LiFePO4）材料在含有靶向媒介的水相电解液中的电化学行为及其与靶向媒介的相互作用；（2）用全钒液流电池的电极反应为反应媒介，通过能斯特电位驱动，将能量储存在固体活性物质铁氰化钒中，研究了铁氰化钒与VO2+/VO2+电偶对的相互作用；（3）利用镍铁双金属氢氧化物作为载体，制备复合硫正极材料，有效的提升了锂硫电池的循环寿命，经1000次循环后其容量保持率为72%。