水系有机液流电池及隔膜

The exploration of energy saving materials and processes is the key to the practical application of energy from renewable sources. Since the first demonstration of aqueous organic redox flow battery in 2014, which exploits water as solvent and organic molecules as redox active electrolytes, it has been anticipated to be the most promising technique for massively storing renewable energy. However, its performance must be further improved to meet the demand of practical application. The key to further improvement of aqueous organic redox flow battery performance lies in understanding how molecular structure of the electrolytes and the membranes inside determines the most critical parameters of aqueous organic redox flow battery, which include energy density, power density, efficiency and cycle life. In this proposal, we will focus on the molecular design of electrolyte and membrane materials. By systematically controlling and tuning the structural characteristics of electrolytes, for instance substituents, steric hindrance, charge density, etc., we would design, synthesize novel electrolytes for aqueous organic redox flow battery and characterize their electrochemical properties and stability. By exploiting the fast transportation of inorganic ions in confined nano-space, we will fabricate ionic membranes with intrinsic microporosity and by regulating the structure of the intrinsic channels, we would establish a method to tune membrane permeability and selectivity. By carefully screening the electrolyte structure and membrane morphology, a lab-scale aqueous organic redox flow battery will be assembled and thoroughly characterized. Based on experimental results, we would establish the relationship between electrolyte structure, membrane morphology and flow battery performance and propose strategies to improve battery performance via molecular design. The results of this project will provide fundamental knowledge for the design, improvement and development of aqueous organic redox flow battery and benefit its practical application.

储能材料、过程的研究是可再生能源高效率、大规模利用的关键，以水为溶剂、有机分子为储能介质的有机液流电池过程，自2014年报道以来，被认为是最具应用潜力的新型储能过程，然其发展时间短、性能尚不能满足规模化应用要求，解决这一问题的关键在于阐明电解质、隔膜材料分子结构对电池宏观性能（能量密度、功率密度、效率、循环寿命等）的调变规律。本项目从有机电解质、隔膜分子设计出发，通过调控电解质分子的结构特征（取代基、位阻、电荷等），设计新型电解质分子，系统表征其氧化还原反应行为、稳定性；利用限域空间内离子的传质传递特征，制备限域通道离子膜并通过通道设计，调控液流电池隔膜的选择性和渗透性。优选电解质分子、隔膜材料，组装液流电池，表征电池宏观性能，阐明分子结构对电池性能的调变规律。本项目的研究成果将为水系有机液流电池设计提供理论依据，为其规模化应用提供指导。

水系有机液流电池以水溶性有机物为储能介质，具备成为新一代储能技术的多个重要特征，是储能技术的前沿研究领域。然而，水溶性有机电活性分子的稳定性仍待提高、分子结构和电化学性质、电池性能之间的构效关系不清，缺乏面向水系有机液流电池的专用离子传导膜，这些问题严重制约了水系有机液流电池在储能领域的规模应用和推广。本项目从微观结构入手，通过水系有机液流电池电解质的分子结构设计、隔膜材料的高分子结构设计，调控水系有机液流电池能量密度、功率密度、效率以及循环寿命等重要宏观性能。主要研究内容包括：（1） 水系有机液流电池电解质分子的结构设计、合成和表征；（2）基于“限域”传质理论，设计高选择性、低阻抗的液流电池隔膜材料，建立隔膜的分子结构、通道对电池性能的调变规律、设计准则；（3）立足于电解质分子结构对电池性能的调控规律以及隔膜材料的设计准则，开发满足商业预期的水系有机液流电池。主要研究结果包括：（1）开发了多电子储能电解质分子；提出了仿生电活性分子设计策略、多电子储能分子设计方法和电解质分子稳定性的“溶剂化调控”策略，大幅提升有机液流电池的综合性能；（2）提出将离子的跨膜传递限制在自具微孔离聚物膜的亚纳米孔道内，利用微孔的孔筛分效应，提高选择性；利用受限空间内增强的相互作用，加速离子传递，提高传导性，大幅提升了水系有机液流电池循环稳定性和能量效率，实现了有机液流电池快充；（3）实现了面向有机液流电池体系的自具微孔离聚物膜规模制备及示范应用。通过项目实施，在Angew Chem Int Ed、Energy Environ Sci、Chem、JACS Au, Adv Funct Mater等期刊发表论文27篇，申请发明专利3件，研究成果获得2022年中国化工学会基础研究成果二等奖。