水系锌基液流电池锌沉积诱导自愈合复合负极

The aqueous zinc-based redox flow battery has become one of the first choices for large-scale and high-efficiency energy storage technology because of its negative electrode potential, multi-electron reaction, fast kinetics, abundant reserves and low cost. The zinc negative electrode is an extremely core component of the system. However, the zinc negative electrode faces two key problems: the dendrite growth of zinc and the falling off of dead zinc particles. To this end, the applicant skillfully integrated the technical advantages of the additive and electrode structure optimization strategy, and proposed to functionalize a self-healing material with zinc the deposition-inducing additive, and then compound it with the carbon felt anode. Finally, the long cycle life composite carbon felt with the function of both zinc deposition-inducing and self-repairing would be obtained. In addition, the composite negative electrode also has the ability to grow zinc in a limited area and re-use the deciduous zinc. By controlling the preparation processes of functionalized self-healing material and composite, the composite anode with the best composition and structure was obtained, and the mechanism of zinc deposition induction and self-healing were studied, and the structure-activity relationship among composition, structure, zinc morphology and battery performance was established. This work would provide theoretical basis and technical support for the development of high-performance composite anodes for aqueous zinc-based flow batteries.

水系锌基液流电池因锌负极本身具有电极电势较负、多电子反应、动力学快、储量丰富及成本低等特点，使其成为大规模高效储能技术的首选之一。锌负极是该系统中极其核心的部件。但锌负极面临两大关键问题：锌的枝晶生长与死锌颗粒脱落。为此，申请者巧妙地整合添加剂与电极结构优化策略的技术优势，提出将自愈合材料用锌沉积诱导添加剂进行功能化改性，并将其与碳毡负极可控复合，制备出集锌沉积诱导功能与自修复功能为一体的长循环寿命复合碳毡负极。此外，该复合负极还具有锌限域生长、容纳并重新利用脱落的锌的能力。通过调控功能化自愈合材料与复合碳毡负极的制备工艺，获得最优组成及结构的复合负极，研究锌沉积诱导机理与自愈合机理，并建立“组成-结构-锌形貌-电池性能”构效关系，为水系锌基液流电池用高性能复合负极的研发提供理论依据和技术支持。

水系锌基液流电池具有安全性高、成本低、能量密度相对较高等优势，在分布式储能领域拥有广阔的应用前景。该电池体系中负极锌在水系电解液中的沉积/溶解反应，具有适宜的电极电势（-0.76 V，相对于标准氢电极）、两电子转移、动力学快等特点。然而，在充放电过程中，负极锌的不均匀沉积/溶解，极易造成枝晶生长与死锌脱落，从而对电池的循环寿命与库伦效率产生恶劣的影响。此外，随着锌沉积面容量的增加，该影响就越发严重。深入理解锌的电化学沉积行为，调控锌均匀沉积，研发高性能锌负极，对水系锌基液流电池的发展至关重要。在本项目支持下，围绕水系电解液中锌负极的关键科学问题，开展了锌沉积机理研究与锌沉积行为调控工作。针对锌基液流电池锌沉积过程中锌离子浓度不断降低的特性，剖析了锌离子浓度对锌沉积形貌作用机理，建立了“锌形貌-库伦效率”的构效关系，从而提出了可维持液流电池高效运行的电解液极限利用率的计算方法；研究了乙二醇共溶剂对锌沉积形貌的影响，并证明该共溶剂可有效整平锌沉积形貌，提升锌负极的循环稳定性；利用N-甲基-N-乙基溴化吡咯烷电解液添加剂调控锌沉积形貌，提升了锌负极的循环寿命，揭示了其阴、阳离子在电解液中所发挥的作用；利用电极的宏观“尖端效应”优化电极结构，构建了新型非平面耦合电极，对锌负极表面电场及流场进行优化，调控锌枝晶的生长位置，有效缓解了枝晶刺破隔膜所带来的不利影响，提升了锌沉积面容量及其在高面容量条件下的循环稳定性，使得锌碘液流电池可在40 mA/cm2的电流密度下实现240 mAh/cm2的超高面容量，并能以160 mAh/cm2的高面容量稳定循环300次以上。本项目深入研究了锌沉积的作用机理与影响因素，建立了锌形貌与电池性能的构效关系，加深了锌在水系电解中电化学沉积行为的理解；提出了一种极具创新性的负极结构，大幅度提升了电池的性能。本项目所取得的研究成果，为进一步提升锌负极的性能提供有价值的参考，有助于推动锌基液流电池更好的发展。项目执行期间，发表SCI论文4篇，申报发明专利3件。

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