Collaborative Research: Designing Solid Boosters and Electrolytes for Redox-Targeting Flow Batteries

氧化还原液流电池（rfb）被认为是最有前途的储能技术之一，可以实现向碳中性电网的过渡。rfb为电网应用程序提供了许多好处，包括分离能量和功率额定值的能力、相关的、前所未有的可扩展性以及长期存储的成本效益。然而，氧化还原活性物质在电解质中的低溶解度一直是目前面临的挑战。解决这一限制的一个有希望的方法是利用储罐中的固体电荷存储（增压）材料，通过间接氧化还原靶向反应可逆地还原或氧化电解质中的溶解物质。这样，容量不再取决于可溶物质的浓度，而是取决于罐中固体物质的数量。这一概念展示了利用固相和液相氧化还原化学的独特优势的前景，将前者的高能量密度与后者的可扩展性和安全性相结合。该研究的成功实施将有助于解决RFBs广泛采用的主要障碍。这将使更多地利用可再生资源并减少与能源有关的排放。它将通过有效管理与能源需求和供应脱钩的不必要波动，提供电网的弹性和灵活性。该研究项目包括有益社会影响的教学方面。其综合的、跨学科的性质将有助于培养多样化的能源科学和工程劳动力，使其在材料研究的多个方面具有素养。课程的改进和推广将有利于一系列本科生和研究生的教育，并指导中学和社区大学的学生，特别是那些代表性不足的少数群体的学生，在可持续能源的战略领域从事STEM职业。本研究项目将通过研究间接氧化还原靶向反应的基本原理，即热力学、反应动力学、质量和电荷输运，深入了解间接氧化还原靶向反应的本质。支持该方法的两个具体原则是：(1)金属六氰化金属酸盐（mhcm）对还原电位（E°）具有粗、细两种调节能力，可以调节还原电位（E°）以减小介质和助推器之间的还原电位差距；(2)由于氧化还原靶向液流电池的能量密度是由助推器材料的数量而不是电解液中活性物质的浓度决定的，因此在组成对称的电解液中，阳极液和阴极液的浓度都可以适中。将探讨插层阳离子对E°的影响，从这些研究中获得的热力学和动力学信息将在计算模型中实现，以提供第一性原理知识。由此产生的知识也将为利用间接氧化还原靶向反应的其他电化学相关领域提供见解，例如水电解和燃料电池。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Redox flow batteries (RFBs) are considered one of the most promising energy storage technologies to enable the transition toward a carbon-neutral electricity grid. RFBs offer many benefits for grid applications, including ability to decouple energy and power ratings, the associated, unprecedented scalability, and the cost-effectiveness in long-duration storage. However, low solubility of the redox active species in the electrolyte have so far presented challenges. One promising approach to address this limitation is the utilization of solid charge storage (booster) materials in the tanks to reversibly reduce or oxidize dissolved species in the electrolyte via indirect redox-targeting reactions. In this way, the capacity is no longer dependent on the concentration of soluble species but rather the quantity of solids in the tanks. This concept demonstrates the promise for exploiting the unique benefits of solid- and liquid-phase redox chemistry, combining the high-energy-density of the former with the scalability and safety of the latter. Successful implementation of the research will contribute to addressing the key obstacles to widespread adoption of RFBs. This will enable greater utilization of renewable sources and reduce energy related emissions. It will provide grid resilience and flexibility by effectively managing unwanted fluctuations with decoupled energy demand and supply. The research project includes pedagogical aspects of beneficial societal impact. Its integrated, interdisciplinary nature will aid in training a diverse energy science and engineering workforce to be literate in multiple aspects of materials research. Curriculum enhancements and outreach will benefit the education of a range of undergraduate and graduate students and mentor secondary and community college students, especially those of underrepresented minority groups, toward STEM careers in the strategic area of sustainable energy.This research project will provide an in-depth understanding of the nature of indirect redox targeting reactions by investigating the fundamental principles, i.e., thermodynamics, reaction kinetics, and mass and charge transport. Two specific principles underpinning the approach are: (1) Metal hexacyanometallates (MHCMs) possess both coarse and fine adjustments to reduction potential (E°), which can be tuned to minimize the gap in reduction potential between mediators and boosters, (2) because the energy density of redox targeting flow batteries is set by the quantity of booster material, rather than the concentration of active materials in the electrolyte, moderate concentration of both anolyte and catholyte can be used in a compositionally symmetric electrolyte. The effects of intercalation cations on E° will be probed, and thermodynamic and kinetic information from these studies will be implemented in a computational model to provide first-principles knowledge. The resulting knowledge will also provide insights into other electrochemistry-related fields utilizing the indirect redox targeting reactions, such as water electrolysis and fuel cells.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.