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

氧化还原液流电池(RFB)被认为是最有前景的储能技术之一，可以实现向碳中性电网的过渡。RIB为电网应用提供了许多好处，包括将能源和额定功率分离的能力、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，氧化还原活性物种在电解液中的低溶解性到目前为止一直是一个挑战。解决这一局限性的一个有希望的方法是利用储罐中的固体电荷存储(助推器)材料，通过间接氧化还原靶向反应可逆地减少或氧化电解液中的溶解物种。这样，容量不再取决于可溶物质的浓度，而是取决于储罐中固体的数量。这一概念展示了利用固态和液态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。这项研究的成功实施将有助于消除广泛采用RFB的主要障碍。这将使可再生能源得到更大的利用，并减少与能源相关的排放。它将通过分离能源需求和供应来有效管理不必要的波动，从而提供电网的弹性和灵活性。该研究项目包括有益的社会影响的教学方面。它的综合性、跨学科性质将有助于培养一支多样化的能源科学和工程劳动力，使其精通材料研究的多个方面。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，并指导中学生和社区大学生，特别是那些在可持续能源战略领域从事STEM职业的少数族裔学生。本研究项目将通过研究热力学、反应动力学、质量和电荷传输等基本原理，深入了解间接氧化还原靶向反应的性质。支持该方法的两个具体原则是：(1)金属六氰酸盐(MHCM)对还原电位(E°)具有粗略和精细的调节，可以调节以最小化介体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，因此在成分对称的电解液中可以使用中等浓度的阳极液和阴极液。将探讨插层阳离子对E°的影响，这些研究的热力学和动力学信息将在计算模型中实施，以提供第一性原理知识。所获得的知识还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，如水电解和燃料电池。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.