Elucidating Degradation Mechanisms of High-Potential Redox Electrolytes in Nonaqueous Redox Flow Batteries

可再生能源，如太阳能和风能，是减少与化石燃料有关的能源和环境风险的有希望的替代品。然而，这些自然产生的可再生能源是间歇性的，这意味着能源不能持续生产或满足需求水平。因此，有必要储存能量，以便在需要时释放。氧化还原液流电池（RFB）使用基于溶液的材料用于能量存储，并且由于其低成本和可靠性而引起了显著的关注，但是其低能量密度和不稳定性阻碍了其广泛应用。本提案的目的是开发用于RFB的新型无金属化合物，以提高其能量密度。具体而言，研究人员的目标是开发一种新的化合物家族，即联吡啶和四硫富瓦烯（TTF），具有（1）在有机溶剂中的高溶解度，（2）高电池电压下的延长氧化还原电位，以及（3）长循环寿命的高电化学可逆性。利用研究成果作为外联活动的基础，研究人员将吸引不同的学生和公众，以提高他们对可再生能源科学的理解，更广泛地说，化学可持续性。此外，拟议的外展活动将帮助公众了解实验室的基础研究与日常生活中的可再生能源之间的联系，同时提高他们的科学素养，并为本科生和研究生提供发展科学沟通技能的机会。（1）设计、合成和表征分子、高氧化还原电位、无金属的联吡啶和TTF衍生物的物理和氧化还原性质，（2）研究了它们在非水氧化还原液流电池（NRFBs）中的应用，并通过原位循环伏安法以及紫外-可见光谱和傅立叶-可见光谱研究了它们的潜在分解机理。变换红外光谱研究人员假设，衍生物的电子和空间性质，以及它们的热力学和电动力学，可以使用分子工程进行微调，从而提高它们在NRFBs中的稳定性和循环效率。这项研究将推进知识的设计原则，指导高氧化还原电位，大电化学可逆性，增强传质系数和高电子转移速率的氧化还原活性化合物的合成的前沿。该提案中所做的工作将填补有前途的NRFBs的开发与缺乏理想的氧化还原电解质之间的知识空白，并产生对理想氧化还原活性化合物的关键基本见解。该奖项反映了NSF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。

Renewable energy sources, such as solar and wind energy, are promising alternatives to reduce the energy and environmental risks associated with fossil fuels. However, these naturally occurring renewable energy sources are intermittent, meaning that the energy cannot be produced constantly or respond to meet demand levels. Therefore, it is necessary to store energy for release when needed. Redox flow batteries (RFBs) use solution-based materials for energy storage and have attracted remarkable attention due to their low cost and reliability, yet their widespread application is hindered by their low energy density and instability. The objective of this proposal is to develop novel metal-free compounds for RFBs to enhance their energy density. Specifically, the investigators aim to develop a new family of compounds, namely bipyridine and tetrathiafulvalene (TTF), with the necessary combination of (1) high solubility in organic solvents, (2) extended redox potentials for high battery voltage, and (3) high electrochemical reversibility for long cycling lifetime. Using the research outcomes as the basis for outreach activities, the investigators will engage a diverse body of students and the general public to enhance their understanding of renewable energy science and, more broadly, chemistry for sustainability. Furthermore, the proposed outreach activities will help the public understand the connection between fundamental research in laboratories and renewable energy in daily lives while increasing their scientific literacy and will provide opportunities for undergraduate and graduate students to develop their science communication skills.This proposed project aims to achieve two goals: (1) design, synthesize, and characterize the physical and redox properties of molecular, high-redox-potential, metal-free bipyridine and TTF derivatives, and (2) investigate their application in nonaqueous redox flow batteries (NRFBs) and elucidate their potential decomposition mechanisms using in situ cyclic voltammetry as well as operando UV-Vis and Fourier-transform infrared spectroscopies. The investigator hypothesizes that the electronic and steric properties of the derivates, as well as their thermodynamics and electrokinetics, can be finetuned using molecular engineering, thus improving their stability and cycling efficiency in NRFBs. This research will advance the frontiers of knowledge in design principles that guide the synthesis of redox-active compounds with high redox potentials, great electrochemical reversibility, enhanced mass transfer coefficients, and high electron transfer rates. The work done in this proposal will fill the knowledge gap between the development of promising NRFBs and the lack of ideal redox electrolytes, as well as generate key fundamental insights into ideal redox-active compounds. The conclusions drawn from this research will have a profound impact on battery performance enhancement design.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.