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

太阳能和风能等可再生能源是降低与化石燃料相关的能源和环境风险的有前途的替代能源。然而，这些自然产生的可再生能源是间歇性的，这意味着能源不能不断生产，也不能满足需求水平。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)采用溶液为基础的储能材料，因其成本低、可靠性高而备受关注，但其低能量密度和不稳定性阻碍了其广泛应用。这项提议的目的是为RFB开发新型的无金属化合物，以提高其能量密度。具体地说，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性，(2)高电池电压的扩展氧化还原电位，以及(3)长循环寿命的高电化学可逆性的必要组合。利用研究成果作为外展活动的基础，调查人员将让不同的学生和公众参与进来，以增进他们对可再生能源科学以及更广泛地说，化学促进可持续发展的了解。此外，拟议的外展活动将帮助公众了解实验室基础研究与日常生活中可再生能源之间的联系，并将为本科生和研究生提供发展科学交流技能的机会。这项拟议的项目旨在实现两个目标：(1)设计、合成和表征分子、高氧化还原势、无金属的联吡啶和TTF的物理和氧化还原性质；(2)研究它们在非水氧化还原液流电池(NRFB)中的应用，并使用原位循环伏安法以及操纵性紫外可见光谱和傅立叶变换红外光谱来阐明其潜在的分解机理。研究人员假设，这些衍生物的电子和空间性质，以及它们的热力学和电动力学，可以通过分子工程进行微调，从而提高它们在NRFB中的稳定性和循环效率。这项研究将推进设计原则的知识前沿，指导合成具有高氧化还原电位、极大的电化学可逆性、增强的传质系数和高电子传递率的氧化还原活性化合物。这项建议中所做的工作将填补有前途的NRFB的开发和理想氧化还原电解液缺乏之间的知识差距，并对理想的氧化还原活性化合物产生关键的基本见解。这项研究得出的结论将对电池性能增强设计产生深远影响。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。

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.