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，是减少与化石燃料相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进行能量存储，由于其低成本和可靠性而受到广泛关注，但其低能量密度和不稳定性阻碍了其广泛应用。本研究的目的是为rfb开发新型的无金属化合物，以提高其能量密度。具体来说，研究人员的目标是开发一个新的化合物家族，即联吡啶和四硫代富勒烯（TTF），它们具有(1)在有机溶剂中的高溶解度，(2)在高电池电压下延长氧化还原电位，以及(3)高电化学可逆性以延长循环寿命。研究人员将利用研究成果作为推广活动的基础，与不同的学生和公众接触，以提高他们对可再生能源科学的理解，更广泛地说，是对可持续化学的理解。此外，建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，并将为本科生和研究生提供发展科学传播技能的机会。本项目旨在实现两个目标：(1)设计、合成并表征分子级、高氧化还原电位、无金属联吡啶和TTF衍生物的物理和氧化还原性质；(2)研究其在非水氧化还原液流电池（nrfb）中的应用，并利用原位循环伏安法以及操作紫外-可见和傅里叶变换红外光谱阐明其潜在的分解机制。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。这项研究将推动设计原理的前沿知识，指导具有高氧化还原电位、高电化学可逆性、增强的传质系数和高电子传递速率的氧化还原活性化合物的合成。本提案所做的工作将填补有前途的nrfb开发与缺乏理想氧化还原电解质之间的知识空白，并对理想氧化还原活性化合物产生关键的基础见解。本研究得出的结论将对电池性能增强设计产生深远的影响。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。

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.