Collaborative Research: Elucidating Correlations Between Solvation Structure and Electrochemical Behavior of Water-in-Salt Electrolytes for Highly Reversible Zinc Metal Anode

风能和太阳能的可再生能源为减少温室气体排放及其对气候变化的影响提供了一种解决方案。不幸的是，这些可再生能源产生的电力是间歇性的，通常与电能需求不同步。因此，大规模的能源储存对于减少对化石燃料的依赖的可持续经济是不可或缺的。含水锌(锌)金属电池能够以低成本、低环境足迹和高固有安全性来存储能量，是解决这一能量存储需求的一种有前途的解决方案。然而，锌金属电池的循环寿命较短，这主要是由于水对锌金属负极的腐蚀。这种腐蚀极大地缩短了锌金属电池的循环寿命，并由于产生爆炸性氢气而引起安全问题-这两个挑战需要开箱即用的解决方案。最近出现的高度浓缩的“盐中水”电解液为重新定义锌金属阳极和水电解液之间的稳定性提供了一个独特的机会。本项目旨在改变锌水电池的循环稳定性，提高电池的安全运行。如果成功，这将标志着美国储能技术的重大突破。在教育影响方面，调查人员将利用他们所在大学的机构项目，增加社区大学生和高中生参与暑期研究体验。研究生和本科生的培训将满足下一代能源部门的劳动力需求。该项目将通过整合材料电化学、飞秒拉曼光谱和从头计算方面的研究活动，阐明高度浓缩溶液中的水稳定性性质。这些互补的方法是高度协同的，提供了来自不同优势点的见解，当整合在一起时，可以实现深入的理解。在所研究的浓缩电解液中，每个溶剂化离子中的水分子很少；因此，与标准稀溶液相比，溶剂化离子鞘通常较薄或不完整。这种溶剂化结构显著改变了溶剂化离子和作为溶剂的动态水分子的性质。初步结果表明，水分子表现出对放氢异常高的电化学稳定性，并在受激拉曼研究中显示出有趣的振动频率蓝移。第一性原理计算表明，在这些浓溶液中存在着需要探索的水分子的特殊性质。该项目将深入了解浓缩电解液的溶剂化结构与与锌金属阳极接触的相应稳定性之间的关系。这些知识的价值将超越物理科学和工程的不同学科，并影响学术和工业环境中广泛的STEM学习者和实践者。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 from wind energy and solar power offers a solution to reducing greenhouse gas emissions and their impact on climate change. Unfortunately, the power that can be generated from these renewable sources is intermittent and typically asynchronous with electrical energy demand. Thus, large-scale energy storage is indispensable for a sustainable economy with reduced reliance on fossil fuels. Representing a promising solution to this energy storage need, aqueous zinc (Zn) metal batteries can store energy at a low cost, with low environmental footprint and high intrinsic safety. However, Zn metal batteries suffer from short cycle life, primarily due to corrosion of the Zn metal anode by water. This corrosion drastically curtails the cycle life of Zn metal batteries and causes a safety concern due to the generation of explosive hydrogen gas—two challenges that require outside-the-box solutions. The recent emergence of highly concentrated “water-in-salt” electrolytes offers a unique opportunity to re-define the stability between the Zn metal anode and the aqueous electrolyte. This project seeks to transform the cyclic stability and increase safe operation of aqueous Zn metal batteries. If successful, this will mark a significant breakthrough for energy storage technologies in the United States. For educational impacts, the investigators will leverage institutional programs their universities to increase the participation of community college students and high school students in summer research experiences. The training of graduate and undergraduate students will feed the workforce need of the next-generation energy sector.The project will elucidate the water stability properties in extremely concentrated solutions by integrating research activities in materials electrochemistry, femtosecond Raman spectroscopy, and ab initio computation. These complementary methods are highly synergistic, providing insights from different vantage points that when integrated can enable deep understanding. In the concentrated electrolytes of study there are few water molecules per solvated ion; therefore, the solvation sheaths are often thinner or incomplete compared to standard dilute solutions. Such solvation structures significantly alter the properties of the solvated ions and the dynamic water molecules as a solvent. Preliminary results have revealed that water molecules exhibit unusually high electrochemical stability against hydrogen evolution and display an intriguing blueshift of vibrational frequencies in stimulated Raman studies. First-principles calculations indicate that there exist peculiar properties of water molecules to be explored in these concentrated solutions. This project will generate an in-depth understanding of the correlation between solvation structures of the concentrated electrolytes and the corresponding stability in contact with the Zn metal anode. The values of such knowledge will transcend different disciplines of physical sciences and engineering and impact a broad range of STEM learners and practitioners in academic and industrial settings.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.