Collaborative Research: Understanding ion solvation effects in nonaqueous oxygen electroreduction reactions

标题：合作研究：了解非水氧电还原反应中的离子溶剂化效应Bryan D.McCloskey/Venkatasubraman Viswanathan建议编号：1604927/1604898在目前正在探索的为下一代电动汽车提供动力的所有电池化学物质中，金属-空气(O2)对具有一些已知的最高理论比能量和体积能量密度。尤其是非质子非水Li-O2电池，由于其优越的比能量，最近受到了极大的关注。然而，Li-O2电池发展面临的许多挑战仍然没有解决。这些挑战之一涉及了解电解液组成和放电/充电电化学过程之间的联系。这项拟议的研究将解决Li-O2电化学机理对阳离子和阴离子溶剂化的根本依赖，从而更好地了解如何提高高能非水Li-O2电池和其他金属-O2电池的性能。如果成功，Li-O2电池可以推进和加速电动汽车的采用，以减少排放，提高能效，并确保国内能源安全。私人投资促进机构致力于广泛传播其结果。因此，他们将开发在线视频模块，使公众能够了解这一令人兴奋的新能源储存领域的前景。在线模块的结构将简单地纳入能源和电化学系统课程，包括由私人投资机构教授的课程。投资促进机构还将开发更广泛和更吸引人的关于电化学/电池的教育内容，以期开办一个大规模的在线公开课程。这项研究的总体目标是阐明离子溶剂化对非水电解液中基氧电化学的影响，特别是在含Li+的电解液中的氧还原。最近的研究已经确认了电解液组成对最终形成的氧还原产物及其形成机理的重要性。例如，在非水Li-O2电池中发现发生2e-氧还原形成过氧化锂Li2O2，而在Na-O2电池中发生1e-还原过程形成超氧化物钠NaO2。此外，Li-O2的放电机理最近被证明受到阴离子和溶剂选择之间微妙的相互作用的影响，因为这两个组分的Lewis酸碱性都影响了氧还原中间体在溶液中的寿命。PI利用这一知识将锂-O2电池的放电容量(或可用能量)提高了四倍。然而，对电解液成分(离子、添加剂和溶剂)对电极反应和离子溶剂化的复杂作用的了解还不完全。这一理解可能对许多其他电化学系统(如二氧化碳减排、锂-S电池和其他金属-空气电池)具有深远的影响。拟议的研究任务将利用PI开发的独特实验和理论能力来研究Li-O2电池，包括差示电化学质谱仪(DEM)来量化采用不同电解液成分的电池的库仑效率，以及核磁共振光谱来探测这些电解液中的阳离子和阴离子溶剂化。描述非平衡电荷传输以及溶液和表面电化学的理论能力将基于密度泛函理论计算。通过完善的理论和实验框架，PI将确定能够触发溶液电化学的新型电解液成分，从而在保持化学稳定性的同时提高放电容量。然后，PI将在实验上将最有希望的电解液组合物中的离子溶剂化效应与稳定性和容量增强联系起来。

Title: Collaborative Research: Understanding Ion Solvation Effects in Nonaqueous Oxygen Electroreduction ReactionsBryan D. McCloskey/ Venkatasubraman ViswanathanProposal Number: 1604927/1604898Of all battery chemistries currently being explored to power next-generation electric vehicles, metal-air (O2) couples possess some of the highest known theoretical specific energies and volumetric energy densities. In particular, the aprotic nonaqueous Li-O2 battery has recently received significant attention because of its superior specific energy. Yet many of the challenges facing Li-O2 battery development remain unsolved. One of these challenges involves understanding the link between electrolyte composition and the discharge/charge electrochemical processes. The proposed research will address the fundamental dependence of the Li-O2 electrochemistry mechanism on both cation and anion solvation, thereby providing a better understanding of how to improve the performance of high-energy nonaqueous Li-O2 and other metal-O2 batteries. If successful, Li-O2 batteries could advance and accelerate the adoption of electric vehicles for reduced emissions, improved efficiency, and domestic energy security. The PIs are committed to broad dissemination of their results. As such, they will develop online video modules to make publicly accessible the prospects of this exciting new area of energy storage. The online modules will be structured for simple incorporation into energy and electrochemical system courses, including those taught by the PIs. The PIs will also develop a broader and more engaging educational content on electrochemistry/batteries with a vision to run a massive online open course. The overall objective of the proposed research is to elucidate the effect of ion solvation on the fundamental oxygen electrochemistry in nonaqueous electrolytes, with a particular emphasis on oxygen reduction in Li+-bearing electrolytes. Recent studies have identified the importance of electrolyte composition on both the ultimate oxygen reduction product formed and the mechanism by which it forms. For example, a 2 e- oxygen reduction to form lithium peroxide, Li2O2, is found to occur in nonaqueous Li-O2 batteries, whereas a 1 e- reduction process to form sodium superoxide, NaO2, occurs in Na-O2 batteries. Furthermore, the Li-O2 discharge mechanism was recently shown to be affected by a delicate interplay between anion and solvent selection, as the Lewis acidity and basicity of both components affected the lifetime of oxygen reduction intermediates in solution. The PIs used this knowledge to improve the discharge capacity (or usable energy) of a Li-O2 battery four-fold. However, the understanding of the complex role of electrolyte constituents (ions, additives, and solvents) on electrode reactions and ion solvation is not complete. This understanding potentially has far-reaching implications in many other electrochemical systems (e.g., CO2 reduction, Li-S batteries, and other metal-air batteries). The proposed research tasks will leverage unique experimental and theoretical capabilities developed by the PIs to study Li-O2 batteries, including Differential Electrochemical Mass Spectrometry (DEMS) to quantify Coulombic efficiency of batteries employing different electrolyte compositions, and nuclear magnetic resonance spectroscopy to probe cation and anion solvation in these electrolytes. The theoretical capabilities to describe non-equilibrium charge transport, and solution and surface electrochemistry, will be based on density functional theory calculations. Through a well-developed theoretical and experimental framework, the PIs will identify novel electrolyte compositions that can trigger solution electrochemistry, thereby improving discharge capacity while maintaining chemical stability. The PIs will then experimentally link ion solvation effects in the most promising electrolyte compositions to stability and capacity enhancements.