Characterizing the Behaviors of Li-O2 Battery in a Stable Electrolyte System

电化学能量存储对于主要由可再生能源供电的未来能源基础设施至关重要。目前，最先进的技术，锂（Li）离子电池，将不足以满足能量密度方面日益增长的需求。在正在追求的新技术中，锂氧（Li-O2）电池是突出的，因为理论研究预测Li-O2电池可能比锂离子电池好2到10倍。到目前为止，电池电解液的稳定性差是限制这项新技术进一步发展的关键因素。这项基础研究项目将直接解决这一关键挑战。 该项目将研究一种具有高盐含量的水基电解质，使其在电池电极存在时不会腐蚀或反应。通过这种方式，该项目将直接测试与预测相比，电极上发生的限制其整体性能的关键反应。该研究项目将探索如何改进Li-O2电池。 该项目完成后，将推动对这一有前途的新技术的研究。 研究工作将辅之以旨在扩大可再生能源研究的影响，以不同的受众，包括本科生研究人员，高中生研究人员和大学前儿童及其家庭的外联活动。 本项目将对实现可再生能源社会的目标做出重要贡献。本项目旨在通过使用H2O系电解液，阻断所有已知的电解液分解途径，解决锂氧电池电解液降解问题的新策略的基础研究。将使用具有高盐浓度的电解质（称为盐中水，WiS），以最大限度地减少H2O分解和H2O诱导的氧化物分解的潜在负面影响。该项目的研究目标是定量研究电解质分解如何导致现有Li-O2电池的低性能。 该信息对于评估Li-O2电池作为电化学能量存储技术的理论最大性能属性是必不可少的;然而，对于该信息存在知识缺口。差距的存在是因为以前对Li-O2电池的研究都采用了对氧物种表现出反应性的电解质。 因此，由于电解质分解引起的寄生化学反应无处不在，大大破坏了旨在了解Li-O2电池操作的努力。 WiS电解质代表超浓缩水溶液。 当盐浓度足够高时（例如，21摩尔/1千克H2O，或21摩尔）时，所有H2O分子通过溶解盐离子而被锁定，并且整个溶液在合理宽的电势窗口内充当非质子溶液（例如，相对于Li/Li+在1.9 V和4.9 V之间）。 这种系统为Li-O2电池化学研究提供了独特的无有机溶剂环境。 WiS电解质已被证明能有效地为锂离子电池、锂硫电池以及最近的锂氧电池提供上级性能。 该系统提供了一个独特的机会来检查锂氧电池化学，而没有与电解质的寄生化学反应有关的混淆因素。 该项目的成果将是一个没有电解质分解等混杂因素的Li-O2化学知识库。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。

Electrochemical energy storage is of paramount importance to a future energy infrastructure that is primarily powered by renewable sources. Currently, the state-of-the-art technology, lithium (Li)-ion batteries, will not sufficiently meet increasing needs in terms of energy densities. Of the new technologies that are being pursued, lithium-oxygen (Li-O2) batteries are prominent as theoretical studies predict that Li-O2 batteries could be 2 to 10 times better than Li-ion batteries. To date, the poor stability of the battery electrolyte is a key factor that limits further advancement of this new technology. This fundamental research project will directly address this critical challenge. This project will research a water-based electrolyte that has a high level of salt so that it is not corrosive or reactive in the presence of the battery electrodes. In this way the project will directly test what key reactions occur at the electrode that limit its overall performance compared to predictions. The research project will then explore how to improve Li-O2 batteries. Upon its completion, the project will advance research on this new promising technology. The research efforts will be complemented by outreach activities designed to broaden the impacts of renewable energy research to diverse audiences including undergraduate researchers, high school student researchers, and pre-college children and their families. The project will contribute significantly to the goals of moving toward a renewable energy-powered society.This project addresses fundamental research on a novel strategy to solve the problem of electrolyte degradation of lithium-O2 batteries by using a H2O-based electrolyte, in which all known electrolyte decomposition pathways are blocked. An electrolyte with high salt concentration (referred to as water in salt, WiS) will be used to minimize potential negative influences by H2O decomposition and H2O-induced oxide decomposition. The project's research goal is to quantitatively study how electrolyte decomposition contributes to the low performance of existing Li-O2 batteries. This information is imperative to the evaluation of the theoretical maximum performance attribute of Li-O2 battery as an electrochemical energy storage technology; however, a knowledge gap exists for this information. The gap exists because previous research on Li-O2 batteries all employed electrolytes that exhibit reactivity toward oxygen species. As a result, parasitic chemical reactions due to electrolyte decomposition have been ubiquitous, greatly undermining efforts designed to understand Li-O2 battery operations. The WiS electrolyte represents a super-concentrated aqueous solution. When the salt concentration is sufficiently high (e.g., 21 mole/1 kg of H2O, or 21 m), all H2O molecules are locked down by solvating the salt ions, and the overall solution acts as an aprotic one within a reasonably wide potential window (e.g., between 1.9 V and 4.9 V vs. Li/Li+). Such a system provides a unique, organic-solvent-free environment for the studies of Li-O2 battery chemistries. WiS electrolytes have proven effective in enabling superior performance for Li-ion, Li-sulfur and, most recently, Li-O2 battery operations. The system provides a unique opportunity to examine Li-O2 battery chemistry without the confounding factors connected to parasitic chemical reactions of the electrolytes. The outcome of the project will be a knowledge base of Li-O2 chemistry without the confounding factors such as electrolyte decomposition.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.