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

电化学储能对于以可再生能源为主要动力的未来能源基础设施至关重要。目前，最先进的技术，锂离子电池，将无法充分满足日益增长的能量密度需求。在正在研究的新技术中，锂氧（Li-O2）电池是突出的，因为理论研究预测，锂氧电池可能比锂离子电池好2到10倍。迄今为止，电池电解质稳定性差是限制这项新技术进一步发展的关键因素。这个基础研究项目将直接解决这一关键挑战。该项目将研究一种含盐量高的水基电解质，使其在电池电极存在时不具有腐蚀性或反应性。通过这种方式，该项目将直接测试在电极上发生的关键反应，这些反应与预测相比限制了其整体性能。该研究项目随后将探索如何改进锂氧电池。该项目完成后，将推进这项有前途的新技术的研究。研究工作将辅以外联活动，旨在扩大可再生能源研究对不同受众的影响，包括本科生研究人员、高中生研究人员和上大学前的儿童及其家庭。该项目将为实现可再生能源驱动社会的目标做出重大贡献。本项目致力于解决锂- o2电池电解液降解问题的新策略的基础研究，该策略使用h2o基电解液，其中所有已知的电解液分解途径都被阻断。将使用高盐浓度的电解质（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液分解对现有锂氧电池低性能的影响。这些信息对于评价锂氧电池作为电化学储能技术的理论最大性能属性具有重要意义；然而，这方面的知识差距仍然存在。这一差距之所以存在，是因为之前对锂氧电池的研究都使用了对氧表现出反应性的电解质。因此，电解质分解导致的寄生化学反应无处不在，极大地破坏了旨在理解锂氧电池运行的努力。WiS电解质是一种超浓缩水溶液。当盐浓度足够高时（例如，21mol / 1kg H2O，或21m），所有H2O分子通过溶剂化盐离子而被锁定，并且整个溶液在一个相当宽的电位窗口内（例如，在1.9 V和4.9 V之间vs. Li/Li+）作为非质子溶液。这样的系统为研究锂氧电池的化学性质提供了一个独特的、无有机溶剂的环境。WiS电解质已被证明能够有效地为锂离子电池、锂硫电池以及最近的锂氧电池提供卓越的性能。该系统提供了一个独特的机会来检查锂氧电池的化学性质，而没有与电解质寄生化学反应相关的混淆因素。该项目的结果将是一个没有电解质分解等混杂因素的锂氧化学知识库。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。

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.