Mixed Ion Electron Conductor (MIEC) Cascade Electrodes for High Density Energy Storage in Li2O2

锂（Li）-空气电池的潜在能量密度接近1，700 Wh/kg，是电动汽车和可再生能源存储的有前途的电池解决方案。此外，重量轻、体积小的能量存储对于广泛的移动的电源需求至关重要。该项目将描述一些与使用锂和氧之间的可逆反应储存能量相关的化学过程。锂空气电池系统有可能比类似容量的传统锂离子电池轻得多。目前的锂空气技术存在效率和能源容量低的问题。电池单元设计和操作条件可以以提高性能的方式进行修改，但是这些条件产生了许多新的复杂性，特别是在材料耐久性方面。该项目涉及使用固体材料的电池（与使用有机液体电解质的传统电池相反）。该研究将确定各种必要的固体-固体界面的化学性质和物理性质，这些界面可能会影响这种电池设计的可行性。该研究还将提供适用于传统锂离子电池更安全固态设计的材料的基础知识。在这个项目中还将开展几项教育推广工作。PI将参与当地社区学院教师的研究经验（RET）计划，让他们直接接触能源研究，并将相关概念纳入他们的课程。此外，还将提供一些本科生的研究实习机会，并将创建一系列与电池相关的教育网络模块。Li-O2电池因其高理论能量密度而受到关注。迄今为止，由于Li 2 O2产物的不良导电特性（导致自限放电）以及与电解质溶剂的寄生反应，这些装置仍然被认为是不实用的。该项目将探索与一种新方法相关的化学物质，通过调整操作条件和掺杂来提高Li 2 O2的电导率。该方法利用全固态单元架构。目前，在这些条件下的Li-O2氧化还原系统的生长机制和极化行为的知识很少。基础研究将表征电荷载流子迁移率，界面稳定性和掺杂剂化学，目的是了解如何设计基于Li-O2氧化还原的可逆能量密度存储系统。这项工作的一个关键方面是一个多方面的方法，用于表征相互作用的固体材料之间的“埋藏界面”，这是出了名的难以访问。该项目将利用原位XPS，阻抗谱和横截面像差校正电子显微镜的组合来表征这些界面的特性及其随时间，温度和极化的演变。虽然重点放在表征Li 2 O2和固体电化学材料之间的界面化学，但所研究的方法和系统将产生可转移到固态离子学中更广泛感兴趣的问题的见解，特别是在固态Li-该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准。

The lithium (Li)-air battery, with its potential energy density close to 1,700Wh/kg, is a promising battery solution for electric vehicles and renewable energy storage. In addition, light-weight and low-volume energy storage is crucial for a broad range of mobile power supply needs. This project will characterize a number of chemical processes that are relevant to storing energy using a reversible reaction between lithium and oxygen. The lithium-air battery system has the potential to be significantly lighter than conventional lithium-ion batteries of similar capacity. Current Li-air technology suffers from low efficiency and energy capacity. Battery cell design and operating conditions can be modified in ways to increase performance, but these conditions create a number of new complications, particularly with regard to materials durability. This project addresses a battery using solid materials (in contrast to conventional cells using organic liquid electrolytes). The research will determine the chemical nature and physical properties of various requisite solid-solid interfaces that can influence the viability of this battery design. The research will also provide fundamental knowledge of materials that are applicable to safer solid-state designs for conventional Li-ion batteries as well. Several educational outreach efforts will also be undertaken in this project. The PI will engage in a research experience for teachers (RET) program for local community college instructors for them to gain direct exposure to energy research and to incorporate related concepts into their curricula. Several undergraduate research internships will also be provided, and a series of educational web-modules related to batteries will be created.Li-O2 batteries have received recent attention due to their high theoretical energy density. To date these devices are still regarded as impractical due to the poor conducting character of the Li2O2 product (resulting in self-limiting discharge), as well as parasitic reactions with electrolyte solvents. This project will explore chemistries associated with a novel approach to raise the conductivity of Li2O2 through adjustments to operating conditions and doping. The approach utilizes an all-solid-state cell architecture. There is presently very little knowledge of the growth mechanisms and polarization behavior for the Li-O2 redox system under these conditions. The fundamental research will characterize charge carrier mobility, interfacial stability, and dopant chemistry with the aim of understanding how to engineer reversible, energy-dense storage systems based on Li-O2 redox. A key aspect of this work is a multi-faceted methodology for characterization of 'buried interfaces' between interacting solid materials, which are notoriously difficult to access. The project will utilize a combination of in-situ XPS, impedance spectroscopy, and cross-sectional aberration-corrected electron microscopy to characterize the properties of these interfaces and their evolution as a function of time, temperature, and polarization. While emphasis is placed on characterizing interfacial chemistries between Li2O2 and solid electrochemical materials, the methods and systems studied will yield insight that is transferrable to problems of broader interest in solid state ionics, particularly in the growing field of solid state Li-ion batteries.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.