Probing ionic diffusion in battery materials using NMR

该项目属于EPSRC物理科学和能源研究领域。对更好的电池的需求从未像现在这样强烈。由于其高能量密度，锂离子电池已经给消费电子产品带来了革命性的变化，并在交通电气化中发挥着核心作用。为了支持向可再生能源的过渡，以及随着汽车行业完全电动，将需要新的高性能材料。为了满足这一需求，锂离子电池需要使用新材料，同时也需要开发新技术，如全固态电池。例如，固体电解质使锂金属阳极的使用成为可能，显著增加了能量密度。了解这些材料中的离子扩散是调整成分、开发新材料和实现新电池技术的关键。由于在任何一种材料中，离子传输跨越了大范围的时间和长度尺度，因此开发一幅全面的离子传输物理图景是具有挑战性的。离子输运分为微观和宏观两个层次，其中宏观过程由一系列微观事件组成。变温核磁共振谱和核磁共振弛豫法可以探测微观过程，但这些技术不能考察锂的长程扩散。脉冲梯度场(PFG)核磁共振技术可以测量宏观离子在固体材料中的扩散。PFG是特定于原子核的，因此可以提供关于每个离子贡献的信息。这项技术对电化学阻抗谱(EIS)具有很高的信息量和互补性。当PFG和EIS成功地结合使用时，可以估计可移动离子的浓度。该项目将涉及技术开发，使数据收集和分析能够在一系列电池材料上进行。PFG核磁共振将用于测量扩散系数、活化能和估计一系列重要电池材料的电导率，如固体电解液。除了核磁共振，还将使用一些实验技术来提供补充数据。电化学循环和技术，如交流阻抗谱，将被用于研究性能。包括衍射、显微镜和断层扫描在内的技术将提供额外的结构数据来支持模型。该项目由约翰逊·马泰共同资助，作为iCASE学生项目的一部分。

This project falls within the EPSRC Physical Sciences and Energy research areas.The need for better batteries has never been greater. Due to their high energy densities, lithium ion batteries have revolutionised consumer electronics and are playing a central role in the electrification of transport. In order to support the transition to renewable energy sources and as the automotive sector becomes fully electric, new high-performing materials will be needed. In order to meet this demand, new materials are required for use in Li-ion cells but also for the development of new technologies such as all solid-state batteries. For example, solid electrolytes make the use of a lithium metal anode possible, significantly increasing the energy density. Understanding ionic diffusion in these materials is key to tuning compositions, developing new materials and enabling new battery technologies. The development of a comprehensive physical picture of ion transport is challenging because in any one material ion transport crosses a large range of time and length scales. Ion transport is divided into microscopic and macroscopic levels, where the macroscopic processes consist of a series of microscopic events. Microscopic processes can be probed using variable-temperature nuclear magnetic resonance spectroscopy (NMR) and NMR relaxometry, however, these techniques are unable to review the long-range lithium diffusion. Pulsed-field gradient (PFG) NMR allows the measurement of macroscopic ionic diffusion through solid materials. PFG is nuclei specific and can therefore provide information about each of the ion's contributions. This technique is highly informative and complementary to Electrochemical Impedance Spectroscopy (EIS). When PFG and EIS can be used successfully in tandem, the mobile ion concentration can be estimated.This project will involve technique development to enable data collection and analysis to be carried out on a range of battery materials. PFG NMR will be used to measure diffusion coefficients, activation energies and estimate conductivities of a range of important battery materials, such as solid electrolytes. Alongside NMR, a number experimental techniques will be used to provide complementary data. Electrochemical cycling and techniques, such as EIS, will be used to investigate performance. Techniques, including diffraction, microscopy and tomography will provide additional structural data to support models.The project is co-funded by Johnson Matthey as part of an iCASE studentship.