Materials chemistry and electrochemistry of O-redox cathode materials

该项目属于EPSRC物理科学和能源研究领域。上个世纪锂离子电池的发明给便携式电子产品带来了革命性的变化，现在它们在应对气候变化的努力中发挥着关键作用。除了在消费电子产品中的应用外，它们现在还支持将可再生能源整合到电网中，并过渡到电动汽车。随着对电池依赖的增加，人们对更高的能量密度、更安全和更便宜的材料有了更高的需求。正极是提高锂离子电池能量密度的最大障碍之一。目前，大多数锂电池都含有过渡金属氧化物正极，含有镍、锰和钴。钴的使用存在供应和伦理问题，人们希望减少正极材料中使用的钴的量。另一个挑战是通过寻找新的阴极材料来提高能量密度--这将增加电动汽车的续航里程。近年来，出现了一类新的正极材料，它们有可能显着提高锂离子电池的能量密度。这些材料的容量超过了基于过渡金属氧化还原的预期容量，而且已经表明，额外的容量来自于氧化物离子上电荷的储存。这被称为阴离子氧化还原，并在许多材料中观察到。这些材料很有希望成为下一代正极材料的候选材料，但要实现它们的实际应用，必须解决许多挑战，包括氧损失、动力学缓慢和结构不稳定。本项目将研究阴离子氧化还原的基本过程，以解决这些问题并指导材料的发现。有望显示阴离子氧化还原的新材料将被合成。理想情况下，这些材料将显示有限的电压降、滞后和容量衰减。将进行表征，以了解自行车在骑行过程中发生的结构变化。这将涉及对现有技术的修改和新技术的开发。关于这些变化如何和为什么发生的知识将被用来制定设计新材料的战略，例如调整成分。研究方法将涉及一些合成技术，包括共沉淀、水热和固态。将使用广泛的表征技术来研究在循环过程中发生的结构和电子变化。包括衍射、核磁共振光谱和电子显微镜在内的技术将被用来研究结构变化。将使用国家和国际设施进行异地和操作测量，并将使用共振非弹性X射线散射和X射线吸收散射等技术来研究电子变化。

This project falls within the EPSRC Physical Sciences and Energy research areas.The invention of lithium ion batteries in the last century revolutionised portable electronics and they are now playing a key role in efforts to combat climate change. In addition to their use in consumer electronics, they are now supporting the integration of renewables into the electricity grid and the transition to electric vehicles. As dependence on batteries grows there is a demand for higher energy density, safer and cheaper materials. The cathode represents one of the greatest barriers to increasing the energy density of lithium ion batteries.Currently most lithium batteries contain a transition metal oxide cathode, containing Ni, Mn and Co. There are supply and ethical issues surrounding the use of cobalt and there is a desire to reduce the amount of cobalt used in cathode materials. Another challenge is to increase the energy density by finding new cathode materials - this would increase the range of an electric vehicle. In recent years a new class of cathode materials have emerged that have the potential to significantly increase the energy density of lithium ion cells. These materials exhibit capacities beyond those expected based on transition metal redox and it has been shown that the additional capacity comes from the storage of charge on oxide ions. This has been termed anionic redox and has been observed in a number of materials. These materials are promising candidates for the next generation of cathode materials but there are number of challenges that must be addressed to realise their practical application, including oxygen loss, slow kinetics and structural instability.This project will investigate the fundamental processes underlying anionic redox to tackle these problems and direct materials discovery. New materials which are expected to show anionic redox will be synthesised. These materials will ideally show limited voltage drop, hysteresis and capacity fade. Characterisation will be carried out to understand the structural changes taking place during cycling. This will involve the modification of existing and development of new tecnhiques. The knowledge of how and why these changes occur will be used to devise strategies for designing new materials, e.g. tuning composition.The research methodology will involve a number of synthetic techniques, including co-precipitation, hydrothermal and solid-state. A wide range of characterisation techniques will be used to investigate the structural and electronic changes that occur during cycling. Techniques including diffraction, nuclear magnetic resonance spectroscopy and electron microscopy will be used to study structural changes. National and international facilities will be used to carry out ex-situ and operando measurements and techniques such as resonant inelastic X-ray scattering and X-ray absorption scattering will be used to investigate electronic changes.