Disordered rocksalt cathode materials for Na-ion Batteries

钠离子电池用无序岩盐正极材料

• 批准号: 2730040
• 金额: --
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2730040
• 关键词: Disordered; rocksalt; cathode; materials; Na

Disordered rocksalt cathode materials for Na-ion BatteriesThere is a pressing need to develop rechargeable batteries that are cheaper and more sustainable than the Li-ion battery. Na-ion offers an attractive alternative, but this technology falls short of Li-ion on performance, particularly energy density, due to a lack of suitable high energy Na-ion cathode materials. The key challenges are related to the fact that Na+ ions are larger than Li+. The increased size of Na+ induces changes in the host structure that are much more severe than Li+ when the ions are removed and reinserted, leading to degradation over cycling. There is also a limit to the amount of Na+ that can be incorporated into layered transition metal oxide hosts when they are synthesised, as they are too large to be substituted into sites in the transition metal layers. This means that the best cathodes typically only utilise a fraction of the Na+ ions that may be possible, thus restricting the energy density.This project aims to investigate a new class of Na-ion cathodes based on the disordered rocksalt crystal structure, following the recent discovery of several highly promising Li-ion analogues. The disordered nature of this structure permits the constraints on Na content to be relaxed, unlocking the possibility of synthesising "Na-rich" compositions with the potential to achieve higher energy densities than current state-of-the-art cathodes. The disordered rocksalt structure has also been shown to exhibit much less pronounced structural change during the charge-discharge reaction than in layered phases, allowing stable cycling over much wider compositional ranges. To make these phases, a range of synthetic approaches will be employed including mechanochemical ball-milling, in-situ electrochemical preparation and ion exchange. To understand the chemical and structural changes taking place during cycling, a range of advanced characterisation techniques will be employed, including diffraction, electron microscopy and spectroscopy. Diamond Light Source and ISIS neutron and muon source along with other international research facilities will also be used as part of this research to provide insight into the structural and electronic properties of these materials. The specific PhD thesis aims are: 1) to identify, synthesise and characterise new Na-ion disordered rocksalt compositions based on earth abundant elements, 2) to define the limits of synthetic viability of disordered rocksalt phases, 3) to develop a comprehensive understanding of the chemical and structural stability of these materials during charge and discharge in Na-ion cells, 4) to identify and optimise promising candidates for commercialisation in partnership with Faradion.This project falls within the EPSRC Energy Storage, Electrochemical Sciences and Materials for Energy applications research areas. It is part-funded by Faradion, the UK-based non-aqueous sodium-ion cell technology company.This is a 3.5-year EPSRC DTP-CASE studentship in association with Faradion Ltd.

用于钠离子电池的无序岩盐正极材料迫切需要开发比锂离子电池更便宜、更可持续的可充电电池。钠离子提供了一种有吸引力的替代方案，但由于缺乏合适的高能钠离子阴极材料，该技术在性能（特别是能量密度）方面低于锂离子。关键的挑战与 Na+ 离子比 Li+ 离子大有关。当离子被移除和重新插入时，Na+尺寸的增加会引起主体结构的变化，这种变化比Li+严重得多，从而导致循环过程中的降解。在合成层状过渡金属氧化物主体时，可以掺入层状过渡金属氧化物主体中的 Na+ 的量也受到限制，因为它们太大而无法取代过渡金属层中的位点。这意味着最好的阴极通常只利用可能的钠离子的一小部分，从而限制了能量密度。该项目旨在研究一种基于无序岩盐晶体结构的新型钠离子阴极，继最近发现了几种非常有前途的锂离子类似物之后。这种结构的无序性质允许放宽对钠含量的限制，释放了合成“富钠”组合物的可能性，该组合物有可能实现比当前最先进的阴极更高的能量密度。无序岩盐结构也被证明在充放电反应过程中表现出比层状相更不明显的结构变化，从而允许在更宽的组成范围内稳定循环。为了制备这些相，将采用一系列合成方法，包括机械化学球磨、原位电化学制备和离子交换。为了了解循环过程中发生的化学和结构变化，将采用一系列先进的表征技术，包括衍射、电子显微镜和光谱学。钻石光源、ISIS 中子和μ子源以及其他国际研究设施也将被用作这项研究的一部分，以深入了解这些材料的结构和电子特性。具体的博士论文目标是：1）基于地球丰富的元素识别、合成和表征新的钠离子无序岩盐组合物，2）定义无序岩盐相的合成可行性极限，3）全面了解这些材料在钠离子电池充电和放电过程中的化学和结构稳定性，4）与合作伙伴合作识别和优化有前景的商业化候选材料 Faradion。该项目属于 EPSRC 储能、电化学科学和能源应用材料研究领域。该项目由英国非水钠离子电池技术公司 Faradion 提供部分资助。这是与 Faradion Ltd 合作的 3.5 年 EPSRC DTP-CASE 学生奖学金。