Earth-abundant Cathodes for Na-ion Batteries

地球储量丰富的钠离子电池阴极

• 批准号: 2733506
• 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-2733506
• 关键词: Earth; abundant; Cathodes; Na; ion

Sodium-ion batteries are considered to be a main contender to lithium-ion as they are cheaper and made from more abundant, sustainable materials. However, Na-ion batteries cannot currently deliver the high volumetric and gravimetric energy densities that are required for long-range electric vehicles. A key constraint is the cathode. Due to the larger ionic radius of Na+ compared with Li+, Na-ion cathodes exhibit more severe structural transitions. This limits the compositional range over which they can be cycled reversibly leading to lower energy density. Another consequence of the difference in size is that Na+ ions are typically too large to be substituted into the transition metal sites of 3d-based layered oxide cathodes, meaning Na-rich cathodes such as Na2MnO3 and Na1.2Ni0.2Mn0.6O2 are not synthetically viable. The primary known examples of Na-rich materials which have been used as cathodes, Na2RuO3 and Na2IrO3, involve expensive rare earth metals which are not suitable for mass market application.This project aims to explore new synthetic routes to make Na-rich transition metal oxides in order to achieve Na-ion cathodes with higher capacities. In one strategy, high valence transition metal ions which are closer in size to Na+ (1.02 A) than Mn4+ (0.53 A) will be selected to favour the presence of Na+ ions in the transition metal layer. These will be combined with low valence, transition metal ions to act as charge compensating redox centres. Another strategy will involve using disorder to access Na-rich compositions. Transition metal ions such as Ti4+ and Nb5+ with d0 electron configurations and zero crystal field stabilisation energy are found to promote cation disorder in Li-rich rocksalt cathodes. This same principle will be explored in Na-ion systems to examine whether the same effect translates to Na-ion cathodes to yield Na-rich materials.To make these phases, conventional solid state synthesis under different atmospheres and temperature regimes will be explored. The resulting materials will be investigated with a range of characterisation tools to confirm structure, morphology and composition and verify the extent of success of each strategy. They will be examined as cathode materials in Na-ion cells and the structural and chemical changes during the charge and discharge reactions will be studied with diffraction and spectroscopy. A particular focus will be paid to the role of oxide anion redox which is anticipated at high degrees of desodiation in these Na-rich materials.The materials and understanding established as a result of this PhD project will be important in advancing the development of higher energy density Na-ion batteries. This technology could provide a viable alternative to Li-ion in cheap, mass market electric vehicles and help to side-step the issues of resource scarcity and price volatility that Li-ion batteries face.This project falls within the EPSRC Energy Storage, Electrochemical Sciences and Materials for Energy applications research areas. It is fully funded by the EPSRC.

钠离子电池被认为是锂离子电池的主要竞争者，因为它们更便宜并且由更丰富、可持续的材料制成。然而，钠离子电池目前无法提供远程电动汽车所需的高体积和重量能量密度。一个关键的限制是阴极。由于Na+与Li+相比离子半径更大，因此Na离子阴极表现出更严重的结构转变。这限制了它们可逆循环的成分范围，导致能量密度降低。尺寸差异的另一个后果是 Na+ 离子通常太大而无法取代 3d 基层状氧化物阴极的过渡金属位点，这意味着 Na2MnO3 和 Na1.2Ni0.2Mn0.6O2 等富钠阴极在合成上不可行。已知用作正极的富钠材料的主要例子是Na2RuO3和Na2IrO3，涉及昂贵的稀土金属，不适合大众市场应用。该项目旨在探索新的合成路线来制造富钠过渡金属氧化物，以实现具有更高容量的钠离子正极。在一种策略中，将选择尺寸更接近Na+(1.02A)而不是Mn4+(0.53A)的高价过渡金属离子，以有利于过渡金属层中Na+离子的存在。这些将与低价过渡金属离子结合，充当电荷补偿氧化还原中心。另一种策略将涉及利用无序来获取富含钠的成分。研究发现，具有 d0 电子构型和零晶体场稳定能的过渡金属离子（例如 Ti4+ 和 Nb5+）会促进富锂岩盐阴极中的阳离子无序。我们将在钠离子系统中探索相同的原理，以检查相同的效果是否转化为钠离子阴极以产生富钠材料。为了制备这些相，将探索不同气氛和温度条件下的常规固态合成。将使用一系列表征工具对所得材料进行研究，以确认结构、形态和成分，并验证每种策略的成功程度。它们将作为钠离子电池的阴极材料进行检查，并通过衍射和光谱研究充电和放电反应过程中的结构和化学变化。我们将特别关注氧化物阴离子氧化还原的作用，预计这些富钠材料会在高度脱钠的情况下发挥作用。该博士项目所建立的材料和理解对于推进更高能量密度钠离子电池的开发非常重要。该技术可以为廉价的大众市场电动汽车提供锂离子电池的可行替代品，并有助于回避锂离子电池面临的资源稀缺和价格波动问题。该项目属于 EPSRC 储能、电化学科学和能源应用材料研究领域。它由 EPSRC 全额资助。