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长距离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+的离子半径比Li+大，Na离子阴极表现出更严重的结构转变。这限制了它们可以可逆循环的组成范围，导致较低的能量密度。尺寸差异的另一个结果是Na+离子通常太大而不能被取代到3d基层状氧化物阴极的过渡金属位点中，这意味着富Na阴极如Na2MnO3和Na1.2Ni0.2Mn0.6O2在合成上是不可行的。目前已知用作阴极的富钠材料主要有Na2RuO3和Na2IrO3，它们都含有价格昂贵的稀土金属，不适合大规模市场应用。本项目旨在探索新的合成路线来制备富钠过渡金属氧化物，以获得更高容量的钠离子阴极。在一种策略中，将选择在尺寸上更接近Na+（1.02 A）而不是Mn4+（0.53 A）的高价过渡金属离子，以有利于Na+离子在过渡金属层中的存在。这些将与低价过渡金属离子结合，作为电荷补偿氧化还原中心。另一种策略将涉及使用无序来获得富Na组合物。研究发现，具有d 0电子构型和零晶场稳定能的过渡金属离子（例如Ti 4+和Nb 5+）会促进富锂岩盐阴极中的阳离子无序。同样的原理将在钠离子系统中进行探索，以检验同样的效果是否转化为钠离子阴极以产生富钠材料。将使用一系列表征工具对所得材料进行研究，以确认结构、形态和组成，并验证每种策略的成功程度。它们将被用作钠离子电池的阴极材料，并将用衍射和光谱学研究充电和放电反应期间的结构和化学变化。一个特别的重点将支付给氧化物阴离子氧化还原的作用，预计在这些高程度的去钠丰富的materials.The材料和理解建立作为这个博士项目的结果将是重要的，在推进更高的能量密度钠离子电池的发展。这项技术可以提供一个可行的替代锂离子在廉价的，大众市场的电动汽车，并有助于侧步骤的问题，资源稀缺和价格波动，锂离子电池面临的。该项目属于EPSRC能源存储，电化学科学和材料的能源应用研究领域福尔斯。它完全由EPSRC资助。