Advanced Electrochemistry of Na-ion Battery Cathodes Through Chemically Controlled Materials Synthesis

摘要插层反应是锂离子电池运行机制的核心，锂离子电池是便携式电子设备和电动汽车中使用最多的储能装置。插入通常是一个可逆过程，涉及将客体物质引入主电极材料。认识到锂是一种有限的资源，这可能会导致锂离子电池成本的显著增加，研究方向已经转向研究替代插层系统，如钠离子电池。然而，与锂离子相比，更大的尺寸和更高的重量限制了钠离子通过普通电极材料的插入和扩散。这将导致显著的电极退化（从而导致第一次循环后的容量损失和循环寿命缩短），并限制在高电流速率下的操作。在材料研究部固态与材料化学项目的支持下，该项目致力于通过化学预插特定类型和数量的无机离子来解决这些缺点。提出的工作有可能使钠离子电池阴极的发展成为可能，可用于取代目前的锂离子电池，提供更便宜、可靠、环保的可持续能源存储，有助于下一代交通、电网存储和其他可再生能源应用的能源存储系统的发展。该项目提供了一个极好的机会，让大四本科生和研究生参与材料科学与工程领域的硕士和博士水平的研究，并对材料化学和电化学产生更广泛的影响。首席研究员计划将这项研究成果整合到能源存储应用材料课程中。该项目通过在国家/国际会议上发表演讲、在期刊出版物上发表评论和在科学活动上进行示范，加强向广泛的研究界和一般公众传播知识。化学预插层是一种湿化学方法，其中无机离子被插入到溶液中电极材料的晶体结构中，随后形成凝胶和/或溶胶，或其他形式的沉淀物，无机离子被“捕获”在固体材料的结构中。本研究的目的是验证一个假设，即通过引入特定类型和数量的化学预插离子，可以在na离子电池电极中实现高容量、长循环寿命和高功率，从而使材料具有高比容量、增强结构稳定性和快速离子扩散。氧化钒是一种具有丰富晶体化学性质、结构柔韧性和形态结构的材料，被选择作为化学预插层的主体结构。该项目寻求对钠离子电池中化学预插层氧化钒电极的合成-结构-性能关系的系统理解。通过循环伏安法、恒流放电/充电循环、速率性能实验和阻抗谱测量等方法对合成材料的电化学性能进行了评价。研究小组计划确定合成参数的变化如何影响电化学性能，目的是了解与材料化学和结构相关的基本现象，这些现象可能导致更多的存储电荷，更快的离子和电子传输，以及钠离子可逆循环过程中的优异稳定性。

Non-Technical AbstractIntercalation reactions lie at the heart of the operation mechanism of lithium-ion battery, which remains the most used energy storage device for portable electronics and electric cars. Intercalation is usually a reversible process that involves the introduction of a guest species into a host electrode material. The realization that lithium is a limited resource, which potentially can result in a significant increase in the cost of lithium-ion batteries, has shifted research directions towards investigation of alternate intercalation systems, such as sodium-ion batteries. However the larger size and higher weight limits intercalation and diffusion of sodium ions through common electrode materials, compared to lithium ion. This results in significant electrode degradation (thereby resulting in capacity loss after the first cycle and reduced cycle life) and limitations in operation at high current rates. With support from the Solid State and Materials Chemistry program of the Division of Materials Research, this project focuses on addressing these shortcomings through chemical pre-intercalation of the specific types and amounts of inorganic ions. The proposed work has the potential to enable the development of sodium-ion battery cathodes that can be used to replace current lithium-ion batteries, providing sustainable energy storage that is cheaper, reliable, and environmentally friendly, contributing to the development of next-generation energy storage systems for transportation, grid-storage and other renewable energy applications. The project offers an excellent opportunity to engage senior undergraduate and graduate students in masters and doctoral-level research in the field of Materials Science and Engineering and its broader impact on Materials Chemistry and Electrochemistry. The principal investigator plans to integrate the results of this research in the course on materials for energy storage applications. This project enhances the dissemination of knowledge to a broad research community and general public through presentations at National/International conferences, refereed journal publications and demonstrations at science events.Technical AbstractChemical pre-intercalation is a wet chemistry approach, in which the inorganic ions are inserted into the crystal structure of the electrode material in a solution followed by the formation of a gel and/or sol, or another form of a precipitate, with inorganic ions being 'trapped' in the structure of a solid material. The goal of this proposed research is to test the hypothesis that high capacity, long cycle life and high power can be achieved in Na-ion battery electrodes by introducing specific types and amounts of chemically pre-intercalated ions, which enables materials with high specific capacity, enhanced structural stability and fast ionic diffusion. Vanadium oxide, a material with rich crystal chemistry, structural flexibility and morphological architectures, is chosen as a host structure for chemical pre-intercalation. The project seeks a systematic understanding of synthesis - structure - performance relationships for chemically pre-intercalated vanadium oxide electrodes in Na-ion batteries. Electrochemical properties of the synthesized materials are evaluated by cyclic voltammetry, galvanostatic discharge/charge cycling, rate capability experiments and impedance spectroscopy measurements. The research team plans to determine how changes in the synthesis parameters affect electrochemical performance with the aim to understand fundamental phenomena related to materials chemistry and structure that may lead to larger amount of the stored charge, faster ion and electron transport, and excellent stability during reversible cycling of sodium ions.