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

插层反应是锂离子电池工作机理的核心，锂离子电池仍然是便携式电子产品和电动汽车最常用的储能设备。插层通常是一个可逆的过程，包括将客体物种引入到宿主电极材料中。人们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，这使得研究方向转向研究替代嵌入系统，如钠离子电池。然而，与锂离子相比，较大的尺寸和较高的重量限制了钠离子在普通电极材料中的嵌入和扩散。这导致电极严重退化(从而导致第一次循环后的容量损失和循环寿命缩短)，并限制了在高电流速率下的运行。在材料研究部固态和材料化学计划的支持下，该项目专注于通过对特定类型和数量的无机离子进行化学预嵌插来解决这些缺点。拟议的工作有可能使开发可用于取代当前锂离子电池的钠离子电池阴极成为可能，提供更便宜、更可靠、更环保的可持续能量存储，有助于开发用于交通、电网存储和其他可再生能源应用的下一代能量存储系统。该项目提供了一个极好的机会，让高年级本科生和研究生参与材料科学和工程领域的硕士和博士水平的研究，以及它对材料化学和电化学的更广泛影响。首席研究员计划将这项研究的结果纳入关于储能应用材料的课程。该项目通过在国内/国际会议上的演讲、被引用的期刊出版物和在科学活动上的演示，加强向广大研究社区和公众传播知识。技术摘要化学预插层是一种湿化学方法，将无机离子插入到溶液中的电极材料的晶体结构中，然后形成凝胶和/或溶胶，或另一种形式的沉淀物，无机离子被‘捕获’在固体材料的结构中。这项研究的目的是通过引入特定类型和数量的化学预嵌离子来检验钠离子电池电极可以实现高容量、长循环寿命和高功率的假设，从而使材料具有高比容量、增强的结构稳定性和快速的离子扩散。氧化钒作为化学预插层的主体结构，具有丰富的晶体化学组成、结构灵活性和形态构型。该项目旨在系统地了解钠离子电池中化学预嵌氧化钒电极的合成-结构-性能关系。通过循环伏安、恒电流放电/充电循环、倍率容量实验和交流阻抗谱测试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，以期了解与材料化学和结构相关的基本现象，这些现象可能导致钠离子在可逆循环过程中存储更多的电荷、更快的离子和电子传输以及良好的稳定性。

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.