Single-particle electrochemistry to identify fundamental barriers to magnesium ion intercalation in transition metal oxides

在过去的几年里，锂离子电池在可实现的储能容量和耐用性方面稳步增长，使其成为主导市场的参与者。然而，加快向以可再生能源为基础的社会过渡仍然需要新的替代电池化学物质。一种可能的解决方案是用镁等多价载体取代锂离子作为电子电荷的主要载体。使用镁的理论收益受到相关工作温度下镁在电池内的低效传输的阻碍，特别是在能量密度转换收益所需的固体氧化物阴极中。在这个项目中，结合了新的电子显微镜方法来检测模型过渡金属氧化物作为镁离子电池正极的本征反应性。这些方法将把单个电极颗粒的行为与传统电极中使用的复杂结构的影响隔离开来，并在原子尺度上揭示生产过程和竞争过程之间的平衡。该项目将量化基于镁的高能电池开发中的关键瓶颈，以解锁下一代充电设备。该项目的活动以教育和培训为中心，为伊利诺伊大学芝加哥分校(UIC)的不同学生群体提供机会，让他们有机会在尖端电化学、材料科学和表征研究方面进行实践研究和学习经验。通过对本科生和研究生进行最先进的原位扫描电子显微镜和电化学的培训，将研究和教育整合在一起，这是该项目的一个重要特征。该研究项目试图通过结合阴极合成、电化学和最先进的电子显微镜来识别和克服过渡金属氧化物阴极中有效嵌入镁离子的根本障碍。目前已有几种氧化物被证明对镁插层具有活性，但该过程需要高温，并伴随着不可接受的高滞后，这对实际应用来说是一个致命的缺陷。本项目的重点是将镁钒氧化物作为一个模型系统，通过在单粒子阴极上进行测量，揭示材料的内在行为，而不是通过复杂的电极体系结构的电池设计和传输来解开有效嵌入镁离子的根本障碍。新型的原位保持器、薄膜模型系统阴极和扫描电子显微镜提供了单个粒子在电化学循环过程中整体和界面转变的原子尺度描述，将可逆插层引起的变化与不可逆竞争反应分开。对多种温度下的反应性的评估将为结构转变的动力学限制提供独特的见解，为镁基阴极在室温或接近室温时走向电池绘制出一条道路。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Li-ion batteries have seen a steady growth in achievable energy storage capacity and durability over the last several years, rendering them the dominant market player. However, accelerating the transition to a society based on renewable energy still requires new alternative battery chemistries. One possible solution is to replace lithium ions as the primary carriers of electronic charges by multivalent carriers like magnesium. The theoretical gains with the use of magnesium are hampered by the inefficient transport of magnesium within the battery at relevant temperatures of operation, especially in the solid oxide cathodes needed for transformational gains in energy density. In this project, novel approaches of electron microscopy are combined to examine the intrinsic reactivity of model transition metal oxides as cathodes in Mg-ion batteries. These approaches will isolate the behavior of individual electrode particles from the effect of the complex architectures used in conventional electrodes and reveal the balance between productive and competing processes at the atomic scale. This project will quantify critical bottlenecks in the development of high-energy batteries based on magnesium to unlock the next generation of rechargeable devices. The project’s activities center around education and training providing the diverse student body at University of Illinois - Chicago (UIC), a Research-1 Hispanic-serving institution with opportunities for hands-on research and learning experiences in cutting-edge electrochemistry, materials science, and characterization research. The integration of research and education through the training of undergraduate and graduate students in state-of-the-art in-situ scanning transmission electron microscopy and electrochemistry is an integral feature of this project.This research project seeks to identify and overcome the fundamental barriers of efficient Mg-ion intercalation in transition metal oxide cathodes using a combination of cathode synthesis, electrochemistry, and state-of-the-art electron microscopy. Several oxides have now been shown to be active toward Mg intercalation, yet the process demands high temperature and is accompanied by an unacceptably high hysteresis, a fatal flaw for practical application. This project focuses on MgV2O4 as a model system to unravel the fundamental barriers to efficient Mg2+ intercalation by conducting measurements on single particle cathodes, revealing the intrinsic behavior of the material, rather than the convolution of cell design and transport across a complex electrode architecture. Novel in-situ holders, thin-film model system cathodes and scanning transmission electron microscopy provide an atomic-scale description of bulk and interfacial transformations of single particles during electrochemical cycling, separating changes due to reversible intercalation from irreversible competing reactions. The evaluation of reactivity at multiple temperatures will provide unique insight into the kinetic limitations of the structural transitions, charting a path for Mg-based cathodes towards a battery at, or near, room temperature.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.