Collaborative Research: Fundamental Study of Niobium Tungsten Oxide Anodes for High-Performance Aqueous Batteries

现代人类社会需要高效、经济、安全的储能手段。如今，可充电锂离子电池主导着从便携式电子产品到快速扩展的电动汽车和电力（电网）存储应用的能源存储领域。然而，目前的锂离子电池存在安全性和成本问题，主要是因为电解质中使用了易燃、湿敏感和昂贵的有机溶剂。该项目旨在用水取代有机溶剂电解质，同时不影响电池性能（即体积和重量的能量和功率密度）。为了实现这一目标，研究小组建议探索新型的复合氧化物（铌钨氧化物）材料，这种材料将专门为水电池化学设计，从而为下一代水电池在体积能量和功率密度方面取得突破性进展。这项工作将有助于开发低成本、高性能和安全的水电池，这对大规模储能至关重要。该项目将解决许多基础科学和工程问题，以便成功开发具有铌钨氧化物阳极的水性锂离子电池。这些包括：(1)对氧化铌钨阳极在含水（盐包水）电解质中的化学稳定性进行基准测试，并确定是否需要保护涂层来提高稳定性；(2)深入了解氧化铌钨阳极中水电解质的锂化和衰减机理；(3)研究电池运行过程中形成的界面化学和固体电解质界面；(4)氧化铌钨化合物的组成工程（即合金化和掺杂），以提高其重量和速率性能。在这个项目中，上述每项任务都将使用一个耦合的实验和计算方法来解决，以便对基础科学有一个深入和深入的基础理解。通过优化铌钨氧化物成分和增加水电池的工作电压窗口，从而大幅提高体积和重量能量密度，将评估成功与否。成功与否还取决于该团队是否有能力提高铌钨氧化物在水环境中的高倍率性能，从而显著提高快速充电能力。最后，铌钨氧化物电极将被优化和设计，以稳定和安全的方式在数千个充放电步骤中以高库仑效率循环。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Modern human society requires efficient, affordable and safe means for energy storage. Today, rechargeable lithium–ion batteries dominate the energy storage landscape from portable electronics to the rapidly expanding electric vehicles and electricity (grid) storage applications. However, current lithium-ion batteries suffer from safety and cost issues, primarily because of flammable, moisture-sensitive and expensive organic solvents used in the electrolytes. This project is aimed at replacing the organic solvent electrolyte with water, in a manner that does not compromise on battery performance (i.e., volumetric and gravimetric energy and power density). To accomplish this, the research team proposes to explore new classes of complex oxide (niobium tungsten oxide) materials that will be designed specifically for aqueous battery chemistries, enabling breakthrough improvements in volumetric energy and power density for the next generation of aqueous batteries. This work will contribute to low-cost, high-performance and safe aqueous batteries that are critical for large-scale energy storage. A number of fundamental science and engineering issues will be addressed in this project in order to enable the successful development of aqueous lithium-ion batteries with niobium tungsten oxide anodes. These include: (1) Benchmarking the chemical stability of niobium tungsten oxide anodes in aqueous (water-in-salt) electrolytes and establishing whether a protective coating is needed to improve stability; (2) Developing an in-depth understanding of aqueous electrolyte lithiation and delithation mechanism(s) in niobium tungsten oxide anodes; (3) Studying the interfacial chemistry and solid electrolyte interface that develops during battery operation; and (4) Compositional engineering (i.e., alloying and doping) of niobium tungsten oxide compounds to improve their gravimetric and rate performance. In this project, each of the above tasks will be addressed using a coupled experimental and computational approach, so that a deep and in-depth fundamental understanding of the underlying science can be achieved. Success will be assessed by an ability to optimize the niobium tungsten oxide composition and increase the operating voltage window of the aqueous battery, leading to a substantial increase in volumetric and gravimetric energy density. Success will also be determined by the team’s ability to enhance the high-rate performance of niobium tungsten oxides in an aqueous setting, leading to significant improvement in fast charging capability. Finally, the niobium tungsten oxide electrodes will be optimized and engineered to cycle in a stable and safe manner over thousands of charge-discharge steps with high coulombic efficiency.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.