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

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.