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Developing Next-Generation, High-Energy Batteries

With the goal of reducing transportation emissions as part of the US government's net-zero climate goal by 2050, efficient and reliable batteries are a must. To this end, a group of researchers led by the McKelvey School of Engineering at Washington University in St. Louis' is actively pursuing the development of an energy storage system with significantly higher energy density than existing technologies.

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Xianglin Li, Associate Professor of Mechanical Engineering and Materials Science, will head a multi-institutional team funded by $1.5 million from the US Department of Energy’s Advanced Research Projects Agency-Energy (ARPA-E) to develop a lithium-air (Li-air) battery with ionic liquids that will provide effective, dependable, and long-lasting performance for high-energy and high-power applications.

The Phase I funding, spanning 18 months, constitutes a segment of the $15 million grant allocated by ARPA-E to 12 projects spread across 11 states. These initiatives are aimed at advancing next-generation, high-energy storage solutions, with the objective of expediting the electrification of the aviation, railroad, and maritime transportation sectors.

Projects funded by the Pioneering Railroad, Oceanic and Plane ELectrification with 1K energy storage systems (PROPEL-1K) program seek to create emission-free energy storage systems using “1K” technologies that can reach or surpass 1,000 Watt-hour per liter (Wh/L) and 1,000 Watt-hour per kilogram (Wh/kg).

The current commercially available lithium-ion batteries have the specific energy of around 200 watt-hour per kilogram, and those would not work because 1,000 watt-hour per kilogram is beyond their thermodynamic limit. We need to increase that specific energy density by four to five times, so this is a very aggressive goal.

Xianglin Li, Associate Professor, Washington University in St. Louis

The agency stated that if successful, PROPEL-1K technology will electrify all North American railroads, vessels operating only in US territorial waters, and regional aircraft carrying up to 100 people over distances of up to 1000 miles.

For the proposed Li-air flow battery, the team will use a unique electrolyte: ionic liquids with high oxygen solubility, low viscosity, ultra-low volatility and high ionic conductivity.

Additionally, the team will tailor catalysts and lithium metal protection membranes to improve battery performance while minimizing power consumption during electrolyte circulation. Initial experimental findings indicate a tenfold capacity boost through the implementation of circulating electrolytes.

Li added, “All of these components must be put together almost perfectly, because that 1,000 watt-hour per kilogram is near the limit of any energy storage technology. That is why we have a large team with complementary experts on different parts of this whole system. My team will lead the overall design of the system and focus on the cathode where the oxygen reaction would occur.

The researchers will employ ionic liquids with high oxygen solubility, low viscosity, ultra-low volatility, and strong ionic conductivity as a novel electrolyte for the proposed Li-air flow battery.

Along with customizing lithium metal protection membranes and catalysts, the team plans to improve battery performance and lower power usage during electrolyte circulation. Using a circulating electrolyte has been proven to boost capacity tenfold in preliminary testing findings.

Commercial batteries use organic electrolytes, but because our Li-air cell is an open system, that electrolyte would evaporate over time. Ionic liquid is a salt that acts like a liquid but does not evaporate and can flow at room temperature,” Li further stated.

The study’s co-principal investigators are Sherry Quinn, an electrochemist at Powerit; Mark Shiflett, a Foundation Distinguished Professor at the University of Kansas; Ivan Vlassiouk, senior research staff at the Oak Ridge National Laboratory; James Saraidaridis, principal research engineer at Raytheon Technologies Research Center, and Peng Bai, associate professor and Vijay Ramani, the Roma B. & Raymond H. Wittcoff Distinguished University Professor, both in the Department of Energy, Environmental & Chemical Engineering at McKelvey Engineering. They will collaborate to create a prototype that can be improved upon and introduced to the public.

The group will also perform an economic study of its Li-air flow battery systems for the railroad, maritime, and aviation industries to emphasize the significance of developing energy storage solutions beyond the state-of-the-art Li-ion battery technology.


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