“In the past decade, the majority of Li-S field adopted ether electrolytes to avoid the adverse reactions with carbonate,” Kalra said.

But these batteries would not be commercially viable because the ether electrolyte is highly volatile and has components with a boiling point as low as 42 degrees Celsius, meaning any warming of the battery above room temperature could cause a failure or meltdown. Li-S batteries have already demonstrated exceptional performance in experimental settings using an ether electrolyte - rather than carbonate - because ether does not react with polysulfides. Because of this adverse reaction, previous attempts to use a sulfur cathode in a battery with a carbonate electrolyte solution resulted in nearly immediate shut down and a complete failure of the battery after just one cycle. The challenge of introducing sulfur into a lithium battery with commercially friendly carbonate electrolyte has been an irreversible chemical reaction between intermediate sulfur products, called polysulfides and the carbonate electrolyte. Francis Chair professor in the College’s Department of Chemical and Biological Engineering, who led the research. “Sulfur has been highly desirable for use in batteries for a number of years because it is earth-abundant and can be collected in a way that is safe and environmentally friendly, and as we have now demonstrated, it also has the potential to improve the performance of batteries in electric vehicles and mobile devices in a commercially viable way,” said Drexel’s Vibha Kalra, PhD, George B. This development would not only make sulfur batteries commercially viable, but they would have three times the capacity of Li-ion batteries and last more than 4,000 recharges - the equivalent of 10 years of use, which is also a substantial improvement. Their discovery is a new way of producing and stabilizing a rare form of sulfur that functions in carbonate electrolyte - the energy-transport liquid used in commercial Li-ion batteries. A recent breakthrough by researchers in Drexel’s College of Engineering, published in the journal Communications Chemistry , provides a way to sidestep the obstacles that have subdued Li-S batteries in the past, finally pulling the sought-after technology within commercial reach.

This is because of sulfur’s natural abundance and chemical structure that would allow it to store more energy. Well before the EV surge and battery material shortage, developing a commercially viable sulfur battery has been the battery industry’s sustainable, high-performing white whale.

This also focused attention on the primary providers of the raw materials: countries like Congo and China and raised questions about the human and environmental impact of extracting them from the earth. With global sales of EVs more than doubling in 2021, prices of battery materials like lithium, nickel, manganese and cobalt surged and supply chains for these raw materials, most of which are sourced from other countries, became bottlenecked due to the pandemic. In hopes of making batteries that not only perform better than those currently used in EVs, but also are made from readily available materials, a group of Drexel University chemical engineers have found a way to introduce sulfur into lithium-ion batteries - with astounding results. America’s growing demand for electric vehicles (EVs) has shed light on the significant challenge of sustainably sourcing the battery technology necessary for the broad shift to renewable electric and away from fossil fuels.

Battery cathode