Lithium-sulfur (Li-S) batteries, often seen as a promising alternative to lithium-ion (Li-ion) technology, could offer higher energy densities and lower costs while using Earth-abundant materials like sulfur. However, significant hurdles, including short cycle life, material instability, and safety concerns, limit their commercial adoption.

Credit: (Image by Argonne National Laboratory/Guiliang Xu.)
A schematic depiction of the synchrotron X-ray experiment used in this research at the APS to study the Li-S battery cell.
Potential and challenges of Li-S batteries
Li-S batteries differ from Li-ion batteries in how they store and transfer energy. While Li-ion batteries rely on the movement of lithium ions between layered cathodes and anodes, Li-S batteries depend on chemical reactions involving sulfur. Polysulfide compounds are formed during these reactions, and some dissolve in the electrolyte. This “shuttling” effect causes material from the sulfur cathode to migrate to the anode, leading to reduced performance and shorter battery life.
“Numerous strategies have been proposed to mitigate polysulfide shuttling and other challenges,” notes Argonne National Laboratory chemist Guiliang Xu. “One such strategy, using an additive in the electrolyte, has long been thought to be incompatible due to chemical reactivity with the sulfur cathode and other battery parts.”
A new approach
Researchers at the U.S. Department of Energy’s Argonne National Laboratory are investigating the use of a Lewis acid additive in the electrolyte, designed to form a thin film on the electrodes that suppresses the shuttling effect and improves the stability of the cell. “The key is to have a minor reaction to form the film without a continuous reaction that consumes the material and reduces energy density,” Xu explains.
Initial results show reduced polysulfide dissolution and improved reaction homogeneity. X-ray techniques performed at Argonne’s Advanced Photon Source and Brookhaven National Laboratory confirmed that the electrolyte design minimized known issues like polysulfide shuttle and enhanced ion transfer within the battery.
Safety and stability concerns
Even with improved electrolyte designs, other challenges persist. Lithium metal in Li-S batteries reacts easily, raising safety concerns. Researchers are working to develop safer electrolytes to stabilize lithium and reduce flammability, though these efforts remain ongoing.
Outlook and skepticism
While the research marks progress, commercial adoption of Li-S batteries is not guaranteed. The complexities of stabilizing sulfur and lithium components and the broader safety risks suggest that further development is needed before Li-S batteries can compete with established Li-ion systems.
Xu and his team acknowledge the road ahead. “With further optimization and development of sulfur electrodes, we believe Li-S batteries can achieve higher energy density and better overall performance,” Xu says, though their real-world viability remains uncertain.
The study, published in Joule, was supported by the Vehicle Technologies Office of the DOE’s Office of Energy Efficiency and Renewable Energy.