From Computation to Coating: Argonne Accelerates Search for Solid-state Battery Materials

LEMONT, Ill.--(BUSINESS WIRE)--The success of a promising class of next-generation batteries may hinge on something almost impossibly thin: a coating just a nanometer thick — roughly 100,000 times thinner than a human hair.

In new research, scientists at the U.S. Department of Energy’s (DOE) Argonne National Laboratory combined computation and experiment to find candidate protective coatings for sulfide-based solid electrolytes and uncover what makes those coatings work. The study points to magnesium oxide as a particularly promising new coating and sets up a faster way to find others.

Solid-state batteries could store more energy and improve safety compared with today’s lithium-ion batteries. But some of the most promising solid electrolytes, especially sulfide-based ones, are chemically fragile. They can react at key battery interfaces, especially where the electrolyte touches lithium metal. Those reactions can hurt performance and shorten battery life.

To tackle that problem, the team studied a type of sulfide solid electrolyte called lithium phosphorus sulfur chloride, or LPSCl. They used an approach based on a computational technique called density functional theory to screen a wide range of oxide coatings made by atomic layer deposition (ALD) — a method that deposits ultrathin, uniform layers with near-atomic precision. They predicted how those coatings would behave at three important battery interfaces: where the coating meets the electrolyte, the lithium metal and the cathode materials.

The team found that the best coatings were not always the least reactive. Instead, the most important factor was what compounds formed when the coating reacted at the interface. The best coatings formed reaction products that still let lithium ions move while limiting electron flow.

The researchers then tested several candidate coatings by applying them to LPSCl powder with ALD. Magnesium oxide in particular stood out. It made the electrolyte more stable when in contact with lithium metal, reduced resistance at the interface and improved performance. It also helped block electron flow while still allowing lithium ions to move efficiently.

The team also used scanning transmission electron microscopy and energy dispersive X-ray spectroscopy at the Center for Nanoscale Materials, a DOE Office of Science user facility at Argonne, to confirm the coatings were uniformly distributed on the powder surfaces.

By contrast, zirconium oxide formed less favorable reaction products and performed poorly. Zinc oxide, despite being predicted to be more reactive overall, still yielded beneficial transport behavior because of the reaction products it formed.

In addition to evaluating candidate protective coatings, this work also provides a better way to search a much larger materials design space.