A coating so thin that it is around 100,000 times thinner than a human hair could help solve one of the biggest challenges facing next-generation batteries.
Researchers at the U.S. Department of Energy’s Argonne National Laboratory have identified magnesium oxide as a promising protective coating for solid-state batteries, offering a potential path toward batteries that store more energy, last longer and are safer than today’s lithium-ion batteries.
Their findings were published in Advanced Science.
Solid-state batteries have attracted worldwide attention because they replace the liquid electrolyte used in conventional lithium-ion batteries with a solid material.
This design could improve safety by reducing the risk of leaks and fires while also allowing batteries to store more energy.
However, many of the most promising solid electrolytes, especially those made from sulfide materials, have a major weakness. They are chemically unstable and can react with other battery components, particularly where they come into contact with lithium metal.
These unwanted reactions increase resistance inside the battery, reduce efficiency and shorten its lifespan.
To address this problem, the research team focused on a sulfide solid electrolyte known as lithium phosphorus sulfur chloride, or LPSCl.
They searched for an extremely thin protective coating that could shield the material without interfering with the movement of lithium ions, which are essential for charging and discharging the battery.
Instead of relying only on laboratory experiments, the scientists first used advanced computer modeling to evaluate many different oxide coatings.
Their calculations predicted how each material would behave at several critical points inside the battery, including where the coating meets the electrolyte, the lithium metal and the battery’s cathode.
One surprising finding was that the best coating was not necessarily the one that reacted the least. Instead, what mattered most was the type of compounds created if a reaction occurred.
The most successful coatings produced reaction products that still allowed lithium ions to move freely while blocking the flow of electrons, helping the battery continue operating efficiently.
Among all the materials tested, magnesium oxide stood out. The researchers then applied an ultra-thin layer of magnesium oxide onto LPSCl using atomic layer deposition, a manufacturing technique capable of creating highly uniform coatings only about one nanometer thick.
Tests showed that the coating made the electrolyte more stable when it touched lithium metal, reduced resistance at the interface and improved the battery’s overall performance.
The team also confirmed that the coating evenly covered the electrolyte particles using advanced imaging techniques.
By comparison, another material, zirconium oxide, was chemically more stable on its own but formed less useful reaction products and delivered poorer battery performance. Zinc oxide also showed promise because the compounds it formed still allowed efficient lithium-ion movement despite being more chemically reactive.
Beyond identifying magnesium oxide as a strong candidate, the researchers believe they have developed a faster and more reliable way to discover future battery coatings. Instead of testing countless materials through time-consuming experiments, scientists can now use computer models to predict which reaction products are most likely to improve battery performance before moving to laboratory testing.
The new approach could speed the development of advanced solid-state batteries and help researchers explore many other coating materials.
If successful, these ultra-thin protective layers could play an important role in bringing safer, longer-lasting and higher-capacity batteries closer to everyday use in electric vehicles, portable electronics and renewable energy storage systems.
