Researchers at MIT and the Technical University of Munich have identified why solid-state batteries are prone to failure due to lithium metal dendrite formation at grain boundaries within solid electrolytes. Their findings, published in Nature Nanotechnology, reveal that local electrical imbalances at these boundaries alter how the electrolyte conducts charges, promoting the growth of microscopic lithium spikes that degrade battery performance.
Solid electrolytes consist of densely packed ceramic crystals, or grains, each separated by grain boundaries. While grain boundaries have long been suspected of contributing to dendrite formation, the underlying mechanisms remained unclear. The research team developed a theoretical model supported by electron microscopy, machine learning simulations, and electrochemical impedance spectroscopy to probe the electrical and chemical behavior at these interfaces.
They discovered that grain boundary cores carry localized charges, creating electric fields that impede lithium-ion mobility and encourage electron accumulation. These electrons can reduce lithium ions to metallic lithium within the boundary region, seeding dendrite growth. By adjusting the manufacturing process of a common solid electrolyte material, lithium lanthanum zirconate (LLZO), the team minimized boundary charge imbalances, improving ionic transport rates and reducing electron leakage.
The modified processing conditions yielded an LLZO electrolyte with a critical current density more than three times higher than standard samples. This improvement could enable faster charging rates, extended cycle life, and enhanced safety by delaying short circuits and reducing the risk of thermal runaway.
“Grain boundaries are like defects that disrupt charge carriers,” said senior author Harry Tuller of MIT’s Department of Materials Science and Engineering. “By engineering these interfaces, we’ve demonstrated significant performance gains.”
Former MIT professor Jennifer Rupp, now at the Technical University of Munich, added, “Understanding space charge effects at grain boundaries opens new pathways for designing solid-state batteries with longer lifespans and higher charging capabilities.”
Supported by the National Science Foundation and the U.S. Department of Homeland Security, this work provides a roadmap for engineering next-generation solid-state electrolytes to advance faster, safer, and more durable batteries.
Source: MIT News
