PROVIDENCE, R.I. [Brown University] — New research by Brown University engineers identifies a simple strategy for combatting a major stumbling block in the development of next-generation solid-state lithium batteries.
Solid-state batteries are considered the next frontier in energy storage, particularly for electric vehicles. Compared to current liquid electrolyte batteries, solid-state batteries have the potential for faster charging, longer range and safer operation due to decreased flammability. But there's been a consistent problem holding back their commercialization: lithium dendrites.
Dendrites are filaments of lithium metal that can grow inside a battery's electrolyte (the part of the battery that separates the anode from the cathode) during charging at high current. When they grow across the electrolyte, dendrites cause circuits between the battery's anode and cathode, which destroy the battery. So while solid electrolytes can, in theory, enable faster charging than liquid electrolytes, the dendrite problem is one of the primary limitations that has to date prevented them from reaching that potential.
But in a new study published in the journal Joule , the Brown researchers demonstrate a surprisingly simple method for combatting dendrite growth. They show that mechanical stress created by temperature differences on either side of an electrolyte can significantly suppress dendrite formation, enabling dramatic improvements in dendrite-free charging performance.
"Dendrites are one of the biggest challenges plaguing next-generation solid-state batteries," said Zikang Yu, a graduate student in Brown's School of Engineering and the paper's lead author. "But we show that temperature-induced mechanical stress effectively suppresses them. We can get a three-fold performance improvement in charging performance of the cell with just a 20-degree temperature gradient."
For the study, the researchers, who are affiliated with Brown's Initiative for Sustainable Energy , tested battery systems using lithium metal electrodes separated by the solid electrolyte LLZTO (Li₆.₄La₃Zr₁.₅Ta₀.₅O₁₂), a material known for its high ionic conductivity but also its vulnerability to dendrite formation at high charging rates. They heated one side of the electrolyte with a ceramic heating ring and cooled the other side with a copper heat sink.
"When you heat something up it expands," explained Brian Sheldon, a professor of engineering and the study's corresponding author. "But if you heat it up more on one side than the other, the expansion is constrained by the cool side, which forces it into compression. That's the whole trick here."
Testing showed that the thermal compression markedly reduced dendrite penetration, even in a material that's prone to them. With compression applied, the LLZTO electrolyte's critical current density — the maximum charging current it can withstand without failing — increased three-fold.
Yu said he's hopeful that the work could point toward a practical solution for the dendrite problem in solid-state batteries.
"We think there's potential to implement this into a practical cell," Yu said. "Whenever a battery is cycled, heat is generated, and there are thermal management systems to deal with that. We think it may be possible to align that thermal architecture in a way that produces the kinds of gradients we generated in this work."
Chenjie Gan, an engineering graduate student and study coauthor who worked on the theoretical side of the research, said these promising results have encouraged the team to continue exploring their approach.
"This experiment was a validation of our theoretical work," Gan said. "We can now think about proposing optimal material properties and loading conditions to fully take advantage of this effect. That's the future direction with this work."
The research was supported by the National Science Foundation (DMR 2124775), the Department of Energy and the Office of Naval Research (N00014-21-1-2815 and N00014-23-1-2688).
