Groundbreaking research from engineers at Brown University has unveiled a new strategy to address a critical challenge in the advancement of solid-state lithium batteries. These batteries are anticipated to revolutionize energy storage solutions, particularly for electric vehicles, by offering enhanced safety, faster charging, and greater range compared to conventional liquid electrolyte batteries.
The primary obstacle hindering the commercialization of solid-state batteries is the formation of lithium dendrites. These dendrites are needle-like structures that can develop within the battery’s electrolyte during charging at high currents. They pose a significant risk by creating unwanted electrical connections between the anode and cathode, ultimately leading to battery failure.
In a study published in the journal Joule in March 2023, the Brown researchers demonstrated a surprisingly straightforward method to mitigate dendrite growth. By applying mechanical stress through temperature gradients across the electrolyte, they achieved substantial improvements in dendrite-free charging performance.
Zikang Yu, a graduate student in Brown’s School of Engineering and the lead author of the study, emphasized the significance of their findings, stating, “Dendrites are one of the biggest challenges plaguing next-generation solid-state batteries. 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.”
In their experiments, the researchers employed lithium metal electrodes separated by the solid electrolyte LLZTO (Li6.4La3Zr1.5Ta0.5O12), a material noted for its high ionic conductivity yet susceptible to dendrite formation at elevated charging rates. They utilized a ceramic heating ring to heat one side of the electrolyte while cooling the opposite 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.”
The application of this thermal compression effectively reduced dendrite penetration, even in materials traditionally prone to such growth. Testing revealed that the critical current density of the LLZTO electrolyte—its maximum charging current without failure—tripled under the applied compression.
Yu expressed optimism about the practical implications of this research, suggesting that the findings could lead to viable solutions for the dendrite issue in solid-state batteries. “We think there’s potential to implement this into a practical cell,” he stated. “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.”
The promising results have motivated the research team to continue exploring this innovative approach. Chenjie Gan, an engineering graduate student and coauthor of the study, highlighted the importance of these findings in validating their theoretical framework. “This experiment was a validation of our theoretical work,” said Gan. “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 study received financial support from 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). This research not only represents a significant step forward in battery technology but also offers hope for the future of sustainable energy solutions.
