Key Takeaways:
UH engineer discovers that lithium dendrites, a flaw in batteries, are unexpectedly strong and brittle allowing them to act like rigid needles inside batteries
Their stiffness—enhanced by a protective coating—enables them to pierce separators, causing short circuits and safety risks
First-ever real-time observations explain brittle nature
Findings may help improve safety and reliability of high-energy storage systems
HOUSTON, April 8 -- A University of Houston engineer has found that lithium dendrites—hazardous growths inside lithium-ion batteries that power everything from smartphones to electric vehicles—are unexpectedly strong and brittle, signaling a need to rethink future battery design.
The growth and penetration of lithium dendrites through electrolytes and separators remain key challenges to realizing high–energy density lithium-metal batteries.
The dendrites are tiny crystal 'needles' that form inside the batteries for a variety of reasons, from fast charging to low temperatures. Though minute, measuring just hundreds of nanometers (more than 100-times smaller than a strand of human hair), lithium dendrites can cause catastrophic damage and safety hazards including short circuits and fires.
"For decades, the scientific community assumed that solid-state electrolytes could easily block dendrites because lithium was thought to be a soft, ductile metal. We have proven they are actually brittle and snap like glass," said Yan Yao, Hugh Roy and Lillie Cranz Cullen Distinguished Professor of electrical and computer engineering. Yao's work is published in Science, in an article co-authored by his colleagues from Rice University, Georgia Institute of Technology and Institute of High-Performance Computing in Singapore. Together, the team reports exactly how these structures behave inside batteries.
The article explains that the stiffness of the dendrites is intrinsic to their nanoscale single-crystal lithium core and further reinforced by a protective surface coating, a combination that enables them to pierce separators.
Yao not only proved the brittle mechanical nature of the dendrites, but he also captured video of the dendrites in action by performing operando SEM imaging allowing them to observe lithium dendrites actually snapping in real time within operating solid-state cells.
"By filming this happening inside a working solid-state battery for the first time—using a specialized air-free chamber we invented here at UH—we've shown that the strategies used to design next-generation batteries have to change," said Yao, who also serves as a Principal Investigator with the Texas Center for Superconductivity at UH.
The custom air-free vessel specifically created by Yao for testing solid-state batteries is already seeing widespread adoption. The technology led to the launch of the startup Solid Design Instruments LLC, which has already sold eight units to national laboratories and major battery companies.
By understanding the true mechanical strength of these dendrites, the researchers suggest that in the future lithium alloy anodes may make dendrites less prone to brittle fracture; a strategy is also currently being explored in various other contexts.
This is the latest in Yao's quest to reimagine solid-state batteries. Previously, he and his team uncovered what caused solid-state batteries to break down and how that process could be slowed. Unlocking that secret was the first step to improving the battery life for everything from cell phones and laptops to electric vehicles.
Adding to that potential, Bo Zhao, an award-winning and internationally recognized engineering professor at the Cullen College of Engineering, discovered a technique to control the flow of heat in electronics , which would ultimately help prolong battery endurance.
Together, these discoveries exemplify how UH is paving the way for alternate energy resources.
This research was supported by the U.S. Department of Energy (DE-EE0008864, DE- SC0018193), the Welch Foundation (C-1716, C-2248, C-2065) and the U.S. National Science Foundation (2239545).
