A University of Houston engineer has found that lithium dendrites inside batteries are not soft as previously believed but behave like brittle, rigid structures capable of causing serious damage.
These tiny formations, which grow during charging, have long been known to trigger short circuits and fires.
But researchers led by Yan Yao now show that dendrites are mechanically strong and prone to snapping, more like glass than metal.
The finding challenges a decades-old assumption in battery science that lithium metal is ductile and can be easily blocked by solid-state electrolytes.
Instead, the study shows dendrites can act like stiff needles, piercing internal battery components.
The team directly observed this behavior by capturing real-time footage of dendrites forming and breaking inside a working solid-state battery, offering a rare look at how these structures behave under operating conditions.
Assumptions now overturned
“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 Yao.
Dendrites form as tiny crystal structures, often just hundreds of nanometers wide. Despite their size, they can penetrate separators and electrolytes, leading to internal failures.
The study explains that their stiffness comes from a nanoscale single-crystal lithium core, further strengthened by a surface coating that forms during operation.
This combination allows dendrites to maintain structural integrity as they grow, increasing the risk of them breaching protective barriers inside batteries.
The researchers used operando scanning electron microscopy to film dendrites snapping in real time.
This required a specialized air-free chamber developed at the University of Houston, enabling observation inside an active battery without interference.
These findings also highlight how dendrites form and why they remain dangerous. Lithium dendrites can develop for several reasons, including fast charging and low temperatures.
Though only hundreds of nanometers wide, they are more than 100 times smaller than a human hair.
Despite their size, these structures can trigger short circuits and fires, making them one of the most persistent safety risks in high-energy batteries.
Needle-like failure mechanism
“By filming this happening inside a working solid-state battery for the first time… we’ve shown that the strategies used to design next-generation batteries have to change,” Yao said.
The ability to directly visualize dendrite behavior provides new insight into why solid-state batteries, often considered safer alternatives, still face reliability challenges.
The findings suggest that simply relying on solid electrolytes may not be enough to stop dendrite penetration.
Instead, the researchers point to alternative approaches, such as using lithium alloy anodes, which may reduce the likelihood of brittle fracture.
Understanding the mechanical properties of dendrites could also help engineers design materials that better resist penetration.
The study builds on earlier work by the team on how solid-state batteries degrade over time.
Together, these insights could help improve the safety and lifespan of energy storage systems used in electric vehicles, consumer electronics, and grid applications.
The research was published in the journal Science.