A research team from the Technical University of Munich (TUM) has discovered that dangerous dendrites — tiny, needle-like lithium structures that can cause short circuits — may form not only on a battery’s electrodes but also within the solid electrolyte itself. The finding challenges a central assumption in battery science and has significant implications for the development of safer solid-state batteries.
Dendrites are among the most serious safety challenges in battery technology. These metallic formations can grow uncontrollably within a cell, potentially piercing separators and triggering internal short circuits or fires. Until now, researchers widely believed that solid electrolytes, such as those used in lithium metal solid-state batteries, could suppress dendrite formation by providing a stable barrier between electrodes.
However, nanofocus wide-angle X-ray scattering experiments conducted by the TUM team at the German Electron Synchrotron (DESY) in Hamburg revealed that dendrites can also develop in the middle of solid polymer electrolytes — materials previously considered resistant to such growth. “This is a material that is actually supposed to protect against dendrites,” said physicist Fabian Apfelbeck, lead author of the study published in Nature Communications.
The discovery overturns a long-held belief about how and where dendrites form. “Until now, it was assumed that dendrite growth occurs only at the interface between electrode and electrolyte. The fact that it also appears far away from that interface surprised us,” said Prof. Peter Müller-Buschbaum, Chair of Functional Materials at TUM. “This new knowledge helps us develop — and further improve — materials in which such internal crystallization processes do not occur in the first place, enabling more efficient, safer, and longer-lasting energy storage.”
The study underscores that solid-state batteries, despite their promise, are not automatically immune to short-circuit risks. Researchers say the industry must now reconsider how solid electrolytes are designed and tested to create truly stable and safe energy storage solutions for future electric vehicles and portable electronics.
