TUM Researchers Discover Dendrite Growth Inside Polymer Electrolytes, Redefining Safety Challenges for Solid-State Batteries

TUM researcher Fabian Apfelbeck is working with a measuring device that can be used to examine the charging and discharging cycles of button cells.

(IN BRIEF) Researchers at the Technical University of Munich (TUM) have discovered that lithium dendrites — microscopic metal structures that can cause short circuits and fires — can also form within polymer-based electrolytes, not just at the electrode interface as previously believed. Using nanofocus X-ray scattering at DESY, the team visualized these structures developing inside the electrolyte during battery operation. The findings, published in Nature Communications, challenge a central assumption in battery research and could significantly impact the design of safer, more durable solid-state batteries. Led by Prof. Peter Müller-Buschbaum and PhD researcher Fabian Apfelbeck, the study provides new insights into how to prevent internal crystallization and improve battery reliability.

(PRESS RELEASE) MUNICH, 5-Nov-2025 — /EuropaWire/ — A research team from the Technical University of Munich (TUM) has uncovered a surprising and potentially game-changing phenomenon in lithium battery research: dendrites — tiny, needle-like metal structures responsible for short circuits and battery fires — can also grow inside polymer-based electrolytes, not just at the electrodes as previously believed. The discovery, published in Nature Communications, has major implications for the development and stability of next-generation solid-state batteries.

Dendrites, formed from lithium metal, are among the most serious threats to the safety and lifespan of batteries. When they grow unchecked, they can penetrate the electrolyte layer, causing short circuits that may lead to overheating or even explosions. While solid electrolytes — especially polymer-based variants — have been seen as a safer alternative to liquid ones due to their stability and non-flammability, the TUM study challenges this long-held assumption.

“Electrolytes are responsible for transporting lithium ions between the electrodes and enabling the flow of current,” explained Fabian Apfelbeck, a doctoral researcher at TUM’s Chair of Functional Materials under Prof. Peter Müller-Buschbaum, and first author of the study. “Our measurements show that dendrite growth can also occur directly inside the polymer electrolyte — right in the material that is actually supposed to protect against dendrites.”

Using nanofocus wide-angle X-ray scattering experiments at the German Electron Synchrotron (DESY) in Hamburg, the team was able to observe, for the first time, how dendrites evolve inside polymer electrolytes under realistic operating conditions. By directing an ultra-precise 350-nanometer-wide X-ray beam into a miniature working cell, they visualized the internal crystallization processes in unprecedented detail.

Prof. Peter Müller-Buschbaum emphasized the importance of this finding: “Until now, we believed dendrite growth only occurred at the interface between electrode and electrolyte. The fact that it also appears deep within the electrolyte itself surprised us. This insight opens up new avenues for developing materials that can completely suppress such internal crystallization — paving the way for more reliable, efficient, and longer-lasting energy storage systems.”

This discovery marks a significant advancement in understanding the internal dynamics of lithium-metal batteries. It also provides crucial guidance for scientists and engineers striving to design safer solid-state batteries, capable of powering the future of electric mobility and portable electronics with higher energy density and improved safety.

Publications

F. A. C. Apfelbeck, G. E. Wittmann, M. P. Le Dû, L. Cheng, Y. Liang, Y. Yan, A. Davydok, C. Krywka, P. Müller-Buschbaum: Local crystallization inside the polymer electrolyte for lithium metal batteries observed by operando nanofocus WAXS. Nature Communications (2025). DOI: 10.1038/s41467-025-64736-w

Further information and links

• The research was conducted within the Excellence Cluster e-conversion, which explores the fundamental principles of energy conversion and storage at TUM. It was supported by the German Research Foundation (DFG), the Bavarian Research Network Solar Technologies Go Hybrid (SolTech), and the Helmholtz-Zentrum Hereon.
• News about energy research at TUM

Technical University of Munich

Corporate Communications Center

• Caroline Zörlein und Ulrich Meyer
• presse@tum.de
• Teamwebsite

Contacts to this article:

Prof. Dr. Peter Müller-Buschbaum
Technical University of Munich
TUM School of Natural Sciences
Chair of Functional Materials
Excellence cluster e-conversion
muellerb@ph.tum.de

SOURCE: Technical University of Munich