Lithium dendrites propagate through a solid electrolyte like water cracks a rock - it could be prevented with a different design
To the point:
- More powerful batteries: Solid-state batteries come with a higher energy-storage capacit and increased safety compared to the widely used lithium-ion batteries, but they currently often fail to achieve the necessary lifespan.
- Harmful metal trees: During charging, dendrites form at the electrodes and penetrate the solid electrolyte, leading to short circuits over time.
- Pressure from the soft metal: The dendrites penetrate the solid electrolyte because lithium deposits in existing cracks and exerts pressure that creates further cracks. Through these, the metal trees grow until a short circuit occurs.
- Short-circuit protection: A more stable electrolyte material, redirection of dendrites, and protective coatings on the lithium electrode could extend the lifespan of solid-state batteries.
Tortuous path towards a short-circuit: In solid-state batteries, lithium dendrites make their way through the ceramic electrolyte until a short circuit eventually occurs between the two electrodes. The image was taken by a scanning electron microscope under cryogenic conditions.
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They are considered next-generation batteries: solid-state batteries promise higher storage capacity, even greater safety, and, in theory, a longer service life. This could help electric vehicles achieve a significantly greater range than current models.
A comparison of the structures of lithium-ion and solid-state batteries: Solid-state batteries use a solid electrolyte instead of a liquid one. However, their lifespan is compromised by dendrites, which can cause a short circuit between the electrodes.
Unlike today's widely used lithium-ion batteries, which use a liquid electrolyte between two solid electrodes, solid-state batteries employ a solid electrolyte. This design can increase storage capacity, improve safety and, in theory, extend battery lifetime. However, one major challenge still limits their commercial use. During charging, microscopic intrusions known as dendrites, form. These tiny tree-like structures grow from the Lithium metal electrode, propagate through the solid electrolyte and finally cause short circuits inside the battery.
An interdisciplinary team at the Max Planck Institute for Sustainable Materials has now uncovered how dendrites induce fracture, leading to short circuits. They published their results in the journal Nature.
Soft metal in a solid ceramic electrolyte
Dendrite formation in solid-state batteries is a counterintuitive phenomenon. "Although the electrodes and the forming dendrites consist of lithium metal, which is soft like a gummy bear, the dendrites are able to penetrate the ceramic electrolyte and lead to a short circuit," says Yuwei Zhang, head of the group "Chemo-Mechanics of Battery Materials" at the Max Planck Institute for Sustainable Materials. How can soft dendrites fracture the stiff solid ceramic? There are two hypotheses: either pressure is built up inside the dendrites, that grow in existing cracks, and induces mechanical fracture of the solid electrolyte. Or, electrons leak between the tiny crystallites, of which the solid electrolyte consists, promoting the formation of lithium nuclei at these so-called grain boundaries that interconnect later.
Cross-section of a ceramic electrolyte: The orientation of the different crystal grains is shown in different colors. The black crack runs both between different crystal grains (crystallites) and through individual crystallites. The crystallographic orientation is shown in the lower right corner in a triangle with color gradients between the vertices 001 (red), 101 (green), and 111 (blue).
© Zhang, Y. et al.; Nature 652, 912-918 (2026)
To prove either hypothesis, the researchers used an advanced setup of sample preparation and material's characterization techniques, characterized entirely under vacuum and cryogenic temperatures to exclude any influence from oxygen, water or from the electron beam of the microscopes.
The experimental analysis, which the Max Planck team complemented with calculations, showed: The soft lithium metal can propagate through the rigid ceramic electrolyte in a manner similar to water pressing into the cracks of a rock and creating new fractures. The team calculated that the pressure of the lithium in a dendrite, which is enclosed in an existing crack, leads to brittle fracture of the solid electrolyte in the end. The team on the other hand didn't find proof for the hypothesis that lithium nuclei form at the grain boundaries which then grow together. They observed that no lithium was enriched ahead of the dendrite tip under practical battery operation condition.
Possible ways to prevent or delay dendrite-induced cracking
The Max Planck team is now investigating how lithium dendrites penetrate the solid electrolyte at the very beginning of their formation, before they in a sense blast their way through the material. Furthermore the researchers are now exploring, how to prevent the propagation of the dendrites. Possible approaches include increasing the toughness of the solid electrolyte to delay crack formation, introducing microscopic voids that redirect dendrite growth and deflect cracks, or applying protective coatings to the lithium electrodes to suppress dendrite formation.
"Our findings highlight how crucial a fundamental understanding of materials behaviour is for turning promising technologies into practical, real-world applications", says Yuwei Zhang.
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