MIT team decodes 'cracks' that cause short circuits in batteries

MIT engineers have discovered that dendrites—microscopic, branch-like structures responsible for short circuits in solid-state batteries—grow faster under low mechanical stress, overturning the long-held belief that mechanical stress primarily drives their formation. Using an advanced stress-mapping technique and birefringence microscopy, the team observed dendrite growth in real time within ceramic electrolytes commonly used in these batteries. Their findings showed that cracks and dendrites form at only about 25% of the previously expected stress threshold. This surprising result indicates that the electrolyte weakens significantly during battery operation, becoming more brittle and vulnerable to failure. The study identifies electrochemical reactions driven by high electrical currents as the key factor weakening the electrolyte, rather than mechanical stress alone. These reactions reduce the structural integrity of the ceramic electrolyte, making it more susceptible to dendrite penetration and short circuits. This insight shifts the focus of solid-state battery research from solely developing mechanically stronger materials to prioritizing chemically stable electrolytes that can endure dynamic operating conditions. The