Why solid-state batteries keep short-circuiting

Key Points:

• MIT engineers have discovered that dendrite growth in solid-state lithium metal batteries is driven more by chemical reactions weakening the electrolyte than by mechanical stress, overturning decades of assumptions.
• Using a novel birefringence microscopy technique, the team directly measured stress around dendrites and found that cracks formed at stress levels as low as 25% of what mechanical stress alone would predict.
• Chemical reactions caused by high electrical currents cause electrochemical corrosion, making the electrolyte brittle and more susceptible to dendrite penetration, which explains why stronger electrolytes alone have not solved the problem.
• The findings highlight the need to develop more chemically stable solid electrolytes that can resist degradation in contact with lithium metal, advancing the potential for safer, higher-energy-density solid-state batteries.
• The researchers' approach to directly observing stress and chemical changes could also inform improvements in other electrochemical devices such as fuel cells and electrolyzers.