The research was conducted by scientists from Stanford University and the Department of Energy's SLAC National Accelerator Laboratory. The team captured the first-ever atomic-level images of dendrites, which can break through the barriers between different segments of a battery, which causes short circuits or fires. The cryo-EM images show lithium metal dendrites as long, six-sided crystals rather than the pitted, irregular shapes seen in earlier electron microscope imagery.
This technique lets researchers freeze batteries at any point in its charge-discharge cycle, remove various components, and see what's happening on an atom-by-atom basis. They can then make stop-action movies of the activity with the different images they take, which provides previously-unheard of insight into the process going on inside a high-energy battery. The current team was able to see both dendrites and the solid electrolyte interphase (SEI) coating on each one — controlling the SEI stability is important for efficient batteries.
"With cryo-EM, you can look at a material that's fragile and chemically unstable and you can preserve its pristine state – what it looks like in a real battery – and look at it under high resolution," said professor and research leader Yi Cui in a statement. "This includes all kinds of battery materials. The lithium metal we studied here is just one example, but it's an exciting and very challenging one."