The ORNL team’s electron microscopy could help researchers address long-standing issues related to battery performance and safety.
Dendrites form when metallic lithium takes root on a battery’s anode and begins growing haphazardly. If the dendrites grow too large, they can puncture the divider between the electrodes and short-circuit the cell, resulting in catastrophic battery failure.
The researchers studied dendrite formation by using a miniature electrochemical cell that mimics the liquid conditions inside a lithium-ion battery. Placing the liquid cell in a scanning transmission electron microscope and applying voltage to the cell allowed the researchers to watch as lithium deposits - which start as a nanometer-size seed - grew into dendritic structures.
“It gives us a nanoscopic view of how dendrites nucleate and grow,” said ORNL’s Raymond Unocic, in situ microscopy team leader. “We can visualize the whole process on a glassy carbon microelectrode and observe where the dendrites prefer to nucleate and also track morphological changes during growth.”
In addition to imaging the structures at high-resolution, the team’s microscopy technique gathered precise measurements of the cell’s electrochemical performance. “This technique allows us to follow subtle nano-sized structural and chemical changes that occur and more importantly, correlate that to the measured performance of a battery,” said Robert Sacci, ORNL postdoctoral researcher and lead author of the Nano Letters study.
The real-time analysis in a liquid environment sets the ORNL team’s approach apart from other characterization methods.