Video of lithium air nanobattery bubble formation helps researchers
The video uses an in-situ environmental transmission electron microscope at the Environmental Molecular Sciences Laboratory, part of the US Department of Energy’s Pacific Northwest National Laboratory. Chongmin Wang (above) and his colleagues built a nanobattery inside the microscope’s column that allowed them to watch as the battery charged and discharged inside.
Popping out from the battery’s flat surface is a grey bubble that grows bigger and bigger. Later, the bubble deflates, the top turning inside of itself until only a scrunched-up shell is left behind.
Lithium air batteries have about three times the energy capacity by weight of today’s lithium-ion batteries but has several challenges, such as losing energy as it stores and releases its charge.
“If we fully understand the bubble formation process, we could build better lithium-air batteries that create fewer bubbles,” said Wang. “The result could be more compact and stable batteries that hold onto their charge longer.”
The video data led the team to propose that as the battery discharges, a sphere of lithium superoxide jets out from the battery’s positive electrode and becomes coated with lithium oxide. The sphere’s superoxide interior then goes through a chemical reaction that forms lithium peroxide and oxygen. Oxygen gas is also released and inflates the bubble. When the battery charges, lithium peroxide decomposes, and leaves the former bubble to look like a deflated balloon.
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