Overworking or overcharging a
lithium-ion battery can cause deformation in its spiral-shaped electrode. Which causes it to explode if care is not taking.
From the fiery Note 7 debacles to exploding hover-boards, lithium-ion batteries
aren't doing so hot lately. A new study helps to explain
how these popular power sources can turn into safety hazards.
In the paper, published in the Journal
of the Electrochemical Society, scientists at the Canadian Light Source
(CLS) synchrotron looked inside an overworked battery. In this case, they
drained a battery until its voltage was below a critical level.
Toby Bond, Canadian Light Source
Overcharging or overworking deforms
the insides of a battery. (A) shows the inside of a battery before it was
misused. (B) shows how misuse causes the original design defects to become even
more warped. (C) highlights the areas where warping got worse.
When we overheat or overcharge
lithium ion batteries, the materials inside start to break down and produce
bubbles of oxygen, carbon dioxide, and other gases. Pressure builds up, and the
hot battery swells from a rectangle into a pillow shape. Sometimes the phone
involved will operate afterwards. Other times it will die
To see what's happening inside the
battery when it swells, the CLS team used an x-ray technique called computed
tomography.
Inside the battery is an electrode
that spirals out from a central point like a jellyroll. The x-ray scan revealed
that the bubbles produced during overheating warped and dented this electrode.
Intriguingly, the study authors
found that the worst deformation from the gas buildup occurred in areas that
had slight defects before the battery was ever over-drained. The authors note
that doing more studies like this, on a larger variety of batteries, would
improve understanding of how these batteries respond to gas evolution, which
could lead to better designs.
As New Scientist notes, it's not clear whether the Samsung Note 7
catastrophes included pillowing or this type of deformation.
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