Tech Briefs Magazine - November 2023 - 33

Power & Energy
Carbon Fiber Sleeve Tempers Battery Thermal Runaway
The sleeeve prevents fire hazard in small cylindrical lithium-ion battery cells via
propagation-resistant technology.
Johnson Space Center, Houston, TX
I
nnovators at NASA Johnson Space Center
have developed a carbon fiber reinforced
polymer (CFRP) sleeve, that,
when fitted over a cylindrical Li-ion battery
cell, can prevent cell-to-cell propagation
by containing a thermal runaway
(TR) event to the originating cell.
TR is caused by a battery cell short-circuiting
and its inability to contain the
resulting increase in pressure and temperature,
which may lead to a sidewall
rupture (SWR). Space flight and other
industrial batteries frequently utilize
multiple cells, such as the 18650, that are
assembled into modules or battery packs
and provide power to a variety of applications.
A TR event can propagate to all
the cells in a battery pack, escalating into
a fire that can be catastrophic.
Previous battery designs have addressed
SWR propagation by using aluminum
or steel interstitial materials to
prevent SWRs from directly impacting
neighboring cells, but these materials
were underperforming. During testing
of 18650 battery cells, it was discovered
that cells over 2.6Ah in capacity can have
an undesirable failure mode in which
the cell wall will rupture or breach
during a TR event sending heat and
eject into an undesirable direction.
TR is typically triggered when heat
produced by the battery cells exothermic
reaction leads to increased and escalating
internal cell temperature, pressure,
and boiling of the electrolytes.
When internal cell pressure exceeds the
cells safety relief mechanism, rupture or
bursting can occur, initiating a cell-tocell
propagation that in turn results in a
battery pack fire.
By adding a CFRP sleeve to cylindrical
battery cells, SWR can be prevented from
occurring or propagating. In initial testing,
there were no SWRs of a battery cell
using a CFRP sleeve. This result is believed
to be due in part to a unique characteristic
of CFRP sleeves compared to other materials.
Carbon fiber material has a negative
coefficient of expansion and accordingly
shrinks when heated, while steel and aluTech
Briefs, November 2023
By adding a CFRP sleeve to cylindrical battery cells, SWR can be prevented from occurring or propagating.
(Image: NASA)
An engineer holds a spent test fixture attached to an 18650 Li-ion battery cell with an external
carbon fiber reinforced polymer sleeve. Notice the sleeve intact, even after a thermal runaway event
was induced in the battery cell. (Image: NASA)
minum expand. The shrinking of the
CFRP sleeve when heated compresses the
cell located within it, significantly aiding in
the prevention of SWR.
Use of CFRP sleeves for Li-ion cells
provides multiple advantages over previous
containment designs: increased hazard
safety, lower mass, reduced cost, lack
of conductivity, and manufacture with
readily available materials. This technology
can be implemented into other
www.techbriefs.com
multiphysics battery safety models to
guide the design of the next generation
of battery cells and battery packs.
NASA is actively seeking licensees to
commercialize this technology. Please
contact NASA's Licensing Concierge at
Agency-Patent-Licensing@mail.nasa.gov
or call at 202-358-7432 to initiate licensing
discussions. For more information, visit
https://technology.nasa.gov/patent/
MSC-TOPS-119.
33

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Tech Briefs Magazine - November 2023

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