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Flameproofing lithium-ion ies containing this electrolyte continue to
batteries with salt function at high temperatures without
starting a fire.
STANFORD, Calif. — Rechargeable
lithium-ion batteries power phones, Their secret? More salt.
laptops, other personal electronics
and electric cars, and are even used to Potential firestarter
store energy generated by solar pan- Conventional lithium-ion battery electro-
els. But if the temperature of these lytes are made of a lithium salt dissolved
batteries rises too high, they stop in a liquid organic solvent, such as ether
working and can catch fire. or carbonate. While this solvent improves
battery performance by helping to move
Flammable electrolyte lithium ions around, it’s also a potential
That’s in part because the electrolyte in- firestarter.
side of them, which ferries lithium ions
between the two electrodes as the battery Batteries generate heat as they operate.
charges and discharges, is flammable. And if there are punctures or defects in a
battery, it will heat up rapidly. At tempera-
tures above 140 degrees F, the small mol-
ecules of solvent in the electrolyte start to
evaporate, transforming from liquid to gas
and inflating a battery like a balloon — un-
til the gas catches fire and the whole thing
goes up in flames.
Over the past 30 years researchers have
developed non-flammable electrolytes,
such as polymer electrolytes, which use a
polymer matrix instead of the classic salt-
Rachel Huang is the first author of a paper reporting on a non- solvent solution to move ions around.
flammable electrolyte for lithium-ion batteries. (Stanford)
Making it safe Safer alternatives
“One of the biggest challenges in the bat- However, these safer alternatives don’t
tery industry is this safety issue, so there’s move ions as efficiently as liquid solvents
a lot of effort going into trying to make a do, so their performance has not mea-
battery electrolyte that is safe,” said Ra- sured up to that of conventional electro-
chel Z Huang, a graduate student at Stan- lytes.
ford University and first author of a report
published in Matter. The team wanted to produce a polymer-
based electrolyte that could offer both
Huang developed a non-flammable elec- safety and performance. And Huang had
trolyte for lithium-ion batteries with 19 an idea.
other researchers at the Department of
Energy’s SLAC National Accelerator Labo- She decided to add as much as she could
ratory and Stanford University. of a lithium salt called LiFSI to a polymer-
based electrolyte designed and synthe
Their work demonstrated that batter- next page
