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TAP TIMES -23- APRIL 2022
Solid-state batteries may
boost performance by 2X
CAMBRIDGE, Mass.— In the endless
quest to pack more energy into bat-
teries without increasing their weight
or volume, one especially promising These discs were used for testing the researchers’ processing
method for solid-electrolyte batteries. On the left, a sample of
technology is the solid-state battery. the solid electrolyte itself, a material known as LLZO. At center,
the same material coated with the cathode material used in their
tests. At right, the LLZO material with a coating of gold, used to
Solid electrolyte layer facilitate measuring its electrical properties.
Credits:Photo: Pjotrs Žguns
In these batteries, the usual liquid elec-
trolyte that carries charges back and forth Even though the amount of carbon dioxide
between the electrodes is replaced with a present is vanishingly small in air, mea-
solid electrolyte layer. sured in parts per million, its effects turn
out to be dramatic and detrimental.
Such batteries could potentially not only
deliver twice as much energy for their size, Sintering in pure oxygen
they also could virtually eliminate the fire Carrying out the sintering step in pure
hazard associated with today’s lithium-ion oxygen creates bonds that match the
batteries. performance of the best coated surfaces,
without that extra cost of the coating, the
But one thing has held back solid-state researchers say.
batteries: Instabilities at the boundary
between the solid electrolyte layer and the The findings are reported in the journal
two electrodes on either side can dramati- Advanced Energy Materials, in a paper by
cally shorten the lifetime of such batteries. MIT doctoral student Younggyu Kim; Prof.
Bilge Yildiz; and Iradikanari Waluyo and
Some studies have used special coatings Adrian Hunt at Brookhaven National Labo-
to improve the bonding between the lay- ratory.
ers, but this adds the expense of extra
coating steps in the fabrication process. “Solid-state batteries have been desirable
for different reasons for a long time,” Yildiz
No need for coatings says.
Now, a team of researchers at MIT and
Brookhaven National Laboratory have Solid-state safer
come up with a way of achieving results “The key motivating points for solid bat-
that equal or surpass the durability of the teries are they are safer and have higher
coated surfaces, but with no need for any energy density,” but they have been held
coatings. back from large scale commercialization
by two factors, she says: the lower con-
The new method simply requires eliminat- ductivity of the solid electrolyte, and the
ing any carbon dioxide present during a interface instability issues.
critical manufacturing step, called sinter-
ing, where the battery materials are heated Large companies such as Toyota are al-
to create bonding between the cathode and ready at work commercializing early ver-
electrolyte layers, which are made of ce- sions of solid-state lithium-ion batteries.
ramic compounds. mit.edu
