Several electrolyte and thin-film coating technologies, developed at Oak Ridge National Laboratory, have been licensed by BTRY, a battery technology company based in Virginia, to make batteries with increased energy density, at lower cost, and with an improved safety profile in crashes.
The enabling technologies, called Safe Impact Resistant Electrolytes, or SAFIRE, are particularly suitable for application in the electric vehicles and aerospace industries.
ORNL’s technology mixes an additive into the conventional electrolyte. The SAFIRE electrolyte is a liquid under normal operating conditions, allowing solvents to wet all the electrode surfaces just like a traditional battery electrolyte.
However, upon impact, as caused by a car crash or some other mechanical impact event, the additive causes the electrolyte to undergo an immediate and massive rheological shift to become a solid. The solid barrier prevents the positive and negative electrodes from coming into contact and short circuiting. This new stability reduces the need for bulky protective shielding.
This characteristic depends on a colloid—a suspension of tiny, solid particles in a liquid. For the battery colloid, ORNL’s Gabriel Veith and his colleagues at ORNL and the University of Rochester used silica suspended in common liquid electrolytes.
On impact, the silica particles clump together and block the flow of fluids and ions, he explained. The researchers used perfectly spherical, 200-nanometer-diameter particles of silica, or essentially a superfine sand.
One of the ORNL advances involves the production process for the batteries. During manufacture of traditional lithium-ion batteries, an electrolyte is squirted into the battery case at the end of the production process, and then the battery is sealed.
“You can’t do that with a shear-thickening electrolyte because the minute you try to inject it, it solidifies”, says Gabriel Veith
The researchers solved this by putting the silica in place before adding the electrolyte.