THE TECH
Researchers at Germany’s Fraunhofer Institute for Ma-
terial and Beam Technology IWS have developed a new
battery cell production process that coats electrodes with
a dry film instead of liquid chemicals. This simplified
process saves energy and eliminates toxic solvents. The
Fraunhofer researchers, with colleagues from Samsung,
describe their findings in a new paper, “Overcoming
binder limitations of sheet-type solid-state cathodes
using a solvent-free dry-film approach,” published in
Energy Storage Materials.
Maxwell Technologies, now a subsidiary of Tesla, is
also working on a dry electrode tech that eliminates the
need for toxic solvents. Once Tesla and partner Panason-
ic get Maxwell’s process up and running, it’s expected to
save loads of money, time and factory space.
Reducing the costs of producing battery cells is a high-
ly desirable end in itself, but the Fraunhofer engineers
see the potential to change the global energy storage
market. For years, Asian companies have dominated the
battery cell market. German (and US) automakers cur-
rently get most of their cells from Korean and Japanese
companies. As the proliferation of EVs and stationary
storage applications increases demand for cells, this is
becoming an increasingly intolerable situation. That’s
why, last November, the German government announced
that it would invest a billion euros to support local bat-
tery cell production (as reported by Reuters).
One reason the Asians dominate the cell market is a
cost advantage - the current process for producing cells is
very energy-intensive, and Germany has famously high
electricity prices. A lower-cost production method could
change the equation.
“Our dry transfer coating process aims to noticeably
reduce the process costs in electrode coating,” said paper
co-author Dr. Benjamin Schumm. “Manufacturers can
eliminate toxic and expensive solvents and save energy
costs during drying. Our technology also facilitates the
use of electrode materials that are difficult or even im-
possible to process wet-chemically. For all these reasons,
we think that our technology can help to achieve interna-Fraunhofer’s dry coating process for electrodes could make cell
production in Europe economical
Image courtesy of Fraunhofertionally competitive battery cell production in Germany
and Europe.”
The current wet-chemical process involves mixing the
active battery materials with additives to create a paste,
adding expensive organic solvents. Elaborate precautions
are necessary to protect workers and the environment
from the toxic solvents. Once the paste has been applied
to thin metal foils, dozens of large heating elements are
used to dry the coated films - this drying procedure is
what racks up the high electricity costs.
The new film transfer technology eliminates these
steps. The IWS engineers mix their active material with
binding polymers, then process this dry mixture in a
rolling mill, where shear forces tear molecular chains
out of the binder polymers. These fibrils join with the
electrode particles to form a web that provides the elec-
trode material with stability. The result is a flexible dry
electrode material layer. In the next step, the rolling mill
laminates the 100-micrometer-thick film onto an alumi-
num foil to form the finished electrode.
The Finnish company BroadBit Batteries is working
with Fraunhofer to commercialize the new process. The
firm has commissioned a pilot plant in its Espoo factory,
which will use the dry coating process to produce new
types of sodium-ion batteries.22