Battery breakthrough gives boost to electric flight and long-range
electric cars

Date:
July 20, 2020
Source:
DOE/Lawrence Berkeley National Laboratory
Summary:
Researchers have developed a new battery material that could enable
long- range electric vehicles that can drive for hundreds of miles
on a single charge, and electric planes called eVTOLs for fast,
environmentally friendly commutes.



FULL STORY ==========================================================================
In the pursuit of a rechargeable battery that can power electric vehicles
(EVs) for hundreds of miles on a single charge, scientists have endeavored
to replace the graphite anodes currently used in EV batteries with
lithium metal anodes.


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But while lithium metal extends an EV's driving range by 30-50%, it
also shortens the battery's useful life due to lithium dendrites, tiny
treelike defects that form on the lithium anode over the course of many
charge and discharge cycles. What's worse, dendrites short-circuit the
cells in the battery if they make contact with the cathode.

For decades, researchers assumed that hard, solid electrolytes, such
as those made from ceramics, would work best to prevent dendrites from
working their way through the cell. But the problem with that approach,
many found, is that it didn't stop dendrites from forming or "nucleating"
in the first place, like tiny cracks in a car windshield that eventually spread.

Now, researchers at the Department of Energy's Lawrence Berkeley
National Laboratory (Berkeley Lab), in collaboration with Carnegie Mellon University, have reported in the journal Nature Materials a new class
of soft, solid electrolytes -- made from both polymers and ceramics --
that suppress dendrites in that early nucleation stage, before they can propagate and cause the battery to fail.

The technology is an example of Berkeley Lab's multidisciplinary
collaborations across its user facilities to develop new ideas to
assemble, characterize, and develop materials and devices for solid
state batteries.

Solid-state energy storage technologies such as solid-state lithium
metal batteries, which use a solid electrode and a solid electrolyte,
can provide high energy density combined with excellent safety, but the technology must overcome diverse materials and processing challenges.



==========================================================================
"Our dendrite-suppressing technology has exciting implications for the
battery industry," said co-author Brett Helms, a staff scientist in
Berkeley Lab's Molecular Foundry. "With it, battery manufacturers can
produce safer lithium metal batteries with both high energy density and a
long cycle life." Helms added that lithium metal batteries manufactured
with the new electrolyte could also be used to power electric aircraft.

A soft approach to dendrite suppression Key to the design of these
new soft, solid-electrolytes was the use of soft polymers of intrinsic microporosity, or PIMs, whose pores were filled with nanosized ceramic particles. Because the electrolyte remains a flexible, soft, solid
material, battery manufacturers will be able to manufacture rolls of
lithium foils with the electrolyte as a laminate between the anode and
the battery separator. These lithium-electrode sub-assemblies, or LESAs,
are attractive drop-in replacements for the conventional graphite anode, allowing battery manufacturers to use their existing assembly lines,
Helms said.

To demonstrate the dendrite-suppressing features of the new PIM composite electrolyte, the Helms team used X-rays at Berkeley Lab's Advanced Light
Source to create 3D images of the interface between lithium metal and
the electrolyte, and to visualize lithium plating and stripping for up
to 16 hours at high current. Continuously smooth growth of lithium was
observed when the new PIM composite electrolyte was present, while in
its absence the interface showed telltale signs of the early stages of dendritic growth.

These and other data confirmed predictions from a new physical model
for electrodeposition of lithium metal, which takes into account both
chemical and mechanical characteristics of the solid electrolytes.

"In 2017, when the conventional wisdom was that you need a hard
electrolyte, we proposed that a new dendrite suppression mechanism
is possible with a soft solid electrolyte," said co-author Venkat
Viswanathan, an associate professor of mechanical engineering and faculty fellow at Scott Institute for Energy Innovation at Carnegie Mellon
University who led the theoretical studies for the work. "It is amazing
to find a material realization of this approach with PIM composites."
An awardee under the Advanced Research Projects Agency-Energy's (ARPA-E)
IONICS program, 24M Technologies, has integrated these materials into
larger format batteries for both EVs and eVTOL (electric vertical takeoff
and landing) aircraft.

"While there are unique power requirements for EVs and eVTOLs, the
PIM composite solid electrolyte technology appears to be versatile and
enabling at high power," said Helms.


========================================================================== Story Source: Materials provided by
DOE/Lawrence_Berkeley_National_Laboratory. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Chengyin Fu, Victor Venturi, Jinsoo Kim, Zeeshan Ahmad, Andrew
W. Ells,
Venkatasubramanian Viswanathan, Brett A. Helms. Universal
chemomechanical design rules for solid-ion conductors to prevent
dendrite formation in lithium metal batteries. Nature Materials,
2020; 19 (7): 758 DOI: 10.1038/s41563-020-0655-2 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200720102044.htm

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