Tech Briefs Magazine - February 2022 - BT-21

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Even when bent at 180 degrees, the supercapacitor performed almost the same as when it was flat and after 5,000 cycles, it retained 97.8 percent
of its capacity. (Photo: University College of London)
orders of magnitude higher at over
10,000 Watt per liter.
The researchers made electrodes from
multiple layers of graphene, creating a
dense but porous material capable of
trapping charged ions of different sizes.
They characterized it using a range of
techniques and found it performed best
when the pore sizes matched the diameter
of the ions in the electrolyte. The
optimized material, which forms a thin
film, was used to build a proof-of-concept
device with both high power and
high energy density.
The 6  6-cm supercapacitor was made
from two identical electrodes layered on
either side of a gel-like substance that
acted as a chemical medium for the transfer
of electrical charge. This was used to
power dozens of light-emitting diodes
(LEDs) and was found to be highly robust,
flexible, and stable.
     
     
Technique Extends Next-Generation Lithium Metal
Batteries
The discovery could enable lightweight, low-cost, long-lasting energy storage for electric vehicles, houses,
and more.
Columbia University, New York, NY
A
mong the limitations of electric vehicles
(EVs) is the lack of a longlasting,
high-energy-density battery
that reduces the need to fuel up on longhaul
trips. The same is true for houses
during blackouts and power grid failures-small,
efficient batteries able to
power a home for more than one night
without electricity don't yet exist. A
major issue is that while rechargeable
lithium metal anodes play a key role in
how well this new wave of lithium batteries
functions, during battery operation,
they are highly susceptible to the growth
of dendrites - microstructures that can
lead to dangerous short-circuiting, catching
on fire, and even exploding.
Researchers have found that alkali
metal additives, such as potassium ions,
can prevent lithium microstructure proliferation
during battery use. They used a
combination of microscopy, nuclear magnetic
resonance (similar to an MRI), and
computational modeling to discover that
adding small amounts of potassium salt
to a conventional lithium battery electrolyte
produces unique chemistry at the
Battery & Electrification Technology, February 2022
conventional lithium electrolyte
lithium
plating
lithium
stripping
conventional lithium electrolyte + potassium
lithium
plating
lithium
stripping
Nuclear magnetic resonance imaging and computer simulations were used to better understand
the reactivity and structure of molecules on the surface of lithium metal anodes that
could lead to improved performance. (Photo: Lauren Marbella/Columbia Engineering)
lithium/electrolyte interface. Specifically,
they found that potassium ions mitigate
the formation of undesirable chemical
compounds that deposit on the surface of
lithium metal and prevent lithium-ion
transport during battery charging and discharging,
ultimately limiting microstructural
growth.
The discovery that alkali metal additives
suppress the growth of nonconductive
compounds on the surface of lithium
metal differs from traditional electrolyte
21
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Tech Briefs Magazine - February 2022

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