Tech Briefs Magazine - October 2021 - 36

Power & Energy
Safer, Less Expensive, Fast-Charging Aqueous Battery
A new anode for aqueous batteries uses seawater as an electrolyte.
University of Houston, Texas
ithium-ion batteries are critical for
modern life, powering laptops, cellphones,
and other devices; however,
there is a safety risk - the batteries can
catch fire. Zinc-based aqueous batteries
avoid the fire hazard by using a waterbased
electrolyte instead of the conventional
chemical solvent. But uncontrolled
dendrite growth limits their ability to provide
the high performance and long life
needed for practical applications.
Researchers have created a new 3D
zinc-manganese nano-alloy anode that
results in a stable, high-performance, dendrite-free
aqueous battery using seawater
as the electrolyte. The discovery offers
L
promise for energy storage and other
applications including electric vehicles.
The team also developed an in situ optical
visualization technique, allowing them
to directly observe the reaction dynamics
on the anode in real time. The platform
provides direct evidence and visualization
of the reaction kinetics. Testing determined
that the novel 3D zinc-manganese
nano-alloy anode re mained stable without
degrading throughout 1,000 hours of
charge/discharge cycling under high current
density.
The anode is the electrode that releases
current from a battery, while electrolytes
are the medium through which
the ionic charge flows between the cathode
and anode. Using seawater as the
electrolyte rather than highly purified
water offers another avenue for lowering
battery cost.
Traditional anode materials used in
aqueous batteries have been prone to
dendrites - tiny growths that can cause
the battery to lose power. The new strategy
efficiently minimizes and suppresses
dendrite formation in aqueous systems by
controlling surface reaction thermodynamics
with a zinc alloy and reaction
kinetics by a three-dimensional structure.
For more information, contact Jeannie
Kever at jekever@uh.edu.
Using Solar Technology to Power Smart Devices Indoors
An already ubiquitous material in outdoor photovoltaic modules could be repurposed for
indoor devices with low-capacity batteries.
National Institute of Standards and Technology, Gaithersburg, Maryland
S
olar or photovoltaic (PV) cells fixed to
roofs convert sunlight into electricity.
Bringing that technology indoors could
further boost the energy efficiency of
buildings and energize swaths of wireless
smart technologies such as smoke alarms,
cameras, and temperature sensors.
A straightforward approach was developed
for capturing light indoors. Re -
searchers tested the indoor charging ability
of small modular PV devices made of
different materials and then hooked up
the lowest-efficiency module - composed
of silicon - to a wireless temperature
sensor. The results demonstrate that
the silicon module, absorbing only light
from an LED, supplied more power than
the sensor consumed in operation. This
suggests that the device could run continuously
while lights remain on, which
would do away with the need for someone
to manually exchange or recharge
the battery.
Most buildings are lit by a mix of both
the Sun and artificial light sources during
the day. At dusk, the latter could continue
to supply energy to devices. However, light
36
Cov
Researchers tested miniature solar modules made of three different materials under artificial light.
The modules were made of (left to right) silicon, gallium arsenide, and gallium indium phosphide.
(Credit: NIST)
from common indoor sources, such as
LEDs, spans a narrower spectrum of light
than the wider bands emitted by the Sun
and some solar cell materials are better at
capturing these wavelengths than others.
To find out exactly how a few different
materials would stack up, the team tested
PV mini-modules made of gallium indium
phosphide (GaInP), gallium arsenide
(GaAs) - two materials geared toward
white LED light - and silicon, a less effiwww.techbriefs.com
ToC
cient
but more affordable and commonplace
material. The researchers placed the
centimeters-wide modules underneath a
white LED housed inside an opaque black
box to block out external light sources.
The LED produced light at a fixed intensity
of 1000 lux, comparable to light levels in
a well-lit room, for the duration of the
experiments. For the silicon and GaAs PV
modules, soaking in indoor light proved
less efficient than sunshine but the GaInP
Tech Briefs, October 2021

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Tech Briefs Magazine - October 2021

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