NEWS & TECHNOLOGY BATTERIES
Fast charging lithium aqueous battery
A By Nick Flaherty team of engineers at Rensselaer Polytechnic Institute in
the US have used aqueous electrolytes to assemble a
fast charging, cost-efficient lithium aqueous battery that
still performs well.
Aqueous electrolytes have been
of interest for years because of
their non-flammable nature and
because they are not sensitive
to moisture in the manufacturing
process, making them easier to
work with and less expensive. The
biggest challenge with this material
has been maintaining performance.
“If you apply too much voltage
to water it electrolyzes, meaning the water breaks up into hydrogen
and oxygen,” said Nikhil Koratkar, professor of mechanical,
aerospace, and nuclear engineering at Rensselaer. “This is
a problem because then you get outgassing, and the electrolyte
is consumed. So usually, this material has a very limited voltage
window.”
Koratkar and his team used a water-in-salt electrolyte, which
is less likely to electrolyze. For the cathode, the researchers
used lithium manganese oxide, and for the anode, they used
niobium tungsten oxide, a complex oxide that has not been
explored in an aqueous battery before.
“It turns out that niobium tungsten oxide is outstanding in
terms of energy stored per
unit of volume,” said Koratkar.
“Volumetrically, this was by far
the best result that we have
seen in an aqueous lithium-ion
battery.” The cell has a volumetric
capacity of 200 Ah/l at
a 1C charging rate, which is
much higher than a state-of-art
graphite anode at 50 to 110
Ah/l.
The niobium tungsten oxide is relatively heavy and dense,
giving a good energy storage. The crystal structure also has
well-defined channels — or tunnels — that allow lithium ions
to diffuse quickly, meaning it can charge quickly. This combination
of fast-charging capability and the ability to store a
large amount of charge per unit volume is rare in an aqueous
battery. Koratkar sees the technology being used for portable
electronics, electric vehicles and grid storage.
Sidus teams with IBM for heavy metal-free battery design
By Rich Pell IBM Research, working with Chinese battery maker Sidus,
says it has discovered a chemistry for a new battery that
does not use heavy metals such as cobalt.
The chemistry, say the researchers, uses three new and
different proprietary materials that have never before been
recorded as being combined in a battery. The materials for
the battery are able to be extracted from seawater, laying the
groundwork for less invasive sourcing techniques than current
material mining methods. Sidus says it will lauch the battery
technology in 2020.
“Just as promising as this
new battery’s composition is its
performance potential,” says
IBM. “In initial tests, it proved it
can be optimized to surpass the
capabilities of lithium-ion batteries
in a number of individual categories
including lower costs, faster
charging time, higher power and
energy density, strong energy efficiency
and low flammability.”
The design uses a cobalt and
nickel-free cathode material, as
well as a safe liquid electrolyte with a high flash point. This combination
of cathode material and electrolyte, say the researchers,
demonstrated an ability to suppress lithium metal dendrites
during charging, thereby reducing flammability, which is widely
considered a significant drawback for the use of lithium metal
as an anode material.
IBM is working with Sidus, Mercedes-Benz Research and
Development North America and battery electrolyte supplier
Central Glass to create a battery development ecosystem
around the new technology.
“This discovery holds significant potential for electric vehicle
batteries, for example, where concerns such as flammability,
cost, and charging time come into play,” says the company.
“Current tests show that less than five minutes are required for
the battery – configured for high power – to reach an 80 percent
state of charge. Combined with the relatively low cost of sourcing
the materials, the goal of a fast-charging, low-cost electric
vehicle could become a reality.”
When optimized for very highpower
density - such as what will be
needed for flying vehicles and electric
aircrafts - the new battery design
exceeds more than 10,000 W/L,
outperforming the most powerful
lithium-ion batteries available. In addition,
say the researchers, tests have
shown this battery can be designed
for a long-life cycle, making it an option
for smart power grid applications
and new energy infrastructures where
longevity and stability is key.
Overall, according to the company, this battery has shown
the capacity to outperform existing lithium-ion batteries not only
in the previously listed applications, but can also be optimized
for a range of specific benefits. Looking ahead, the researchers
say they have also implemented an artificial intelligence (AI)
technique called semantic enrichment to further improve battery
performance by identifying safer and higher performance
materials.
28 News January 2020 @eeNewsEurope www.eenewseurope.com
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