https://www.eurekalert.org/pub_releases/2018-04/uarl-arr041718.php
Army research rejuvenates older zinc batteries
17-Apr-2018  U.S. Army Research Laboratory

[image  / Artwork by Eric Proctor
https://media.eurekalert.org/multimedia_prod/pub/web/168210_web.jpg
An artist's conception of a zinc ion that has been fully surrounded by
anions in the super-concentrated electrolyte is trying to break out of the
binding and deposit on zinc metal surface in a controlled and smooth manner
]

ADELPHI, MD. -- Army scientists, with a team of researchers from the
University of Maryland and the National Institute of Standards and
Technology, have created a water-based zinc battery that is simultaneously
powerful, rechargeable and intrinsically safe.

The high-impact journal Nature Materials published a peer-reviewed paper
based on this ground-breaking research April 16.

In prior achievements, these scientists invented a new class of water-based
electrolytes that can work under extreme electrochemical conditions that
ordinary water cannot, and have successfully applied it on different
lithium-ion chemistries. In this work, they adapted the electrolyte to a
battery chemistry much cheaper than lithium: Zinc, and they demonstrated
that an aqueous battery can satisfy the multi-facet goals of high energy,
high safety and low cost simultaneously.

The world's very first battery used zinc as anode in 1799. In the following
two centuries, many zinc-based batteries were commercialized, some of which
are still on market. These batteries used to provide safe and reliable
energy, although at moderate energy density, to satisfy our daily needs, but
their presence in our lives has significantly shrunken since the emergence
of lithium-ion batteries 28 years ago. Besides energy density, a major
reason for the diminishing role of zinc batteries is the poor reversibility
of the zinc chemistry in aqueous electrolytes. Non-rechargeable batteries
already created significant amount of landfill, imposing serious
environmental burden on industrialized societies.

"On the other hand, with increasing presence of lithium-ion batteries in our
lives, from portable electronics to electric vehicles, their safety raises
more public concerns, from Tesla car fires to the global grounding of the
entire Boeing 787 fleet," explained Dr. Kang Xu, who is an ARL fellow and
team leader, and co-corresponding authors of this paper. "The safety hazard
of lithium-ion batteries are rooted in the highly flammable and toxic
non-aqueous electrolytes used therein. The batteries of aqueous nature thus
become attractive, if they can be made rechargeable with high energy
densities. Zinc is a natural candidate."

The researchers said the new aqueous zinc battery could eventually be used
not just in consumer electronics, but also in extreme conditions to improve
the performance of safety-critical vehicles such as those used in aerospace,
military and deep-ocean environments.

As an example of the aqueous zinc battery's power and safety, Fei Wang, a
jointly appointed postdoctoral associate at UMD's Clark School and ARL, and
first author of the paper, cites the numerous battery fire incidents in cell
phones, laptops and electric cars highlighted in recent media coverage. The
new aqueous zinc battery presented in this work could be the answer to the
call for safe battery chemistry while still maintaining the comparable or
even higher energy densities of conventional lithium-ion batteries.

"Water-based batteries could be crucial to preventing fires in electronics,
but their energy storage and capacity have been limited -- until now. For
the first time, we have a battery that could compete with the lithium-ion
batteries in energy density, but without the risk of explosion or fire,"
Wang said.

This highly concentrated aqueous zinc battery also overcomes other
disadvantages of conventional zinc batteries, such as the capacity to endure
only limited recharging cycles, dendrite (tree-like structures of crystals)
growth during usage and recharging, and sustained water consumption,
resulting in the need to regularly replenishing the batteries' electrolyte
with water.

"Existing zinc batteries are safe and relatively inexpensive to produce, but
they aren't perfect due to poor cycle life and low energy density. We
overcome these challenges by using a water-in-salt electrolyte," says
Chunsheng Wang, UMD professor of chemical and biomolecular engineering and
corresponding author of the paper.

The research team says this battery technology advance lays the groundwork
for further research, and they are hopeful for possible future
commercialization.

"The significant discovery made in this work has touched the core problem of
aqueous zinc batteries, and could impact other aqueous or non-aqueous
multivalence cation chemistries that face similar challenges, such as
magnesium and aluminum batteries", Xu said. "A much more difficult challenge
is, of course, the reversibility of lithium metal, which faces similar but
much more difficult challenges."

Resolution of lithium-metal deposition could unlock the "Holy Grail" of all
batteries, which is the area where these scientists are closely working on
with the scientists at the Department of Energy, he said.

###
The research received funding support from the Department of Energy Advanced
Research Projects Agency-Energy and the University of Maryland Center for
Research in Extreme Batteries.

The authors acknowledged additional support from the University of Maryland
NanoCenter.

The paper, "Highly reversible zinc metal anode for aqueous batteries," Wang,
F., Borodin, O., Gao, T., Fan, X., Sun, W., Han, F. ... Wang, C., published
online April 16 in the journal Nature Materials. DOI:
10.1038/s41563-018-0063-z

The U.S. Army Research Laboratory is part of the U.S. Army Research,
Development and Engineering Command, which has the mission to ensure
decisive overmatch for unified land operations to empower the Army, the
joint warfighter and our nation. RDECOM is a major subordinate command of
the U.S. Army Materiel Command.
[© 2018 American Association for the Advancement of Science (AAAS)]




https://www.sciencedaily.com/releases/2018/04/180417155605.htm
Rejuvenating older zinc batteries
Date:    April 17, 2018
Source:  U.S. Army Research Laboratory
Summary: Scientists have created a water-based zinc battery that is
simultaneously powerful, rechargeable and intrinsically safe. 

FULL STORY
Army scientists, with a team of researchers from the University of Maryland
and the National Institute of Standards and Technology, have created a
water-based zinc battery that is simultaneously powerful, rechargeable and
intrinsically safe.

The high-impact journal Nature Materials published a peer-reviewed paper
based on this ground-breaking research April 16.

In prior achievements, these scientists invented a new class of water-based
electrolytes that can work under extreme electrochemical conditions that
ordinary water cannot, and have successfully applied it on different
lithium-ion chemistries. In this work, they adapted the electrolyte to a
battery chemistry much cheaper than lithium: Zinc, and they demonstrated
that an aqueous battery can satisfy the multi-facet goals of high energy,
high safety and low cost simultaneously.

The world's very first battery used zinc as anode in 1799. In the following
two centuries, many zinc-based batteries were commercialized, some of which
are still on market. These batteries used to provide safe and reliable
energy, although at moderate energy density, to satisfy our daily needs, but
their presence in our lives has significantly shrunken since the emergence
of lithium-ion batteries 28 years ago. Besides energy density, a major
reason for the diminishing role of zinc batteries is the poor reversibility
of the zinc chemistry in aqueous electrolytes. Non-rechargeable batteries
already created significant amount of landfill, imposing serious
environmental burden on industrialized societies.

"On the other hand, with increasing presence of lithium-ion batteries in our
lives, from portable electronics to electric vehicles, their safety raises
more public concerns, from Tesla car fires to the global grounding of the
entire Boeing 787 fleet," explained Dr. Kang Xu, who is an ARL fellow and
team leader, and co-corresponding authors of this paper. "The safety hazard
of lithium-ion batteries are rooted in the highly flammable and toxic
non-aqueous electrolytes used therein. The batteries of aqueous nature thus
become attractive, if they can be made rechargeable with high energy
densities. Zinc is a natural candidate."

The researchers said the new aqueous zinc battery could eventually be used
not just in consumer electronics, but also in extreme conditions to improve
the performance of safety-critical vehicles such as those used in aerospace,
military and deep-ocean environments.

As an example of the aqueous zinc battery's power and safety, Fei Wang, a
jointly appointed postdoctoral associate at UMD's Clark School and ARL, and
first author of the paper, cites the numerous battery fire incidents in cell
phones, laptops and electric cars highlighted in recent media coverage. The
new aqueous zinc battery presented in this work could be the answer to the
call for safe battery chemistry while still maintaining the comparable or
even higher energy densities of conventional lithium-ion batteries.

"Water-based batteries could be crucial to preventing fires in electronics,
but their energy storage and capacity have been limited -- until now. For
the first time, we have a battery that could compete with the lithium-ion
batteries in energy density, but without the risk of explosion or fire,"
Wang said.

This highly concentrated aqueous zinc battery also overcomes other
disadvantages of conventional zinc batteries, such as the capacity to endure
only limited recharging cycles, dendrite (tree-like structures of crystals)
growth during usage and recharging, and sustained water consumption,
resulting in the need to regularly replenishing the batteries' electrolyte
with water.

"Existing zinc batteries are safe and relatively inexpensive to produce, but
they aren't perfect due to poor cycle life and low energy density. We
overcome these challenges by using a water-in-salt electrolyte," says
Chunsheng Wang, UMD professor of chemical and biomolecular engineering and
corresponding author of the paper.

The research team says this battery technology advance lays the groundwork
for further research, and they are hopeful for possible future
commercialization.

"The significant discovery made in this work has touched the core problem of
aqueous zinc batteries, and could impact other aqueous or non-aqueous
multivalence cation chemistries that face similar challenges, such as
magnesium and aluminum batteries," Xu said. "A much more difficult challenge
is, of course, the reversibility of lithium metal, which faces similar but
much more difficult challenges."

Resolution of lithium-metal deposition could unlock the "Holy Grail" of all
batteries, which is the area where these scientists are closely working on
with the scientists at the Department of Energy, he said.
[© 2018 ScienceDaily]


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