New material could pave the way for better, safer batteries

Date:
October 21, 2021
Source:
Brown University
Summary:
A material derived from trees could potentially replace liquid
electrolytes in next-generation batteries.



FULL STORY ==========================================================================
In pursuit of batteries that deliver more power and operate more
safely, researchers are working to replace the liquids commonly used
in today's lithium ion batteries with solid materials. Now, a research
team from Brown University and the University of Maryland has developed
a new material for use in solid- state batteries that's derived from an unlikely source: trees.


==========================================================================
In research published in the journal Nature, the team demonstrates a solid
ion conductor that combines copper with cellulose nanofibrils -- polymer
tubes derived from wood. The paper-thin material has an ion conductivity
that is 10 to 100 times better than other polymer ion conductors, the researchers say. It could be used as either a solid battery electrolyte or
as an ion-conducting binder for the cathode of an all-solid-state battery.

"By incorporating copper with one-dimensional cellulose nanofibrils,
we demonstrated that the normally ion-insulating cellulose offers a
speedier lithium-ion transport within the polymer chains," said Liangbing
Hu, a professor in the University of Maryland's Department of Materials
Science and Engineering. "In fact, we found this ion conductor achieved
a record high ionic conductivity among all solid polymer electrolytes."
The work was a collaboration between Hu's lab and the lab of Yue Qi,
a professor at Brown's School of Engineering.

Today's lithium ion batteries, which are widely used in everything from cellphones to cars, have electrolytes made from lithium salt dissolved in
a liquid organic solvent. The electrolyte's job is to conduct lithium ions between a battery's cathode and anode. Liquid electrolytes work pretty
well, but they have some downsides. At high currents, tiny filaments of
lithium metal, called dendrites, can form in the electrolyte leading to
short circuits.

In addition, liquid electrolytes are made with flammable and toxic
chemicals, which can catch fire.

Solid electrolytes have the potential to prevent dendrite penetration
and can be made from non-flammable materials. Most of the solid
electrolytes investigated so far are ceramic materials, which are great
at conducting ions but they're also thick, rigid and brittle. Stresses
during manufacturing as well as charging and discharging can lead to
cracks and breaks.

The material introduced in this study, however, is thin and flexible,
almost like a sheet of paper. And its ion conductivity is on par with
ceramics.

Qi and Qisheng Wu, a senior research associate at Brown, performed
computer simulations of the microscopic structure of the copper-cellulose material to understand why it is able to conduct ions so well. The
modeling study revealed that the copper increases the space between
cellulose polymer chains, which normally exist in tightly packed
bundles. The expanded spacing creates what amount to ion superhighways
through which lithium ions can zip by relatively unimpeded.

"The lithium ions move in this organic solid electrolyte via mechanisms
that we typically found in inorganic ceramics, enabling the record
high ion conductivity," Qi said. "Using materials nature provides will
reduce the overall impact of battery manufacture to our environment."
In addition to working as a solid electrolyte, the new material can also
act as a cathode binder for a solid-state battery. In order to match
the capacity of anodes, cathodes need to be substantially thicker. That thickness, however, can compromise ion conduction, reducing efficiency. In order for thicker cathodes to work, they need to be encased in an ion-conducting binder. Using their new material as a binder, the team demonstrated what they believe to be one of the thickest functional
cathodes ever reported.

The researchers are hopeful that the new material could be a step toward
making bringing solid state battery technology to the mass market.

The research at Brown University was supported by the National Science Foundation (DMR-2054438).

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


========================================================================== Journal Reference:
1. Chunpeng Yang, Qisheng Wu, Weiqi Xie, Xin Zhang, Alexandra
Brozena, Jin
Zheng, Mounesha N. Garaga, Byung Hee Ko, Yimin Mao, Shuaiming
He, Yue Gao, Pengbo Wang, Madhusudan Tyagi, Feng Jiao, Robert
Briber, Paul Albertus, Chunsheng Wang, Steven Greenbaum, Yan-Yan
Hu, Akira Isogai, Martin Winter, Kang Xu, Yue Qi, Liangbing
Hu. Copper-coordinated cellulose ion conductors for solid-state
batteries. Nature, 2021; DOI: 10.1038/s41586-021-03885-6 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/10/211021175142.htm

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