New technique extends next-generation lithium metal batteries

Date:
November 4, 2020
Source:
Columbia University School of Engineering and Applied Science
Summary:
Engineering 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, and computational
modeling to discover that adding small amounts of potassium salt
to a conventional lithium battery electrolyte produces unique
chemistry at the lithium/electrolyte interface, and modulates
degradation during battery operation, preventing the growth of
microstructures and leading to safer, longer lasting batteries.



FULL STORY ========================================================================== Electric vehicles (EVs) hold great promise for our energy-efficient, sustainable future but among their limitations is the lack of a
long-lasting, high energy density battery that reduces the need to fuel up
on long-haul 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. Next-generation lithium batteries that offer lightweight, long-lasting, and low-cost
energy storage could revolutionize the industry but there have been a
host of challenges that have prevented successful commercialization.


==========================================================================
A major issue is that while rechargeable lithium metal anodes play
a key role in how well this new wave of lithium batteries function,
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 at Columbia Engineering report today that they 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 lithium/electrolyte interface. The study is
published online today in Cell Reports Physical Science (and in the
November 18th print edition).

"Specifically, we 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," says the team's
PI Lauren Marbella, assistant professor of chemical engineering.

Her team's discovery that alkali metal additives suppress the growth of
non- conductive compounds on the surface of lithium metal differs from traditional electrolyte manipulation approaches, which have focused on depositing conductive polymers on the metal's surface. The work is one
of the first in- depth characterizations of the surface chemistry of
lithium metal using NMR, and demonstrates the power of this technique
to design new electrolytes for lithium metal. Marbella's results were complemented with density functional theory (DFT) calculations performed
by collaborators in the Viswanathan group in mechanical engineering at
Carnegie Mellon University.

"Commercial electrolytes are a cocktail of carefully selected molecules," Marbella notes. "Using NMR and computer simulations, we can finally
understand how these unique electrolyte formulations improve lithium
metal battery performance at the molecular level. This insight ultimately
gives researchers the tools they need to optimize electrolyte design and
enable stable lithium metal batteries." The team is now testing alkali
metal additives that stop the formation of deleterious surface layers
in combination with more traditional additives that encourage the growth
of conductive layers on lithium metal. They are also actively using NMR
to directly measure the rate of lithium transport through this layer.


========================================================================== Story Source: Materials provided by Columbia_University_School_of_Engineering_and_Applied Science. Original
written by Holly Evarts. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Richard May, Yumin Zhang, Steven R. Denny, Venkatasubramanian
Viswanathan, Lauren E. Marbella. Leveraging Cation Identity
to Engineer Solid Electrolyte Interphases for Rechargeable
Lithium Metal Anodes. Cell Reports Physical Science, 2020 DOI:
10.1016/j.xcrp.2020.100239 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/11/201104114743.htm

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