Thin layer protects battery, allows cold charging

Date:
August 26, 2020
Source:
Penn State
Summary:
In the search for a reliable, quick-charging, cold-weather battery
for automobiles, a self-assembling, thin layer of electrochemically
active molecules may be the solution, according to a team or
researchers.



FULL STORY ==========================================================================
In the search for a reliable, quick-charging, cold-weather battery for automobiles, a self-assembling, thin layer of electrochemically active molecules may be the solution, according to a team or researchers.


==========================================================================
"The lithium metal battery is the next generation of battery after
the lithium ion battery," said Donghai Wang, professor of mechanical engineering and a key researcher in the Battery and Energy Storage
Technology Center, Penn State. "It uses a lithium anode and has higher
energy density, but has problems with dendritic growth, low efficiency
and low cycle life." The solution to these problems, according to the researchers, is a self- assembling monolayer that is electrochemically
active so that it can decompose into its proper components and protect
the surface of the lithium anode.

The battery is composed of the lithium anode, a lithium metal oxide
cathode and an electrolyte which also has lithium-ion conducting materials
and the protective, thin film layer. Without this layer, the battery
would tend to grow lithium crystal spikes if charged rapidly or under
cold conditions. These lithium spikes eventually short out the battery,
greatly decreasing the usefulness and cycle life.

"The key is to tune the molecular chemistry to self-assemble on the
surface," said Wang. "The monolayer will provide a good solid electrolyte interface when charging, and protect the lithium anode." The researchers deposit the monolayer on a thin copper layer. When the battery charges,
lithium hits the monolayer and decomposes to form a stable interfacial
layer. Some lithium is deposited on the copper along with the remaining
layer, and the decomposed portion of the original layer reforms on top of
the lithium, protecting the lithium and preventing dendrites of lithium
from forming.

According to the researchers, this technology can increase the amount
of storage capacity of the battery and can increase the number of times
the battery can be charged. However, at this point, the battery can only
be charged a few hundred times. The researchers reported their work in
a recent issue of Nature Energy.

"The key is that this technology shows an ability to form a layer
when needed on time and decompose and spontaneously reform so it will
stay on the copper and also cover the surface of the lithium," said
Wang. "Eventually it could be used for drones, cars, or some very small batteries used for underwater applications at low temperatures.


========================================================================== Story Source: Materials provided by Penn_State. Original written by
A'ndrea Elyse Messer.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Yue Gao, Tomas Rojas, Ke Wang, Shuai Liu, Daiwei Wang, Tianhang
Chen,
Haiying Wang, Anh T. Ngo, Donghai Wang. Low-temperature and
high-rate- charging lithium metal batteries enabled by an
electrochemically active monolayer-regulated interface. Nature
Energy, 2020; 5 (7): 534 DOI: 10.1038/s41560-020-0640-7 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200826083031.htm

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