The atomic processes that make a family of chemicals known as argyrodites
appealing candidates for both solid-state battery electrolytes and
thermoelectric energy converters have been discovered by a research team at
Duke University and its partners.
The findings, along with the machine learning strategy that led to them,
may herald in a new era of energy storage for uses like home battery walls
and quick-charging electric vehicles.
The findings were published online in the journal Nature Materials on May
18.
Given the size and complexity of each component of the material, Olivier
Delaire, an associate professor of mechanical engineering and materials
science at Duke, remarked, "This is a puzzle that has not been solved
before." We've uncovered the atomic-level mechanics behind this class of
materials' current popularity in the field of solid-state battery
advancement.
Researchers must create new technologies for energy storage and
distribution to households and electric cars as the world moves toward an
energy future based on renewable sources. The lithium-ion battery with
liquid electrolytes has been the industry standard up to this point,
although it is far from the best option due to its low efficiency and
propensity for spontaneous combustion and explosion.
These restrictions are mostly caused by the chemically reactive liquid
electrolytes used within Li-ion batteries, which allow lithium ions to
travel between electrodes relatively unhindered. The liquid component makes
them vulnerable to high temperatures, which can lead to degeneration and,
finally, a runaway thermal disaster, despite the fact that they are
excellent for transporting electric charges.
A lot of effort and money is being invested by both public and commercial
research institutes in the development of alternative solid-state batteries
made of various materials. In principle, this strategy produces a device
that is considerably safer, more stable, and has a larger energy density if
it is properly constructed.
While no economically feasible method for solid-state batteries has yet
been found, one of the top candidates is based on a group of substances
known as argyrodites, which take their name from a mineral that contains
silver. These compounds are composed of two distinct, stable crystalline
frameworks with room for a third element to move freely inside the chemical
structure. While some ingredients, like silver, germanium, and sulfur, are
found in nature, the overall structure is open-ended enough for scientists
to come up with a broad range of combinations.
Every manufacturer of electric vehicles is attempting to switch to new
solid-state battery designs, but none of them have revealed which
compositions they are placing their bets on, according to Delaire. "Winning
that race would be a game-changer because cars could charge faster, last
longer, and be safer all at once."
In the current article, Delaire and his coworkers examine a promising
possibility called Ag8SnSe6, which is formed of silver, tin, and selenium.
The molecular behavior of samples of Ag8SnSe6 was revealed in real-time by
the researchers using a combination of neutrons and X-rays to bounce these
incredibly fast-moving particles off atoms within the samples. Using
first-principles quantum mechanical simulations, team member Mayanak Gupta,
a former postdoc in Delaire's lab who is now a researcher at the Bhabha
Atomic Research Center in India, developed a computational model to match
the observations. She also developed a machine learning strategy to make
sense of the data.
The outcomes demonstrated that although the scaffolding made by the tin and
selenium atoms was rather stable, it wasn't static. In order to allow the
charged silver ions to freely travel through the substance, the crystalline
structure continually bends to form windows and channels. Delaire described
the system as having tin and selenium lattices that are still solid and
silver that is practically liquid-like.
Delaire described the movement of the silver atoms as resembling marbles
rattling about the bottom of a very shallow well, as if the crystalline
scaffold weren't a solid structure. What really surprised me was that a
substance could exist in both a liquid and a solid form.
The findings and, perhaps more crucially, the method of replacing
lithium-ion batteries in many essential applications by combining superior
experimental spectroscopy with machine learning, should speed up research in
this area. Delaire claims that this study is only one in a series of
initiatives aiming at various potential argyrodite compounds made up of
various recipes. Due to its potential for use in EV batteries, one
combination that uses lithium instead of silver is of special interest to
the group.
We are carefully examining the complete family of compounds since many of
these materials provide extremely quick conduction for batteries while also
serving as effective heat insulators for thermoelectric converters,
according to Delaire. "This work serves as a benchmark for our machine
learning methodology, which has greatly improved our capacity to mimic these
materials in just a few years. As a result, I think we'll be able to swiftly
recreate new chemicals realistically and discover the greatest recipes they
have to offer.
Provided by
Duke University
