Faster, more efficient energy storage could stem from holistic study of layered materials

Date:
August 25, 2020
Source:
DOE/Oak Ridge National Laboratory
Summary:
A team has developed a novel, integrated approach to track energy-
transporting ions within an ultra-thin material, which could
unlock its energy storage potential leading toward faster charging,
longer lasting devices.



FULL STORY ==========================================================================
A team led by the Department of Energy's Oak Ridge National Laboratory developed a novel, integrated approach to track energy-transporting ions
within an ultra-thin material, which could unlock its energy storage
potential leading toward faster charging, longer lasting devices.


========================================================================== Scientists have for a decade studied the energy-storing possibilities
of an emerging class of two-dimensional materials -- those constructed
in layers that are only a few atoms thick -- called MXenes, pronounced "max-eens." The ORNL-led team integrated theoretical data from
computational modeling of experimental data to pinpoint potential
locations of a variety of charged ions in titanium carbide, the most
studied MXene phase. Through this holistic approach, they could track
and analyze the ions' motion and behavior from the single-atom to the
device scale.

"By comparing all the methods we employed, we were able to form links
between theory and different types of materials characterization, ranging
from very simple to very complex over a wide range of length and time
scales," said Nina Balke, ORNL co-author of the published study that was conducted within the Fluid Interface Reactions, Structures and Transport,
or FIRST, Center. FIRST is a DOE-funded Energy Frontier Research Center
located at ORNL.

"We pulled all those links together to understand how ion storage works
in layered MXene electrodes," she added. The study's results allowed
the team to predict the material's capacitance, or its ability to
store energy. "And, in the end, after much discussion, we were able to
unify all these techniques into one cohesive picture, which was really
cool." Layered materials can enhance energy stored and power delivered
because the gaps between the layers allow charged particles, or ions,
to move freely and quickly. However, ions can be difficult to detect
and characterize, especially in a confined environment with multiple
processes at play. A better understanding of these processes can advance
the energy storage potential of lithium-ion batteries and supercapacitors.

As a FIRST center project, the team focused on the development of supercapacitors -- devices that charge quickly for short-term, high-power energy needs. In contrast, lithium-ion batteries have a higher energy
capacity and provide electrical power longer, but the rates of discharge,
and therefore their power levels, are lower.

MXenes have the potential to bridge the benefits of these two concepts,
Balke said, which is the overarching goal of fast-charging devices with greater, more efficient energy storage capacity. This would benefit a
range of applications from electronics to electric vehicle batteries.

Using computational modeling, the team simulated the conditions of five different charged ions within the layers confined in an aqueous solution,
or "water shell." The theoretical model is simple, but combined with experimental data, it created a baseline that provided evidence of
where the ions within the MXene layers went and how they behaved in a
complex environment.

"One surprising outcome was we could see, within the simulation limits, different behavior for the different ions," said ORNL theorist and
co-author Paul Kent.

The team hopes their integrated approach can guide scientists toward
future MXene studies. "What we developed is a joint model. If we have a
little bit of data from an experiment using a certain MXene, and if we
knew the capacitance for one ion, we can predict it for the other ones,
which is something that we weren't able to do before," Kent said.

"Eventually, we'll be able to trace those behaviors to more real-world, observable changes in the material's properties," he added.


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


========================================================================== Journal Reference:
1. Qiang Gao, Weiwei Sun, Poorandokht Ilani-Kashkouli, Alexander
Tselev,
Paul R. C. Kent, Nadine Kabengi, Michael Naguib, Mohamed Alhabeb,
Wan-Yu Tsai, Arthur P. Baddorf, Jingsong Huang, Stephen Jesse, Yury
Gogotsi, Nina Balke. Tracking ion intercalation into layered Ti3C2
MXene films across length scales. Energy & Environmental Science,
2020; 13 (8): 2549 DOI: 10.1039/D0EE01580F ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200825110650.htm

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