Stretching the capacity of flexible energy storage

Date:
September 8, 2021
Source:
American Chemical Society
Summary:
Some electronics can bend, twist and stretch in wearable displays,
biomedical applications and soft robots. While these devices'
circuits have become increasingly pliable, the batteries
and supercapacitors that power them are still rigid. Now,
researchersreport a flexible supercapacitor with electrodes made
of wrinkled titanium carbide -- a type of MXene nanomaterial --
that maintained its ability to store and release electronic charges
after repetitive stretching.



FULL STORY ==========================================================================
Some electronics can bend, twist and stretch in wearable displays,
biomedical applications and soft robots. While these devices' circuits
have become increasingly pliable, the batteries and supercapacitors that
power them are still rigid. Now, researchers in ACS' Nano Letters report a flexible supercapacitor with electrodes made of wrinkled titanium carbide
-- a type of MXene nanomaterial -- that maintained its ability to store
and release electronic charges after repetitive stretching.


==========================================================================
One major challenge stretchable electronics must overcome is the stiff
and inflexible nature of their energy storage components, batteries
and supercapacitors. Supercapacitors that use electrodes made from
transitional metal carbides, carbonitrides or nitrides, called MXenes,
have desirable electrical properties for portable flexible devices, such
as rapid charging and discharging. And the way that 2D MXenes can form multi-layered nanosheets provides a large surface area for energy storage
when they're used in electrodes. However, previous researchers have had
to incorporate polymers and other nanomaterials to keep these types of electrodes from breaking when bent, which decreases their electrical
storage capacity. So, Desheng Kong and colleagues wanted to see if
deforming a pristine titanium carbide MXene film into accordion-like
ridges would maintain the electrode's electrical properties while adding flexibility and stretchability to a supercapacitor.

The researchers disintegrated titanium aluminum carbide powder into
flakes with hydrofluoric acid and captured the layers of pure titanium
carbide nanosheets as a roughly textured film on a filter. Then they
placed the film on a piece of pre-stretched acrylic elastomer that was
800% its relaxed size. When the researchers released the polymer, it
shrank to its original state, and the adhered nanosheets crumpled into accordion-like wrinkles.

In initial experiments, the team found the best electrode was made from a
3 mym-thick film that could be repetitively stretched and relaxed without
being damaged and without modifying its ability to store an electrical
charge. The team used this material to fabricate a supercapacitor by sandwiching a polyvinyl(alcohol)-sulfuric acid gel electrolyte between
a pair of the stretchable titanium carbide electrodes. The device had a
high energy capacity comparable to MXene-based supercapacitors developed
by other researchers, but it also had extreme stretchability up to 800%
without the nanosheets cracking.

It maintained approximately 90% of its energy storage capacity after being stretched 1,000 times, or after being bent or twisted. The researchers
say their supercapacitor's excellent energy storage and electrical
stability is attractive for stretchable energy storage devices and
wearable electronic systems.

The authors acknowledge funding from the Key Research and Development
Program of Jiangsu Provincial Department of Science and Technology
of China, China Postdoctoral Science Foundation and High-Level
Entrepreneurial and Innovative Talents Program of Jiangsu Province.

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


========================================================================== Journal Reference:
1. Shuxuan Feng, Xin Wang, Menglu Wang, Chong Bai, Shitai Cao,
Desheng Kong.

Crumpled MXene Electrodes for Ultrastretchable and
High-Area-Capacitance Supercapacitors. Nano Letters, 2021; DOI:
10.1021/acs.nanolett.1c02071 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/09/210908084018.htm

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