Engineers produce the world's longest flexible fiber battery
The rechargeable battery can be woven and washed, and could provide power
for fiber-based electronic devices and sensors.

Date:
December 20, 2021
Source:
Massachusetts Institute of Technology
Summary:
Researchers have developed a rechargeable lithium-ion battery in
the form of ultra-long fiber that could be woven into fabrics. The
battery could enable a wide variety of wearable electronic devices,
and might even be used to make 3D-printed batteries in virtually
any shape.



FULL STORY ========================================================================== Researchers have developed a rechargeable lithium-ion battery in the form
of an ultra-long fiber that could be woven into fabrics. The battery
could enable a wide variety of wearable electronic devices, and might
even be used to make 3D- printed batteries in virtually any shape.


==========================================================================
The researchers envision new possibilities for self-powered
communications, sensing, and computational devices that could be worn
like ordinary clothing, as well as devices whose batteries could also
double as structural parts.

In a proof of concept, the team behind the new battery technology has
produced the world's longest flexible fiber battery, 140 meters long,
to demonstrate that the material can be manufactured to arbitrarily long lengths. The work is described today in the journal Materials Today.MIT
postdoc Tural Khudiyev (now an assistant professor at National University
of Singapore), former MIT postdoc Jung Tae Lee (now a professor at Kyung
Hee University), and Benjamin Grena SM '13, PhD '17 (currently at Apple)
are the lead authors on the paper. Other co- authors are MIT professors
Yoel Fink, Ju Li, and John Joannopoulos, and seven others at MIT and
elsewhere.

Researchers, including members of this team, have previously demonstrated fibers that contain a wide variety of electronic components, including
light emitting diodes (LEDs), photosensors, communications, and digital systems. Many of these are weavable and washable, making them practical
for use in wearable products, but all have so far relied on an external
power source. Now, this fiber battery, which is also weavable and
washable, could enable such devices to be completely self-contained.

The new fiber battery is manufactured using novel battery gels and
a standard fiber-drawing system that starts with a larger cylinder
containing all the components and then heats it to just below its melting point. The material is drawn through a narrow opening to compress all
the parts to a fraction of their original diameter, while maintaining
all the original arrangement of parts.

While others have attempted to make batteries in fiber form, Khudiyev
says, those were structured with key materials on the outside of the
fiber, whereas this system embeds the lithium and other materials inside
the fiber, with a protective outside coating, thus directly making
this version stable and waterproof. This is the first demonstration of sub-kilometer long fiber battery which is both sufficiently long and
highly durable to have practical applications, he says.



==========================================================================
The fact that they were able to make a 140-meter fiber battery shows
that "there's no obvious upper limit to the length. We could definitely
do a kilometer-scale length," he says. A demonstration device using
the new fiber battery incorporated a "Li-Fi" communications system --
one in which pulses of light are used to transmit data, and included
a microphone, pre-amp, transistor, and diodes to establish an optical
data link between two woven fabric devices.

"When we embed the active materials inside the fiber, that means sensitive battery components already have a good sealing," Khudiyev says, "and all
the active materials are very well-integrated, so they don't change their position" during the drawing process. In addition, the resulting fiber
battery is much thinner and more flexible yielding an aspect ratio,
that is the length-to-width fraction, up to a million, which is way
beyond other designs, which makes it practical to use standard weaving equipment to create fabrics that incorporate the batteries as well as electronic systems.

The 140-meter fiber produced so far has an energy storage capacity of 123 milliamp-hours, which can charge smartwatches or phones, he says. The
fiber device is only a few hundred microns in thickness, thinner than
any previous attempts to produce batteries in fiber form.

"The beauty of our approach is that we can embed multiple devices in
an individual fiber, Lee says, "unlike other approaches which need
integration of multiple fiber devices." They demonstrated integration
of LED and Li-ion battery in a single fiber and he believes more than
three or four devices can be combined in such a small space in the
future. "When we integrate these fibers containing multi-devices, the
aggregate will advance the realization of a compact fabric computer."
In addition to individual one-dimensional fibers, which can be woven
to produce two-dimensional fabrics, the material can also be used in 3D printing or custom-shape systems to create solid objects, such as casings
that could provide both the structure of a device and its power source. To demonstrate this capability, a toy submarine was wrapped with the battery
fiber to provide it with power. Incorporating the power source into the structure of such devices could lower the overall weight and so improve
the efficiency and range they can achieve.

"This is the first 3D printing of a fiber battery device," Khudiyev
says. "If you want to make complex objects" through 3D printing that incorporate a battery device, he says, this is the first system that can achieve that. "After printing, you do not need to add anything else,
because everything is already inside the fiber, all the metals, all
the active materials. It's just a one- step printing. That's a first."
That means that now, he says, "Computational units can be put inside
everyday objects, including Li-Fi." The team has already applied for
a patent on the process and continues to develop further improvements
in power capacity and variations on the materials used to improve
efficiency. Khudiyev says such fiber batteries could be ready for use
in commercial products within a few years.

The research was supported by the MIT MRSEC program of the National
Science Foundation, the U.S. Army Research Laboratory through the
Institute for Soldier Nanotechnologies, the National Science Foundation's graduate research fellowship program, and the National Research Foundation
of Korea.

========================================================================== Story Source: Materials provided by
Massachusetts_Institute_of_Technology. Original written by David
L. Chandler. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Tural Khudiyev, Benjamin Grena, Gabriel Loke, Chong Hou, Hyeonji
Jang,
Jinhyuk Lee, Grace H. Noel, Juliette Alain, John Joannopoulos, Kang
Xu, Ju Li, Yoel Fink, Jung Tae Lee. Thermally drawn rechargeable
battery fiber enables pervasive power. Materials Today, 2021; DOI:
10.1016/ j.mattod.2021.11.020 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/12/211220131314.htm

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