Researchers 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 portable electronic devices and could even be used to make 3D printed batteries in virtually any shape.
Researchers envision new possibilities for self-powered communication, sensing and computing devices that could be worn like ordinary clothing, as well as devices whose batteries could also serve as structural parts.
In a proof of concept, the team behind the new battery technology 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 Postdoctoral Fellow Tural Khudiyev (now Assistant Professor at National University of Singapore), Former MIT Postdoctoral Fellow Jung Tae Lee (now Professor at Kyung Hee University) and Benjamin Grena SM ’13, PhD ’17 (currently at Apple) are the main authors on paper. The 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 already demonstrated fibers containing a wide variety of electronic components, including light-emitting diodes (LEDs), photosensors, communications, and digital systems. Many of them are woven and washable, making them convenient for use in wearable products, but all have so far relied on an external power source. However, this fiber battery, also braid and washable, could allow such devices to be completely autonomous.
The new fiber battery is made using new battery gels and a standard fiber drawing system that starts with a larger cylinder containing all of the components and then heats it to just below its melting point. Material is sucked through a narrow opening to compress all parts to a fraction of their original diameter, while retaining all of the original arrangement of the parts.
While others have attempted to make batteries in fiber form, says Khudiyev, these were structured with key materials on the outside of the fiber, while this system incorporates lithium and other materials into the fiber. ‘inside the fiber, with a protective outer coating, which directly makes this stable and waterproof version. This is the first demonstration of a less than kilometer long fiber battery that is both long enough and very durable to have practical applications, he says.
The fact that they were able to manufacture a 140 meter fiber battery shows that “there is no obvious upper limit to the length. We could definitely do a kilometer scale length, ”he said. A demonstration device using the new fiber-optic battery incorporated a ‘Li-Fi’ communication system – a system in which pulses of light are used to transmit data, and included a microphone, preamplifier, transistor, and diodes to transmit data. establish an optical data link between two woven fabric devices.
“When we integrate the active materials inside the fiber, it means that the sensitive components of the battery already have a good seal,” explains Khudiyev, “and all the active materials are integrated very well, so they don’t change. position “during the drawing process. In addition, the resulting fiber battery is much thinner and more flexible resulting in an aspect ratio, i.e. the length-to-width fraction, of up to one million, which is much higher. beyond other designs, making it convenient to use standard weaving equipment to create fabrics that incorporate batteries as well as electronic systems.
The 140-meter fiber produced so far has an energy storage capacity of 123 milliampere-hours, which can charge smartwatches or phones, he says. The fiber device is only a few hundred microns thick, thinner than any previous attempt to produce batteries as fiber.
“The beauty of our approach is that we can integrate multiple devices into an individual fiber,” says Lee, “unlike other approaches that require the integration of multiple fiber devices. They demonstrated the integration of LEDs and Li-ion batteries into a single fiber and he believes that 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 the individual one-dimensional fibers, which can be woven to produce two-dimensional fabrics, the material can also be used in 3D printing systems or custom shapes to create solid objects, such as envelopes that could provide both the structure of a device and its power source. To demonstrate this ability, a toy submarine was wrapped with battery fiber to provide it with power. Integrating the power source into the structure of such devices could reduce the overall weight and thus improve the efficiency and range they can achieve.
“This is the first 3D printing of a fiber battery device,” says Khudiyev. “If you want to make complex objects” with 3D printing that incorporates a battery device, he says, this is the first system that can do it. “After printing, you don’t have 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. It’s a first.
This means that now, he says, “Computing units can be placed in 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 these fiber batteries could be ready for use in commercial products within a few years.
“The shape flexibility of the new battery cell allows for designs and applications that were not possible before,” says Martin Winter, professor of physical chemistry at the University of Münster in Germany, who was not involved in this work. Calling the work “very creative,” he adds, “As most academic work on batteries now examines grid storage and electric vehicles, this is a wonderful deviation from the mainstream. “
The research was funded by the National Science Foundation’s MIT MRSEC program, the U.S. Army Research Laboratory through the Institute for Soldier Nanotechnologies, the National Graduate Research Fellowship program Science Foundation and the National Research Foundation of Korea.