In what can be termed a breakthrough in wearable battery technology, researchers at MIT have developed the world's longest flexible battery, a rechargeable lithium-ion unit in the form of an ultra-long fiber. Just how long is it? It's a staggering 460 feet (140 meters), and it could eventually stretch much, much farther.
Published in the journal Materials Today, the length of the battery was a proof of concept that the material can be manufactured to arbitrarily long lengths.
The battery was fabricated for the first time using a thermal drawing method, and it could be used to make 3D-printed batteries in any shape. According to the team, the Li-ion fiber battery also opens up a myriad of opportunities 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.
Though researchers have previously created fibers that contain a wide variety of electronic components, they relied on an external power source. Now, this fiber battery, which is weavable and washable like its predecessors, could enable such devices to be completely self-contained.
In previous reporting, we noted that lithium might be the future of battery technology, and it seems that assertion may have just been proven true.
A step ahead
The new fiber battery is manufactured using novel battery gels and a standard fiber-drawing system. In a press release issued by MIT, MIT postdoc Tural Khudiyev noted that previous attempts to make batteries in fiber form were structured with key materials on the outside of the fiber. In the latest development, his system embeds the lithium and other materials inside the fiber, with a protective outside coating, creating a stable and waterproof version. He said it demonstrates that it's possible to make a fiber battery that can be up to a kilometer long and highly durable, having many practical applications. As Khudiyev puts it, "there’s no obvious upper limit to the length. We could definitely do a kilometer-scale length."
The 140-meter fiber produced can charge smartwatches or phones, with an energy storage capacity of 123 milliamp-hours.
“The beauty of our approach is that we can embed multiple devices in an individual fiber," said former MIT postdoc Jung Tae Lee. The team had exhibited the integration of LED and Li-ion batteries in a single fiber, and Lee 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 reaggregate of a compact fabric computer," he added.
3D and ready for use within a few years
The material can also be used in 3D printing or custom-shape systems to create solid objects. To demonstrate this, a toy submarine was wrapped with the fiber to provide it with power.
“This is the first 3D printing of a fiber battery device,” said Khudiyev. He continued by noting that, if you want to make complex objects through 3D printing that incorporate a battery device, 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," he said.
The research team has applied for a patent on the process and continues to make progress in power capacity and variations on materials.
Ultimately, this is just the latest development in novel battery technologies. Earlier this year, a team of researchers in Singapore created a "paper battery" roughly the thickness of two strands of human hair. Similarly, Stanford scientists developed a new flexible, lightweight solar panel material that they believe could power wearables, electric vehicles, and even light spacecraft.