Researchers at the Massachusetts Institute of Technology 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.
Unlike other approaches which need integration of multiple fiber devices, the MIT method embeds multiple devices in an individual fiber. The new fiber battery uses 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.
As a proof of concept, the team produced a 140-meter fiber with an energy storage capacity of 123 milliamp-hours—enough to charge smartwatches or phones. The fiber is only a few hundred microns in thickness.
The fiber 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 (pictured) 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.