You can shrink them, make them skinny, or make them swallow more charges – but unless you're a Maker Faire type, you can’t actually wear a battery. Until now.
Engineering and chemistry boffins working with LG Chem have devised a cable-like lithium-ion battery just a few millimetres in diameter – and flexible enough to be twisted, knotted and bent. LG Chem, part of electronics giant LG, is one of the world’s largest suppliers of lithium-ion batteries.
That means, rather than putting a solid battery inside a device like laptop, iPad, phone or camera, you could wear it as part of your clothing.
The idea is to encourage more flexible personal computing and, possibly, devices that become even smaller and lighter as the battery’s living quarters are eliminated.
In a document here (PDF), the team write of their work: "Instead of mounting the battery inside the device, it could be worn on the wrist, neck, or any other part of the human body, allowing maximum freedom in the device design and a strong boost for the realization of practical wearable electronics.”
They note that with keyboards and screens becoming flexible, greater attention has been paid to polymer electronics and nanometer sized materials capable of conducting current.
The battery is conceptually rather simple. A copper cable was coated with nickel and tin to produce the anode, it was wrapped with a cathode composite and packing insulator, the cable was twisted in to create a spiral – like a spring with the core left hollow – and then the spring was coated with lithium cobalt oxide to make the cathode. An outer insulating coating was added with the electrolyte poured down the middle of the spring.
The capacity of the battery could be increased by adding more stands and making the strands thicker.
The team charged a battery to 4V and were able to power a red LED screen and an iPod shuffle. The battery was then bent, with the current it produced remaining at a constant level.
“Compared with other recent film-type flexible batteries the variation in the discharge characteristics of our battery is quite negligible, strongly indicating that our cable battery will exhibit mechanical robustness in real operating environments,” the boffins said.
They note more testing is needed, especially on safety and standards not least given the sheer prevalence of lithium-ion batteries and their propensity to explode or catch fire.
Brings a whole new meaning to "hot pants". ®
The paper was written by researchers at South Korea's Pusan National University, Kangwon National University, Chungnam National University and the Ulsan National Institute of Science & Technology (UNIST), together with researchers from from the battery R&D division at LG Chem, also in South Korea, and published in Advanced Materials.