LG Chem, a member of the LG conglomerate/chaebol and one of the largest chemical companies in the world, has devised a cable-type lithium-ion battery that’s just a few millimeters in diameter, and is flexible enough to be tied in knots, worn as a bracelet, or woven into textiles.

The underlying chemistry of the cable-type battery is the same as the lithium-ion battery in your smartphone or laptop — there’s an anode, a lithium cobalt oxide (LCO) cathode, an electrolyte — but instead of being laminated together in layers, they’re twisted into a hollow, flexible, spring-like helix.

LG Chem’s battery starts with thin strands of copper wire, which are coated with a nickel-tin (Ni-Sn) alloy to create the anode. These strands are twisted into a yarn, and then wrapped tightly around a 1.5mm-diameter rod. The rod is removed, leaving a strong spring. Next, aluminium wire is wrapped around the spring, and then the whole caboodle is dragged through a slurry of lithium cobalt oxide, which coats the aluminium wire and becomes the cathode. Finally, the anode-cathode spring is wrapped in a protective outer coating, and then an electrolyte is poured down the middle of the hollow spring to create a battery.

Now, flexible batteries have been created before — but they’ve all just standard, flat, laminated batteries made from sub-optimum materials, such as polymers. As such, as they have very low energy density, and they’re only bendy in the same way that a thin sheet of plastic is bendy (see video below). LG Chem’s cable-type batteries have the same voltage and energy density as your smartphone battery — but they’re thin and highly flexible to boot. LG Chem has already powered an iPod Shuffle for 10 hours using a knotted 25cm length of cable-type battery. LG’s goal is to have this battery ready for mass production by 2017.

If you aren’t already aware, batteries are the single biggest limitation when it come to the continued proliferation of high-power ubiquitous computing. While Intel is forging ahead with transistors that are just a few atoms wide and processors that can perform billions of operations per second while consuming just a couple of watts, we are still stuck with clunky batteries that can only be formed into a handful of shapes.

If you removed batteries from the equation, new form factors would explode onto the market. Instead of cylindrical batteries in laptops, or pouch-shaped batteries in smartphones and tablets, cable-type batteries would let you put batteries everywhere — around the outer edge of the chassis, around the screen’s bezel. Instead of creating devices with integrated batteries, you could instead wear a battery around your neck, or waist, or otherwise integrated into your clothing — and then plug into the device. Smartphones and tablets would instantly lose half their weight, and devices with flexible, roll-uppable displays would suddenly become feasible.

Research paper: DOI: 10.1002/adma.201202196 (paywalled)