Experimental lithium-ion battery can be stretched, twisted and wirelessly charged
By Ben Coxworth
February 27, 2013
Thanks to the advent of stretchable electronics, we’re currently witnessing the development of things like smart fabrics, bendable displays, and even pressure-sensitive skin for robots. In many potential applications, however, the usefulness of such electronics would be limited if they still had to be hooked up to a rigid battery. In response to that problem, a team of scientists have recently created – you guessed it – a stretchable lithium-ion battery.
The research was led by Northwestern University’s Yonggang Huang and the University of Illinois’ John A. Rogers.
The battery they created consists of 100 small, rigid electrode disks arranged in a square array, embedded within a sheet of stretchy silicone elastomer. Those electrodes are interconnected in parallel using metal wires that are each laid out like a flat spring, in the shape of a single squashed letter S. Within each of those single S’s, however, the wires in turn take the form of multiple smaller S’s joined end-to-end. Just picture a telephone cord arranged in an S shape, and you start to get the idea – the shape acts as a spring, but so does the cord from which it’s made.
When the silicone sheet is stretched and the distance between the electrodes increases, the connecting wires uncurl to bridge the gaps. The single larger S of each wire first straightens out, followed by the smaller S’s within it. All told, the battery can be stretched by up to 300 percent of its original size, while remaining functional. It also stands up well to repeated folding and twisting.
Because such batteries might end up powering medical implants or other hard-to-access devices, Huang and Rogers designed their prototype allowing for the inclusion of stretchable inductive coils – this would allow it to be charged wirelessly.
The scientists claim that their battery is similar in power and voltage to a similarly-sized conventional lithium-ion battery. It is currently able to continuously power an LED bulb for up to eight hours per charge, and can stand up to 20 recharging cycles with little loss in capacity.
A paper on the research was published yesterday in the journal Nature Communications. The battery can be seen getting stretched while still delivering power, in the video below.
Source: Northwestern University