Packaging power

The demand for portable electricity is abundant. From mobile phones to music players, we are used to having power everywhere we go. This need is largely met at present by the use of the many different types of available batteries. Batteries have changed quite a bit in recent years from being disposable off-the-shelf items to the modern, integrated, rechargeable lithium ion batteries we know today. Though both are popular, neither is ideal for designers that have to package vast amounts of hardware around them. The need to incorporate either disposable or integrated batteries within an electronic device places limitations on the design. Despite improving massively over the last ten years, most mobile phones for example – if you can open them up and get to it that is – have a proportionally large square block taking up a considerable part of the overall housing in the phone. With the trend of manufacturers using ever thinner devices as the main metre of their technical prowess, it places a significant constraint on design possibilities. The Challenge The challenge this month is therefore to come up with a better way of packaging the power storage/supply of mobile electronic devices. It is not so much a case of trying to downsize batteries, or increase their performance, but more one of allowing them to be packaged more easily and flexibly inside electronic devices. Alternative chemistries could potentially yield greater power storage potential, but this is a massive area of global research being driven by some of the world's largest automotive and chemical companies... so we can hardly expect Eureka readers to solve this one on their coffee break. Or, can we? An alternative could be some kind of mechanism operated by winding or pulling a string. There is also a lot of talk at the moment about the possibilities of harvesting energy from the body in some way. But to get the necessary power density using these techniques – at present at least – is going to be tough. The solution we have in mind acts the same as a traditional battery but with significantly more 'bendability' and can be shaped to produce almost any shape both during and after manufacture with almost no loss in discharge performance. Removing the limitation of rigidity could open up entire new markets and possibilities to electronic device designers. The solution is fairly simple and rather elegant. When you see it you may consider it obvious. In the meantime, see if you can come up with a solution. -Solution- Solution to October 2012 Coffee Time Challenge The solution to October's Coffee Time Challenge of how to make a flexible battery comes from Korean based LG Chem. Its researchers are trying a completely new approach to develop a battery that is highly scalable, can be manufactured with a wide range of capacities, and is also extremely bendy—so much so that it could be adapted to fit nearly anywhere, freeing designers from the burden of relatively big batteries. The team coated copper wires with nickel-tin, coiled them around a rod and stretched them, obtaining a hollow spiral, spring-like flexible anode. Finally, the anode was coupled with a lithium-ion cell. The elegance of this design is that the electrolyte can be easily injected in the battery and is easily spread throughout the electrodes. Also, more importantly, battery capacity can be simply designed by controlling the number of copper wires and the thickness of the cathode composite that wraps around them. Preliminary tests showed the cable battery to be stable in discharge performance regardless of their degree of bending, with almost no change compared to a non-bending state. There was however some loss in capacity, which hasn't been characterised in detail just yet. The batteries can be woven in series or in parallel to assume nearly any shape (including sheets) with finely controlled energy density. As such, they are versatile like no other battery. LG seems to be betting on this technology, and said that if it can resolve outstanding issues (mainly capacity loss and a more thorough investigation on safety), the batteries could soon hit the market and have an enormous impact on portable, wearable, and flexible electronics in the near future. www.lgchem.com