The power behind the next mobile revolution

By John Leonard
17 Feb 2014 View Comments

A significant technological advance that took place in 1991, without which it is doubtful the mobile revolution would have ever taken off. That advance was the commercial release of the first lithium-ion (Li-ion) battery by Sony.

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“Game changing battery technologies do not come around very often,” said Paul Blackmore, project consultant at Warwick Manufacturing Group’s Energy Innovation Centre at the University of Warwick.

While processors, memory and storage continue to pack more performance into smaller units in line with Moore’s Law, he said, battery miniaturisation is a much slower process.

“The increase in battery energy density [energy stored per unit volume] for a given chemistry follows a law of diminishing returns. That is until someone invents a battery system with a step change in performance, which was the case with the Li-ion battery.”

Modern mobile devices and apps continue to add new energy sapping features with every iteration. But for the last few years the battery has been the slow fat kid in the team hurdles race, the one that lets the whole side down.

“Hardware designers are always looking to decrease power usage. They put a lot of effort and development work into it. They come to battery makers and say: ‘Hey we’ve done this, what are you going to do?’,” said John Lettow, CEO of US battery manufacturer Vorbeck.

The ideal battery would be very small and light, cheap to manufacture from non-toxic abundant materials, quick to charge with a large capacity, provide power over a long lifetime without degrading or becoming too hot, and easily recycled at end of life.

Unfortunately though, enhancing one parameter tends to have an adverse effect on another. For example, capacity and energy density are inversely related as are size and heat generated: make a battery smaller and it tends to run hotter and require charging more often.

For mobile technologies, and especially in the emerging area of wearable computers, size and weight are obviously vital statistics but there are many others too, such as flexibility, and – not least – safety.

“Safety would be at the top of any list, and with high-energy density batteries this needs careful consideration,” said Professor Ben Allen of the Centre for Wireless Research at the University of Bedfordshire.

Many of the materials used in battery construction are flammable or toxic, and, in the case of a short circuit or if the cell is overcharged or overheats, can potentially ignite, a problem that increases as sizes decrease.

“We need to think outside the brick,” said Lettow, explaining that batteries are now being made in flexible pouches that can fit inside the shoulder strap of a bag.

“To take a new technology into the marketplace you need to produce a real jump in performance.”

Lithium lasts a long time

While many researchers are trying to knock Li-ion off the perch it has sat on for so long, the consensus is that we will see improvements around that technology before we see another big change.

“I really think the lithium battery will continue to play a very strong role in mobile computing, reasons being the availability of manufacturing facilities, weight to capacity ratio as well as the compactness of the battery,” said David Jazani, senior lecturer and link tutor at the University of Bedfordshire.

However, the step change may come through technologies being developed for other applications, such as electric vehicles.

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