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The ageing, tiring Li-on in the machine

Friday, 2 November, 2012

Apple’s iPad Mini goes on sale today and lots of early-bird geeks are busily tearing down the device in one of those weird rituals that has become associated with product launches. Regardless of the hype about how magical these products are, however, all portable electronic devices have a battery and batteries do wear out over time, which means that they have to be replaced. As a result, Apple’s $99 battery replacement program is outrageously expensive relative to the $329 price.

Communal charging in New York Here’s another thing about batteries: They need to be charged. “If you plan on coming into Manhattan, bring cash, a phone charger, and cigarettes,” tweeted Vito Ferraro. “You will automatically be Mayor. #NYC #Sandy”. The image here that Greg Clayman tweeted with the caption ” Public phone charging on 40th St — just outside the dead zone” speaks volumes about the vulnerability at the core of the machine.

Sure, the latest iPads come with a 24.8-watt lithium-ion (Li-ion) polymer battery that Apple claims can carry the user through 10 hours of surfing, but Moore’s Law doesn’t apply to batteries and since the first Li-ion batteries appeared in 1991, the transistor count in the information devices they power has increased a thousand-fold while the batteries have just managed a mere 3x increase in their volumetric energy density in over the same time.

Jargon note: Energy density determines the amount of run-time you can pack into a given size (volumetric) or weight (gravimetric) of a battery.

Backgrounder: In the late 1970s, Professor M. Stanley Whittingham of Binghamton University in New York conducted a series of battery experiments using lithium as a pole in one instance. He discovered he had a powerful energy source, but it came at a price. Lithium is highly combustible and reacts explosively to water. Not exactly the kind of thing you would want to keep close to your ear on a rainy day, in other words. Batteries made with lithium-ion materials turned out to be safer and offered all the merits of lithium without the perils.

But now we’ve reached the point where changes in the battery chemistry are needed, urgently. And just in our hour of need along comes Li-imide, which doesn’t generate hydrofluoric acid and so delivers a huge improvement in thermal stability and battery life. It also permits thinner batteries by eliminating most of the puffiness characteristic of current Li-ion pouch cells over their working life, which forces device designers to sacrifice space to accommodate the swelling. So, hang in there, New Yorkers, help is on the way. Mayor Bloomberg might prefer to distract you with visions of climate change, but it’s Leyden Energy that will put an end to your charging nightmare.


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