Apple patents point to slimmer battery tech

•  by Paul Marks

Graphene, the wonder material whose glittering array of electrical and thermal properties won its discoverers a Nobel prize in 2010, could soon be helping Apple’s iPhones and iPads pack more power.

The company has filed a US patent application (2013/0136966) on a graphene-based heat sink for the lithium batteries and circuit boards in its tablets and smartphones.

Graphene is a form of carbon that comes in sheets one-atom thick, with its atoms arranged in a honeycomb lattice. It is 10 times better at conducting heat than graphite, which is often used as a heat sink in mobile gadgets.

But in order to adequately cool a battery, a graphite coating is typically 30 micrometres thick. That eats up space within the gadget enclosure that could be used for a bigger battery, explains inventor Ramesh Bhardwaj of Fremont, California, in Apple’s patent application.

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By coating a polypropylene battery casing with graphene, he says, the heat sink can occupy a fraction of the space of the graphite version for the same heat dissipation – allowing for a bigger, longer-lasting battery to be installed.

Graphene is also being explored as a substance for storing electricity in next-generation batteries and supercapacitors. At the University of Manchester, in the UK – where Andre Geim and Konstantin Novoselov isolated graphene in 2004 – researchers have just embarked on a £2.2 million research programme to create high-capacity energy-storage devices with the wonder material at their heart.

In another battery patent application filed this week, Apple gave still more clues that it is indeed working on a wristwatch-shaped device, as CEO Tim Cook hinted last week.

In US patent 2013/0136967 the firm describes the precision-manufacturing techniques behind making a curved battery – including how to apply pressure for sustained periods to a flexible lithium cell to create the curve, a little like an acoustic guitar maker might with a wooden panel.