Batteries are one of the limiting factors in today's mobile gadgets. However, the recent discovery of a graphene 'super-capacitor' could pave the way for impossibly thin, flexible batteries that charge in 20 seconds and last all day.
Over the past few years we've all become increasingly reliant on mobile technology. The power of modern smartphones and tablets are such that they can replace many of the tasks that had previously been the preserve of traditional PCs, while being small enough to fit in our pocket.
They’ve revolutionised the way we work, communicate, and play Pictionary-style games across a worldwide network. But this new found freedom presents a problem that has become somewhat of an obsession with manufacturers : how do you make these gadgets last longer between recharges?
Look inside many of the top smartphones and you’ll see that a sizable proportion of the internal space is packed with as much lithium-ion as the case will hold. The number of hours that a smartphone, tablet or laptop can run on a single charge is now listed with pride among the technical specs.
For example, at the recent Apple keynote the crowd (or at least the first few rows of Cupertino faithfuls) gasped and cheered when Phil Schiller announced that the new MacBook Airs had effectively doubled their battery life. This makes sense of course, because the longer something lasts the more you can get done. It also spares us the potential social embarrassment of soliciting strangers in coffee shops who happen to be sitting next to the only available power socket.
It isn’t just longevity that poses a challenge at the moment. There’s also the issue of size, and flexibility. The slab like nature of our phones makes them practical when typing or navigating a hero away from the onrushing clutches of Temple caretakers. This advantage ends the moment we forget that the device is in our back pocket and sit down. Then, while the deft hands of nurses wield their tweezers with skill, we’re left wondering what life would be like if our technology could bend?
Wearable devices are the next big thing on the horizon, and the types of inventions being imagined are incredible. To work well though they’ll need to blend seamlessly with our clothes, which means no battery packs stabbing into our ribs or flapping about as we briskly pursue happiness. That’s before you even consider the aesthetic issues of bulging, warm areas about our person. With these challenges in mind manufacturers are turning to the new wonder material of the digital age, one that could have a profound effect on how we design and power devices in the future: welcome to the world of graphene.
What is graphene?
‘Graphene is a single layer of carbon,’ explains Dr Richard Kaner, Professor of Chemistry and Biochemistry at UCLA. ‘It’s one of the strongest materials ever known, and it’s completely flexible.’
Make no mistake, Graphene is high-end science. In fact, the Manchester University academics Andre Geim and Konstantin Novoselov who successfully isolated the material in 2005, both received the Nobel Prize for their efforts. The method of production they devised - taking graphite and peeling it with sticky tape - seems a little bit like a make-and-do session at a primary school, though.
It also precludes any kind of mass production, so researchers like Dr Kaner have been exploring other ways of creating the valuable substance. Oddly enough, the one they came up with still feels somewhat home-brew for such an advanced area of study.
‘We start with graphite oxide,’ Kaner continues, ‘which is a water dispersible material. We then coat it onto sheets of plastic, we hit it with light from a laser...[it] deoxygenates and turns it into graphene.’
This might sound like something conducted in the depths of a super high-tech lab, but the laser is nothing more than a standard, consumer grade DVD writer, and the plastic sheets are fed into it as you would a normal CD or DVD. When they come out, the graphene is peeled away from the DVD surface to reveal a thin, durable, film.
‘The real exciting discovery,’ Kaner reveals, ‘was when Maher [scientist at UCLA] dragged me into the lab. He said ‘take a look at this’ and he took a lightbulb and just turned it on with this little piece of graphene. But the amazing thing is that it doesn’t stop working. After charging this sheet for two or three seconds he ran this light for over five minutes. I thought we had something very important. I thought the world had changed at that moment’.
Graphene: a super-capacitor
What Kaner and Maher had discovered was that graphene has the ability to be a supercapacitor. Traditionally, batteries are able to hold large amounts of charge that they release slowly, but this also means that they recharge slowly. Anyone who realises just before leaving for work that they’ve forgotten to charge up their smartphone overnight will attest to that.
Capacitors charge much quicker, but they can only hold small amounts of power, so they wouldn’t last long in the demanding world of power-hungry 5in smartphone screens. A supercapacitor, as the name suggest, retains the rapid charge times but increases the amount of storage available: the holy grail of batteries, if you will.
The upshot of this is that you could plug in your tablet, laptop, or phone for only a couple of minutes and it will be completely charged and ready to go by the time you’ve put on your coat and shoes.
That's amazing enough, but the fact that graphene is so thin means devices can be made thinner. If you thought the iPhone 5 was thin, just wait until graphene-powered smartphones emerge.
Yet another benefit to this 'miracle' material is its flexibility. This, along with the big power reserves, makes it perfect for wearable gadgets. The smart watches and activity trackers of the future will make the Nike Fuelband look positively chunky and archaic.
Graphene: enhancing existing battery tech
Alongside the ability to charge quickly and last for hours, graphene also provides scientists with an opportunity to address the other problem that traditional batteries exhibit, mainly that of reduced capacity over time.
At a basic level, a battery has an anode at one end and a cathode at the other. In the middle is an electrolyte which allows the electric charge to flow between the two points. When one of these elements begins to degrade, the battery itself loses the ability to retain a charge.
‘That is the problem with these high-capacity anode materials like tin and silicon,’ explains Dr Gordon Graff, from the Pacific Northwest National Laboratory (PNNL). ‘We know they have tremendous capacity...they have terrible cycle life. On repeated charge and discharge they will always tear themselves apart. Essentially tear their structure apart.’
PNNL has been researching ways to improve batteries in response to the US Department of Energy’s desire to convert its transportation fleet to electric powered vehicles. The method they discovered was one was where the previously destructive tin oxide anode material was placed between graphene sheets.
‘The graphene sheets function as a good conducting material to connect the electrons in the battery.’ says Dr Jun Liu from PNNL, ‘At the same time, when you charge/discharge the electrode material the tin oxide will expand and shrink. However because they are sandwiched between the graphene sheets, the whole material doesn’t fall apart. Therefore you retain the good stability’.
The conductive and transparent nature of graphene also lends itself to the production of displays, something that phone manufacturers are beginning to see as a real possibility. Prototypes of flexible graphene screens have already been created by Samsung in its Sungkyunkwan University, and you can be sure that other companies are investing heavily in this technology.
The British government has even allocated £21.5 million to various UK universities involved in graphene research, which has been matched by industrial partners such as Rolls Royce, BAE Systems, and Dyson. The stage is now seems set for the graphene revolution to take place, but like most miracle materials that grab the headlines, the actual realisation of these dreams may be a little way off yet.
‘When you make a discovery...you’ve got to be patient’ stated Dr Neil Alford, of Imperial College London, in a recent interview with Channel 4 News. ‘Generally from invention to commercialisation takes anywhere between ten, fifteen, twenty years. In this case I think that there are a number of aspects to graphene that make it amenable to rather earlier commercialisation. I think the flat-screen displays for example, we might see some aspects of that moving in rather sooner, maybe the three to five year timeframe.’
While you might not be rolling up your Samsung Galaxy S6 or charging an iPhone 7 in under five minutes, the models that follow soon after them may well offer these features as standard.
Just as the idea of rewinding a film after you’ve watched it seems alien and archaic to a generation raised on DVRs and DVDs, overnight battery charging or cracked screens could well become another curiosity in the museums of the tomorrow.