Battery life is the scourge of every gadget owner. No matter how pretty your shiny new toy is, you'll almost certainly spend half your waking hours fretting about when it's going to die. Thankfully, scientists across the world are working to solve this incredible first-world problem -- and here are the solutions they've come up with so far.
Before looking at the future, it's worth understanding where we are with battery technology at the moment. (For the purposes of this article, we'll be looking primarily at rechargeable batteries, as found in everything from phones to cars, rather than AAAs or the like.)
The most common type of battery, by far, is the rechargeable lithium-ion cell. You'll be familiar with this from smartphones, tablets, laptops, electric vehicles, and even aeroplanes.
Lithium-ion cells are great, compared to what came before them. They have a high energy density (the amount of energy that can be stored per kilogram of battery), no memory effect, and also a low self-discharge rate (an unused lithium-ion battery will only lose around 5 per cent of its charge per month, versus 20 per cent for nickel-based batteries).
However, they're far from perfect. Lithium-ion batteries are volatile, and known for occasionally bursting into flames. More annoyingly, they degrade quite quickly, and can become totally unusable within two or three years of manufacture. Moreover, despite their high energy capacity, we're still struggling to get more than a day's use out of smartphones. So, what's the solution?
The simplest solution would be to upgrade lithium-ion batteries. One of the current limitations of current lithium-ion batteries is that they use an anode made of graphite to store electrons during the charging cycle. Although graphite is effective for this job, it's also relatively bulky.
A suggested replacement material is silicon, which, by being much smaller, would allow the energy density of lithium-ion batteries to be increased several times over. There's a problem, however: during the charging cycle, as the silicon layer absorbs ions, it physically expands and contracts, which leads to a few fairly obvious problems.
All's not lost, though -- new research from the University of Maryland has experimented with using silicon beads on a carbon nanotube, allowing the beads to expand "like balloons", and avoiding the potentially disastrous outcome of using sheets of silicon.
Another potential alternative are 'metal-air' batteries. Rather than reacting with a liquid, as in a conventional battery, metal-air batteries react metal electrodes (such as lithium, sodium or even zinc) with the oxygen in the air to produce a current.
Metal-air batteries are promising because of the potential to reduce the weight, and thus increase the energy density, of traditional batteries. Although the idea sounds a little far-fetched, it's not -- zinc-air batteries are already commonplace in hearing aids, and IBM is leading the charge in researching lithium-air and sodium-air batteries, with the aim of producing an all-electric car with a range of 1000 miles.
One of the most vaunted materials in all of science at the moment is graphene -- a layer of carbon about an atom thick. Graphene's potential doesn't lie in being a traditional battery, where an electrical current is produced through a chemical reaction. Rather, graphene has huge potential as a supercapacitor -- a material that simply stores energy.
Capacitors have an advantage over traditional batteries, as they're simple, safe, and can potentially recharge in a matter of seconds. However, the capacitors that we can manufacture now have an energy density far lower than that of batteries, making them impractical for powering stuff like phones.
Graphene could potentially change that. Researchers from Monash University have managed to create a graphene supercapacitor with an energy about half that of lithium-ion batteries -- which doesn't sound like much of an advancement, but if the capacitor can be charged in a matter of seconds, the proposition is quite different.
Probably the best-known alternative to batteries is the famed hydrogen fuel cell. Hydrogen cells work by reacting hydrogen gas with oxygen (normally from the air), which pumps ions across two electrodes, and generates electricity in the process.
Although hydrogen fuel cells are more normally thought of for powering vehicles like cars and buses, a minaturised cell would make sense for electronics. With a high energy density and very quick recharging time, the only real downside is the storage of hydrogen, which is a highly volatile (and explosive) gas.
In fact, Apple already has a patent (but of course they do) for hydrogen-fuel-cell-powered smartphones and tablets. And if you can't wait, you can already buy a hydrogen fuel cell charger to juice up your gadgetry on the move.
The final technology worth looking into is wireless charging. No, I don't mean the sort you can find in some smartphones today, which requires the device to be an inch from a giant charging coil. Rather, it's the sort of wireless charging that can power devices from significant distances away, while wandering around, that's most interesting.
The concept of wireless power isn't exactly new -- Tesla, the father of the alternating-current power system that's ubiquitous worldwide today, demonstrated wirelessly-powered lightbulbs back at the turn of the century, and even once proposed a worldwide system of wireless electricity.
Although we haven't quite achieved Tesla's dream yet, wireless power isn't a pipe dream. One Silicon Valley startup, Ossia, has recently demonstrated a technology that uses Wi-Fi spectrum to wirelessly deliver power up to a range of about 35 feet.
Although it's not a perfect system quite yet -- 90 per cent of the energy is lost in transfer, and the maximum deliverable at the moment is about 1 watt, just enough to power an iPhone -- the promise of being able to wirelessly charge your electronics while wandering around is powerful, and could almost completely remove the need for batteries in the future.