New research pushes aluminium batteries as the next generation technology to revolutionise mobile devices, but what else could finally make smartphones last more than a day
New research by Stanford University into aluminium batteries promises to produce cells that are big enough for a smartphone and charge in just 60 seconds.
The new high-performance aluminium-ion battery is the first using the metal – more commonly found in aircraft and car bodies – to demonstrate long life and fast charging. It does this using a graphite electrode. Previous aluminium batteries have suffered from poor life, failing after 100 recharge cycles.
Stanford’s new battery can be recharged around 7,500 times. Typical lithium-ion batteries used in everything from smartphones and laptops to electric cars last around 1,000 recharge cycles.
But the new aluminium-ion batteries are far from being available for commercial use in electronics, producing just half the voltage of lithium-ion batteries.
“I see this as a new battery in its early days. It’s quite exciting,” said Ming Gong, one of the authors of the study published in Nature. “Improving the cathode material could eventually increase the voltage and energy density. Otherwise, our battery has everything else you’d dream that a battery should have: inexpensive electrodes, good safety, high-speed charging, flexibility and long cycle life.”
The new aluminium battery technology is not the only one vying to solve our battery life crunch – the primary issue holding back current electronic devices.
Nanotube-based batteries
Current lithium-ion battery technology will reach its limit soon – there is only so much that can be achieved through tweaking the battery chemistry of a lithium-ion system – but a change in the way the electrode is made, using nanotechnology, could breath new life into lithium. By making the electrodes out of nanotubes researchers have dramatically increased the rate of recharging the batteries, reaching a 70% charge in just two minutes.
Some researchers have used both silicon in place of graphite for the new electrodes. Others, including a team from the Nanyang Technology University in Singapore have patented the use of titanium dioxide nanotubes, which has been licensed for commercial development and could be available within two years.
Pros: fast charging, longer recharge life (ie the number of times it can be recharged)
Cons: similar energy density to current batteries means similar battery lifeSulphur-based batteries
Research focused on squeezing longer battery life out of the same-sized batteries has experimented with different battery chemistries. One promising candidate is the sulphur-based battery.
Lithium-sulphur batteries promise up to five times the amount of energy per gram as current lithium-ion technology. Once commercially available lithium-sulphur batteries are more likely to have an energy density closer to twice that of current batteries, but that would enable twice the battery life for devices and cars.
The technology has been in development for over 20 years, and at least one company is aiming to have lithium-sulphur batteries powering electric cars by 2016, but batteries designed for portable devices such as smartphones are likely to be many years away.
Pros: at least twice the battery life
Cons: low recharge life, volatile chemistry, similar recharge timesMetal-air batteries
Metal air batteries replace the cathode, which is typically graphite in traditional lithium-ion cells, with oxygen in the air. This saves weight and provides a cathode that can simply be replaced with fresh air that is essentially free.
Saving weight means a higher energy density, which some researchers have claimed to be similar to petrol in these batteries, meaning longer life, making it ideal for electric cars. Tesla has a patented system for integrating metal air batteries into its electric cars, while an electric Citroen C1 was driven 1,800km on a single charge using the technology.
But degradation issues, problems recharging them and poor recharge life cycles have hampered commercialisation of the technology.
Pros: very high energy density means fantastic battery life
Cons: difficult to recharge, poor recharging lifeSolid-state batteries
Solid-state batteries remove the liquid electrolyte required by most other batteries to transfer ions between electrodes and generate electricity. In doing so they have a much higher energy density.
Battery firm Sakti3, which recently saw investment and a commercial partnership with British vacuum firm Dyson, claims its batteries could store up to twice the energy and therefore battery life as current lithium-ion batteries.
Pros: twice the battery life, safer, could be made into different shapes and sizes, more environmentally friendly
Cons: not manySupercapacitors
Capacitors are used in all kinds of technology, but commonly in devices that need a lot of electricity in a very short space of time, like a flash or a sub-woofer in a car. They charge in seconds but release all that charge in one go.
A supercapacitor works in a similar manner, charging in seconds but releasing its energy more slowly, like a battery. Current research using graphene promises supercapacitors that charge in about 16 seconds and can be recharged over 10,000 times. But even the best supercapacitors can only store energy in densities about the same as current lithium-ion batteries.
Pros: almost instant charging, very long recharge life, potential for use as a secondary electricity storage device in electric cars
Cons: low energy density, therefore lower battery life
New battery technology is coming and could be in electric vehicles before the end of the decade, but it could be several years before cells fit for use in portable electronics make our smartphones last more than a day.