While our smartphones have grown ever more advanced and power-hungry over the last few years, improvements to their batteries have so far failed to keep pace. Now, scientists at Stanford University have developed a new battery technology that they believe might just change that.
Aluminium instead of lithium
Scientists have been looking at ways to improve battery life for some time. Last year, Stanford was experimenting with a 'pure' lithium battery as a possible way to boost battery capability. Now researchers at the university have come up with a new alternative: an ultrafast rechargeable aluminium-ion battery.
Aluminium has long been an attractive material for batteries, according to the university, thanks to its "low cost, low flammability, and high-charge storage capacity".
For decades, researchers have tried unsuccessfully to develop a commercially viable aluminium-ion battery, but "a key challenge has been finding materials capable of producing sufficient voltage after repeated cycles of charging and discharging", Hongjie Dai, a professor of chemistry at Stanford, said.
An aluminium-ion battery consists of two electrodes: a negatively charged anode made of aluminium and a positively charged cathode.
"People have tried different kinds of materials for the cathode," Dai said, but the researchers "accidentally" discovered a simple solution with graphite. The Stanford team identified a few types of graphite material that could work well, and created a system using an aluminium anode, graphite cathode, and ionic liquid electrolyte - a salt that's liquid at room temperature - inside a polymer-coated pouch.
The Stanford system has a couple of advantages on the tradtional setup. Unlike lithium-ion batteries, aluminium batteries are safe and are not a fire hazard. It's also "ultra-fast charging", according to the researchers, and in tests showed "unprecedented charging times". However, details of the charging times have not been released.
Perhaps one of the biggest claimed breakthroughs is in recharging. Aluminium batteries developed at other laboratories usually died after just 100 charge-discharge cycles. But the battery developed at Stanford "was able to withstand more than 7,500 cycles without any loss of capacity", according to the university.
Although the technology shows promise, it's unlikely to be featuring in our smartphones any time soon. While the researchers are still conducting their tests on the new technology, according to Dai, the battery they have developed currently produces "about half the voltage of a typical lithium battery". However, improvements in the cathode material could eventually lead to a higher voltage, the researchers believe.
The battery "has everything else you'd dream that a battery should have: inexpensive electrodes, good safety, high-speed charging, flexibility and long cycle life," Dai said.
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