US engineers have found a way to make lithium batteries that are smaller, lighter, longer lasting and capable of recharging in seconds.
The researchers believe the quick-charging batteries could open up new applications, including better batteries for electric cars.
Because they use older materials in a new way, the batteries could be available for sale in two to three years, a team from Massachusetts Institute of Technology reported on Wednesday in the journal Nature.
Current rechargeable lithium batteries can store large amounts of energy, making them long-running. But they discharge energy slowly and require hours to recharge. Scientists traditionally have blamed slow-moving lithium ions — which carry charge across the battery — for this sluggishness.
However, about five years ago, Gerbrand Ceder and a team at MIT discovered that lithium-ions in traditional lithium-iron-phosphate battery material move quite quickly. "It turned out there were other limitations," Ceder said in a telephone interview.
Ceder and colleagues discovered that lithium ions travel through tunnels accessed from the surface of the material. If a lithium ion at the surface is directly in front of a tunnel entrance, it can quickly deliver a charge. But if the ion is not at the entrance, it cannot easily move there, making it less efficient at delivering a charge.
Ceder and colleagues remedied this by revamping the battery recipe. "We changed the composition of the base material and we changed the way it is made — the heat treatment," Ceder said.
This created many smooth tunnels in the material that allow the ions to slip in and out easily. "The trick was knowing what to change," he said.
Using their new processing technique, the team made a small battery that could be fully charged in 10 to 20 seconds.
Ceder thinks the material could lead to smaller, lighter batteries because less material is needed for the same result. And because they simply tinkered with a material already commonly used for batteries, it could be easily adapted for commercial use.
"If manufacturers decide they want to go down this road, they could do this in a few years," Ceder said.
One glitch, Ceder noted, would be handling the extra surge of power. "All of the wiring has to get beefed up," he said.
Talkback
If a battery can be charge very rapidly that implies a high charging current, which would require charger, cables etc. to be capable of working with that current.
What happens if such a battery is accidentally discharged by short circuit? Would it be capable or producing dangerously high currents with consequent fire risk?
I've got some 15 miniute NiMH batteries, which come with a very beefy charger that has a fan capable of floating an elephant in a tutu. They work fine: I understand (but have never checked!) that they've got current limiters and fuses built-in.
Of course, there is more danger: if you've got something capable of sucking up ten amps, it'll be capable of dumping tons of energy into some hapless short circuit through the same low impedance. However, that's been true of secondary cells for a while now. I think a bigger danger is higher energy density, because the real risk comes from creating an intense heat source over time - the more energy you can sustainably release, the higher the chances of catastrophe.