5 more tech breakthroughs: Innovations in access, power and control

Self-healing batteries: Just-in-time repair

We all know the drill: You use your mobile device -- phone, tablet, laptop -- for a few years, then the battery dies and you have to replace it. Or you drop the device, the battery shorts out and you have to replace it even sooner.

And if a device isn't designed to allow the user to replace the battery himself (iPhones and iPads and other tablets are notorious for this), there's the extra hassle and expense of shipping the whole thing back to the manufacturer to swap out the battery.

But scientists at the Beckman Institute for Advanced Science and Technology at the University of Illinois at Urbana-Champaign have a better idea. Researchers led by professor Scott White are looking to extend the useful life of batteries in mobile devices, and they've figured out a way for the battery to fix itself, probably without the user ever knowing there was a problem.

Whether it's in a mobile phone or a notebook, a lithium-ion battery releases electricity by moving electrons from the lithium-based cathode to the cell's anode. The flow is reversed when you plug the device into a power source to charge the cells up for another cycle.

The problem is that over time, or if the battery is subject to a sudden shock, the battery's cells can be damaged, resulting in a power-killing short. At this point, all you can do is get a new battery.

White's team has tackled this problem by coating the battery's cathode with billions of microspheres filled with gooey gallium-indium. The key is that the spheres have been designed to break open when stressed (like when the device is dropped) or heated up (as when the battery shorts).

"We can trigger the microcapsules through mechanical force, temperature or pH," explains White from his lab at the university. "The capsules release their contents when damage occurs and a healing reaction takes place."

The gallium-indium quickly can flow in to fill in the gaps to fix the short, and the battery can be restored in as little as 40 microseconds. In most cases, that's not even enough time for the battery's control electronics to shut it down. "We get restoration of conductivity," adds White. "It is immediate."

For now, the microcapsule method works just once; if you drop your device a second time, you're out of luck. But White told me his team is working on ways to incorporate several different materials to make it possible to fix a battery several times.

The typical notebook battery gets about 100 to 150 charge cycles per year and lasts about three years before degrading to the point where it needs to be replaced. Using the Beckman Institute's techniques, five or six years is doable, and eventually we might see a 10-year computer battery.

"This is kind of cool, and very needed today," says Stanley Williams, senior researcher and head of the Quantum Science Research (QSR) group at HP Labs. "Batteries are the weak link in many of the products we use every day."

When might a self-healing battery be available? White, who was preparing a paper on the topic when we launched this story, is cautious, saying that the microcapsule method is still in the lab. Still, he says that adding microcapsules to a battery shouldn't interfere with the way they are made and shouldn't add too much to the cost of a cell.

Long term, he adds, the process could be used to fix all sorts of electronics, even an electric car's battery, effectively repairing it before we even know it's broken. Next on White's list are the power transformers and capacitors that make our electrical power grid work. If his group succeeds, someday we could conceivably see an end to power failures.