How a self-healing battery could mean more life for your phone

Ready for a smartphone battery that lasts longer? Scientists have found a way to seal up the cracks that occur over time lithium ion batteries, making them last longer. 

Brad Plummer/SLAC National Accelerator Laboratory
(From left to right): Dr. Zhenan Bao, post-doctoral student Chao Wang, and Dr. Yi Cui were among the team of researchers that worked on developing the self-healing polymer that Wang is holding.

A self-healing silicon electrode could mean a longer battery life for your smartphone, laptop, or electric car. 

Researchers from Stanford University and the SLAC National Accelerator Laboratory have created a battery electrode that heals itself. This could mean a longer life for the lithium-ion batteries used in iPhones and other devices.

Most lithium ion batteries use carbon electrodes on their positive site, which is called an anode. But silicon electrodes can store 10 times more lithium, says Yi Cui, an associate professor at Stanford and one of the lead researchers. This means a longer battery life.

So then why don't most batteries use silicon electrodes? 

Because the tiny particles they're made of swell to three times their size and then shrink again during each charge cycle, the team wrote in their paper. This causes them to eventually crack and fall apart.

"If you can make silicon work to replace carbon, there's a huge impact right there to store a lot more energy," Dr. Cui says. 

The team solved the problem with a synthetic polymer goo that heals the cracks within hours. Electrodes coated with the mixture lasted 10 times longer. 

"I think this is really a promising approach to make silicon workable for the battery electrode," says Cui. 

The team got the idea while another group, headed by Stanford professor Zhenan Bao, was working on developing artificial electronic skin

"We were thinking, 'Why can't we combine a self-healing polymer together with a battery?'" says Cui. "That's how we started this project."

The hydrogen-bond formation within the polymer works like a zipper to zip up the cracks, explains Cui. To keep the mixture electrically conductive, the team also added carbon nanoparticles. 

Cui, Bao, and others actually already created a silicon anode earlier in the year using nanoparticles – even smaller than the microparticles used in this research. 

The nanoparticles are so small that there is no risk of them breaking down any further, Cui says. The trick here was keeping up an electrical connection between the tiny particles using a hydrogel.

But Cui says micro-size silicon particles are a lot cheaper and easier to make. 

"If you can make micro-size particles work, then you can have a very big impact," Cui says. "In the past, making microsize particles work was much harder because they would break. Nano-size particles don't break."

The team still wants to work on improving the number of charge-discharge cycles the electrode can endure before losing its permanent storage ability. It's a process all batteries go through before they begin to die. 

What's a charging cycle? Apple defines one cycle as going through 100% of the battery and charging it back to full. Once an iPhone or iPod goes through a certain number of these charge cycles, the device will lose its original battery capacity. At that point, your iPhone will charge only to 80 percent of battery life.

The electrodes worked at full capacity for 100 charging cycles – cell phones and laptops typically go through 500 cycles before deteriorating, Cui says. Electric cars typically go through 3,000 cycles. 

In contrast, the nanoparticle silicon anodes could go through a full 5,000 cycles. 

"So far our performance of using self-healing for microsize particles still needs improvement to get to the same level as the nanoparticle performance," Cui says. "At least this study..really shows that this self-healing concept is very promising."

You've read  of  free articles. Subscribe to continue.

Dear Reader,

About a year ago, I happened upon this statement about the Monitor in the Harvard Business Review – under the charming heading of “do things that don’t interest you”:

“Many things that end up” being meaningful, writes social scientist Joseph Grenny, “have come from conference workshops, articles, or online videos that began as a chore and ended with an insight. My work in Kenya, for example, was heavily influenced by a Christian Science Monitor article I had forced myself to read 10 years earlier. Sometimes, we call things ‘boring’ simply because they lie outside the box we are currently in.”

If you were to come up with a punchline to a joke about the Monitor, that would probably be it. We’re seen as being global, fair, insightful, and perhaps a bit too earnest. We’re the bran muffin of journalism.

But you know what? We change lives. And I’m going to argue that we change lives precisely because we force open that too-small box that most human beings think they live in.

The Monitor is a peculiar little publication that’s hard for the world to figure out. We’re run by a church, but we’re not only for church members and we’re not about converting people. We’re known as being fair even as the world becomes as polarized as at any time since the newspaper’s founding in 1908.

We have a mission beyond circulation, we want to bridge divides. We’re about kicking down the door of thought everywhere and saying, “You are bigger and more capable than you realize. And we can prove it.”

If you’re looking for bran muffin journalism, you can subscribe to the Monitor for $15. You’ll get the Monitor Weekly magazine, the Monitor Daily email, and unlimited access to CSMonitor.com.