Science & Technology

Scientists Have Developed a Self-Repairing Battery

If you've ever owned the same smartphone or laptop for several years, you've likely noticed that at some point, the battery couldn't hold a charge quite as well as it did when it was new. Scientists have noticed that, too, which is why a major area of research involves extending the lifespan of batteries. Last month, scientists announced that they may have achieved a breakthrough: They figured out how to give batteries self-repairing powers. That means higher capacities and longer lives — maybe even for the battery in a device you'll own someday.

The Fault in Our Bars

Whether it's your garden-variety AA copper-top or the rechargeable powering your electric car, all batteries contain the same basic components: a positive electrode (which on AA batteries corresponds with the + end), a negative electrode (the - end), and an electrolyte between them. Rechargeable batteries, like the lithium-ion battery in your smartphone, charge via a chemical reaction that makes charged particles, or ions, travel from the positive electrode through the electrolyte and into the negative electrode. When it's time to produce power, the ions travel back from whence they came, from the negative electrode back through the electrolyte and into the positive electrode.

Self-repairing batteries would have longer lifetimes than batteries at present.

The electrodes in a rechargeable battery are generally made up of many atom-thick layers of some type of metal. In a lithium-ion battery, the negative electrode is made of graphene (basically, sheets of carbon atoms), and the positive electrode is made of lithium cobalt oxide or lithium iron phosphate. These layers are held together via the weak Van der Waals force, which is the force that exists between very closely packed neutral particles (and the same one that helps spiders crawl on the ceiling).

When the battery is charging, the lithium cobalt oxide in the positive electrode releases some of its lithium ions to pass through the electrolyte and hang out between the layers of graphene in the negative electrode. That release of ions physically changes the electrode, creating a little bit of extra space between the layers. Since the forces holding the material together rely on the atoms being closely packed, that extra space threatens to degrade the electrode and will eventually lead to cracks or flakes known as stacking faults. Over time, these stacking faults reduce the battery's ability to store and deliver a charge. If scientists figure out a way to prevent or repair these cracks, they may end up creating a significantly longer-lasting battery.

Opposites Attract

In a paper published in Nature last month, engineers at the University of Tokyo announced that they'd developed a way to make batteries repair these cracks on their own. Instead of lithium ions, the team used sodium, which is a promising alternative that we've written about before.

By building the electrode layers out of a material that has an extra sodium atom, they made the natural degradation of the layers reversible. One reason for that is the material they used was held together by a force called coulombic attraction, which is the fancy term for the attraction between particles with opposite charges. It might not sound all that impressive, but the force of coulombic attraction is much stronger than Van Der Waals forces, which means that the new material they made the electrode out of is capable of a lot more than your run-of-the-mill electrode. Thanks to this more powerful force, once the sodium ions make their way back to the positive electrode during charging, they can return to the same structure they started in, repairing any extra spaces or cracks that might have formed when the battery discharged.

Of course, cracks aren't the only things that limit rechargeable batteries, so it's important to find fixes for the other limitations before this hits the big time. "This means batteries could have far longer life spans, but also they could be pushed beyond levels that currently damage them," said corresponding author Professor Atsuo Yamada in a press release.

Still, this is a big step toward higher-capacity, longer-lasting batteries, which will make a big difference in everything from electrified transportation to the smartphone in your pocket.

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Learn more about the potentials of battery power in "Insane Mode: How Elon Musk's Tesla Sparked an Electric Revolution to End the Age of Oil" by Hamish McKenzie. The audiobook is free with an Audible trial. We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.

Written by Ashley Hamer June 13, 2019

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