This lithium-ion battery kept going (and going and going) in the extreme cold

This lithium-ion battery kept going (and going and going) in the extreme cold thumbnail

Few inventions are more valuable than the simple lithium-ion battery. It’s been only 30 years since they first left the lab, but they’re what power smartphones in the world’s palms and put electric cars on the road. They will only be more important as essential components of renewable energy grids.

Since the early 1990s, these batteries’ prices have fallen more than thirtyfold, even as they’ve grown ever more powerful. They aren’t perfect. They struggle in extreme cold. These batteries are unable to hold their charge at temperatures that would not be unusual for anyone who has experienced particularly harsh winters.

But scientists are working to create stronger batteries. In a paper published in the journal ACS Central Science on June 8, chemical engineers from several universities in China have worked together to build a better battery that holds up as low as minus 31degF.

Scientists have known that lithium-ion batteries flatline at minus 4 degrees Fahrenheit. This is based on past research. They don’t retain as much charge and are less efficient at transferring it, so it’s more difficult to use them as power. They perform worse the colder they get.

Subzero temperatures aren’t an issue for most people around the world. If you live in the American Midwest, however, your electric car may have less range in January. If you’ve ever been outside in freezing winter, you might have noticed a faster draining of your battery.

[Related: We need safer ways to recycle electric car and cellphone batteries]

This drawback also means that lithium ion batteries won’t work as well in places where it is often subzero: high up, in the air where commercial aircraft fly, or in cold unlit spaces.

So there’s abundant research that addresses the problem, according to Enyuan Hu, a battery chemist at Brookhaven National Laboratory who wasn’t involved in the paper. Engineers and chemists must work with the battery’s internals to achieve this.

A lithium-ion battery is composed of two electrically charged plates. One plate is negative and the other is positive. The middle space is filled by an electrolyte, an electrically conducting slurry that contains dissolved ions. The negative plate is usually carbon-based, such like graphite; while the positive plate contains atoms both of metal and oxygen.

And lithium ions are what makes the battery tick–hence its name.

As the battery runs, the ions drop from the positive plate and cross the electrolyte, like fish moving down a river. They then land on the negative plates, delivering constant surges of electricity. The electric current causes ions to flee the opposite direction when you plug in a battery to charge it. It works without any problems and the moving lithium ions can fuel your car or phone for hours.

It works until the temperature of the battery drops below minus 4degF. Scientists have discovered that the problem is largely due to the movement of the electrons, which fail to properly leave the electrolyte and land on a negative plate. Scientists have attempted to solve this problem by creating stronger electrolytes that can withstand colder temperatures.

These researchers took a different approach. They experimented with the carbon-based negative plate instead. They decided to replace graphite with a completely new material. They heated a cobalt-containing compound to very high temperatures–nearly 800degF–producing little nuggets, shaped like 12-sided dice, made from carbon atoms. These carbon dodecahedra were made into a plate that is bumpier than flat graphite to allow it to grab more lithium ions.

When they tested their battery, they found that it worked at temperatures as frigid as minus 31degF. Even after over 200 cycles of discharging, charging, and recharging, this battery kept up its performance.

” The material is scientifically intriguing,” says Hu. “But its practical use may be limited because it requires [a] complicated synthesizing route .”

That’s the catch. It is difficult to create more of these tiny carbon orbs, as with many other materials. The cobalt compound is quite expensive. Hu claims that this research could be useful for specific applications.

It’s not the end of this quest, but it’s just the next step. Scientists are pushing the limits of these vital batteries every day.

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