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Whoop’s new fitness tracker is better thanks to a battery breakthrough

Whoop’s new fitness tracker is better thanks to a battery breakthrough


Sila Nanotechnologies’ silicon anode has finally arrived

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Fitness company Whoop has a new tracker that squishes five LEDs, four photodiodes, a pulse oximeter, skin temperature sensor, and more into a package that is 33 percent smaller than its predecessor — all while still offering five days of battery life. But a particular change to the tracker’s battery chemistry is one of the biggest reasons Whoop was able to do all this in the first place.

The change was pioneered by a Silicon Valley company called Sila Nanotechnologies, which was co-founded in 2011 by Gene Berdichevsky, one of Tesla’s earliest employees. And it’s one that, if it scales up, could help break some of the biggest limitations currently facing lithium-ion technology.

On paper, it’s a simple change: the battery’s anode is now made of silicon instead of graphite, which allows for greater energy density (up to 20 percent, Sila claims). Greater energy density means device makers can use a smaller battery to accomplish the same tasks — or free up more space to do things they couldn’t before. And it doesn’t require any hardware changes to the cell production process. In fact, that’s one of Sila’s biggest selling points to battery makers: its silicon anode is more or less plug-and-play.

In practice, though, this change was only possible after years of trial and error and millions of dollars spent. Sila toiled with a number of different so-called “precursors,” or raw materials, in order to find the right mix to be able to create its breakthrough silicon powder. And it did this with a mandate from Berdichevsky that those precursors had to be widely available — even if that made it harder to reach the theoretical performance jumps silicon anodes can provide.

Far greater energy density, which means more room for new features

“Those constraints, they sharpen the innovation,” Berdichevsky tells The Verge. “[But] they make it harder. So you have less degrees of freedom.”

As a result, Berdichevsky says it took Sila about twice as long as he originally hoped to get into a consumer product. But considering the supply chain shortages currently strangling just about every industry imaginable, it was a prescient decision to build on such a foundation. He also says it’s helped Sila attract a deep roster of smart minds from multiple highly competitive fields.

“Creative people love those really, really hard problems. And so I think that’s really what distinguishes us from from so many other [startups in the space],” he says. “You have less competition when you solve the hardest problems.

Sila also had to fight the natural tendency of silicon to expand and break down when used in a battery, because the reason it can store more lithium ions is that they actually briefly bond with the silicon — meaning the ions sort of have to be ripped out of the anode.

All of this is why Berdichevsky is so visibly happy to finally get his company’s battery science into the first consumer device when we talk via videoconference. It’s both a proof of the concept and of the myriad benefits that come with a more efficient battery.

Berdichevsky says he originally envisioned the first place Sila’s tech would appear would be in smartphones, since the batteries they use occupy so much space that could otherwise be allocated for flagship features like advanced camera systems. What he didn’t expect when founding Sila, though, was the boom in wearable tech, which opened up a lot of new doors. Whoop first started talking to Sila roughly two years ago, Berdichevsky says, and the company’s tech is coming to a few other consumer devices soon (though he declined to say what those would be).

“Having innovative technologies where size really matters is a really great place for a technology like ours,” Berdichevsky says.

The biggest potential for Sila’s silicon anode could be with much larger batteries, like the ones that power electric vehicles. It could help automakers create smaller, more affordable EVs without sacrificing range, or get even more miles out of the big battery packs found in larger cars. And as long as the company has in fact found a way to make sure the silicon powder it’s creating can withstand being constantly charged and discharged, it’s possible that Sila-powered EVs could fill up faster than modern ones.

Sila’s capacity will be limited until it builds a new factory later this decade

At the consumer device level, Berdichevsky says that Sila doesn’t necessarily offer companies like Whoop a shot at cost savings, since right now the production of its silicon powder is so limited. Sila would have to make far more of its material if it were to provide enough to help power fleets of EVs, but the benefit of scaling up to that level is that the relative cost of production would go down.

None of that will happen until at least mid-decade, though. Berdichevsky says his company is planning to build a much larger production facility, using the $590 million it raised in January. Until then, Berdichevsky says the company will have “very limited capacity.”

By the time that new facility is up and running, Sila is destined to have some company. Tesla CEO (and Berdichevsky’s former boss) Elon Musk said late last year that Tesla is working to increase the level of silicon in the anode of the batteries it uses. Other companies are working to swap graphite for silicon, too.

But Berdichevsky says he thinks there’s plenty of space for Sila to keep growing — not only because of the performance gains, but also because of how Sila’s business is currently structured. “We help [battery companies] deliver a higher performing battery that we do charge a premium for, and then we split that premium with them,” he says. “At the end of the day, if you’re making a better product, and customers just want to buy it, then there’s plenty to go around.”