New Sila battery shows ‘dramatically higher energy density’ for wearables

13 Sep 2021

Image: © Artem Varnitsin/

The new technology fuels the Whoop 4.0 fitness wearable, which now boasts a 17pc higher energy density and a 33pc smaller device size.

A new battery innovation by Sila Nanotechnologies could represent a breakthrough in powering new wearables and mark a step forward for battery-powered technologies everywhere, if the science scales as planned.

Based in Silicon Valley, Sila was founded in 2011 to innovate in the area of battery materials. By focusing on silicon anode technology, it claims it has increased the energy density of its batteries by 17pc with the potential to boost it by as much as 40pc in future technologies.

Sila is demonstrating its battery’s efficacy in the Whoop 4.0 fitness tracker. This wrist-worn wearable, which has five LEDs and four photodiodes, is able to monitor blood oxygen levels alongside heart rate and skin temperature. It also uses a spinning motor so its alarm can silently wake up its user without disturbing others.

The company said that because of the new battery technology, these innovations didn’t result in a heftier design and even reduced the device size by 33pc.

“One of the greatest barriers to advancing the design of wearable technologies has been the weight and size of the battery technology available,” said John Capodilupo, co-founder and CTO at Whoop.

“With Sila, all that has changed. We’ve been able to transform Whoop 4.0 from its previous version and load it with new features and capabilities, without battery performance compromise. Just as we have leveraged this new battery advancement to push the wearable industry forward, Sila’s technology has the potential to enable exciting design innovation in other categories and products.”

Scaling up Sila

Lithium-ion batteries are a type of rechargeable battery that uses an anode and a cathode. An electrolyte carries positively charged lithium ions from the anode to the cathode through a separator. This movement creates free electrons in the anode, creating a charge. The current then flows from the current collector through the device to the negative collector.

Sila’s breakthrough works by replacing the graphite anodes in batteries with silicon, which results in better energy density without losing out on performance or safety.

The Whoop wearable is the first step in Sila scaling its technology. In January, it raised $590m in Series F funding, which brought it to a $3.3bn valuation. It said this money would be invested in new production capabilities, resulting in a new production facility by 2024 and batteries using its new anodes for electric vehicles by 2025.

Sila has existing ties with the electric vehicle industry after securing a partnership with BMW in 2018.

“After 10 years, 55,000 iterations and over a 1,000 times manufacturing scale up, the Sila team is the first to industrialise and now make commercially available a new type of lithium-ion chemistry with dramatically higher energy density,” said Gene Berdichevsky, CEO and co-founder of Sila.

“Our next-generation materials will drive radical change in product innovation, freeing consumers and device makers from having to choose between better design, more features and battery performance.

“We are running out of time to transition from the fossil fuels economy to the energy storage economy. The path to a sustainable future will be paved with great products and Sila is proud to be enabling those products today.”

The race for new battery technologies is ongoing, as Toyota recently announced a planned $13.6bn investment by 2030. It is focusing on all-solid-state batteries for its vehicles. These batteries are currently prone to a short battery life, which the car maker is working to solve.

Sam Cox was a journalist at Silicon Republic covering sci-tech news