Amprius Begins Shipping a Better Smartphone Battery

A company called Amprius is getting closer to delivering salvation from so-so smartphone batteries.

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Jared Newman /

A company called Amprius is getting closer to delivering salvation from so-so smartphone batteries.

As one of several companies trying to fix smartphone battery life, Amprius has begun supplying its first products to phone and tablet makers.

The exact improvement in real-world performance is tough to quantify without testing  old and new technologies side-by-side in the same phone, but the company estimates a 10-25% improvement at first, Amprius CEO Kang Sun said in an interview.

“This is already a substantial improvement from the batteries in the marketplace,” Sun said.

What the company can quantify is Watt-hours per liter–in other words, how much energy can be stored in a given volume. Amprius’ first smartphone battery, with 1850 mAh capacity, offers 580 Watt-hours per liter, compared to about 530 Wh/L for existing high-end batteries. Amprius is also offering a 4060 mAh, 600 Wh/L battery for tablets, and is working with phone makers on custom-sized batteries.

That’s just for Amprius’ first-generation technology. In 2014, Amprius is hoping to mass produce a second-generation battery with 670 Wh/L performance. A third-generation model, which CEO Kang Sun referred to as the “holy grail” of battery tech, could go into volume production the following year, and would provide upwards of 700 Wh/L.

“We’re certainly very excited. The market is very excited too,” Kang said.

The main problem facing conventional lithium-ion batteries for smartphones is that they rely on graphite, which stores energy in the anode of a battery cell. Graphite can only store so much energy, and battery makers are approaching the material’s theoretical limit.

Amprius and other companies are trying to replace graphite with silicon, but silicon’s tendency to swell and crack the battery while recharging is a major obstacle. With its first-generation battery, Amprius isn’t offering a full silicon anode yet, but is using a “nanomatrix structure” with fine silicon particles and other active electrochemical materials. The company claims that its batteries meet phone makers’ requirements of maintaining 80% capacity over 500 charges.

In its third-generation battery, Amprius plans to use nanowire technology developed by Stanford University professor Yi Cui that will enable a full silicon anode. Improvements to the cathode, which Amprius is also working on, could push battery life forward even further.

But it’s not all good news. For now, Amprius is producing its own batteries in a pilot line, while also partnering with a single battery manufacturer to boost production. That’s fine for small-scale output, but it’s not nearly enough to meet worldwide demand. In the United States, smartphone makers won’t use Amprius’ technology until it can be produced at much greater volumes, Kang said.

“Capacity is our biggest enemy today,” Kang said.

To meet demand, Amprius wants to break ground this year on its own manufacturing facility, where the company could produce 60 million mAh worth of batteries per year. But that requires significant investments, and right now Amprius only has “verbal agreements” from investors. (Amprius’ investor list includes some big names like Kleiner Perkins Caufield & Byers and Google Chairman Eric Schmidt.)

Even if Amprius begins mass-production this year, the facility would only handle the company’s first- and second-generation batteries. Full silicon anode batteries, using nanowire technology, would require a separate facility, Kang said.

In other words, it’s going to be a while before smartphone battery life will see any drastic improvements. Still, the launch of actual smartphone batteries with new chemistry and modest performance gains is a big milestone–and hopefully a sign that we won’t be stuck with middling battery life a few years from now.