The OnePlus 15 Is the Latest Spark in a Battery Revolution Coming to Phones

When your phone’s battery gets really low, like down to 2%, what do you do? My guess is that you plug it in to charge or reach for a battery bank. If you can’t recharge, you turn on your phone’s low-power mode to eke out every last drop of power you have left. Well, that’s not what CNET’s David Lumb did when his phone was at 2%. He started playing the game Dead Cells on it.

No, Lumb isn’t a masochist; he’s a phone reviewer. After 45 minutes of gameplay, his phone finally dropped to 1%, at which point it automatically shut down. Lumb was reviewing the new OnePlus 15, which has a special silicon-carbon battery. At 7,300 mAh, it’s one of the largest capacity batteries of any phone that CNET has ever tested. For perspective, the iPhone 17 Pro Max has a 5,088-mAh battery and scored top in our CNET Labs battery tests in September.

Battery life is arguably the most important feature in any mobile device. In a CNET/YouGov survey, readers ranked “longer battery life” second only to price among reasons to upgrade to a new phone. The more we use our phones, the more we thirst for more hours away from the charger, and phone-makers are responding with longer-lasting batteries.

The OnePlus 15’s 7,300-mAh battery is enormous, but there are a handful of other phones that CNET has tested with a 7,000-mAh capacity battery or higher: Gaming phones such as the 2024 RedMagic 10 Pro and its follow-up, the RedMagic 11 Pro have 7,050-mAh and 7,500-mAh batteries, respectively. The Oppo Find X9 Pro has a behemoth 7,500-mAh battery but it isn’t sold in the US. I should note that OnePlus is a subsidiary of Oppo.

The secret sauce giving these phones such extraordinary capacity is that they have silicon-carbon batteries, a relatively new type of power source that can increase capacity without requiring a larger physical battery. That’s especially important in a phone, where battery size is severely limited.

“Silicon possesses a much higher energy storage capacity than graphite. Our innovation lies in integrating this material at an industry-high 15% content, which fundamentally enables greater energy density,” Rudolf Xu, OnePlus senior product marketing manager, told CNET. “Paired with the customized dual-cell design, it allows us to pack a massive 7,300-mAh capacity.”

OnePlus is one of a handful of phone-makers taking advantage of silicon batteries. And it’s only a matter of time before other device manufacturers follow.

Silicon-carbon vs. graphite batteries

Before you can really appreciate what OnePlus has done, it’s worth explaining some terminology. Battery capacity, measured in milliampere-hours (mAh), is just one factor that determines how long your phone lasts before you have to recharge it.

For example, Apple is able to control the design of the processor, software and all the hardware on its iPhones to get as much efficiency out of a battery as possible. Android phones like the OnePlus 15, on the other hand, come in various sizes, have different processors, run custom software skins on top of Android itself, and typically have batteries with a larger capacity because they can’t be nearly as efficient as Apple’s devices. Android phone-makers use a brute force method to overcome all those variables by shipping a phone with a battery capacity as large as possible.

Phone batteries have a cathode (positive electrodes) and an anode (negative electrodes), each made of different chemicals that sit in an electrolyte solution. When you charge your phone, the positive electrodes flow from the cathode through the electrolyte solution to the anode and are stored. This is an oversimplification of how a battery works, check out this iFixIt video that goes even more in-depth. But for this story, it’s the anode material that’s the real breakthrough with silicon batteries.

In a regular phone battery (iPhone, Galaxy phones), the cathode is made of a metal oxide like lithium cobalt oxide, and graphite is the anode material. What’s different in this new silicon battery (OnePlus 15) is that the cathode still has lithium, but the anode is silicon-carbon, which enables greater capacity in batteries of the same size.

I spoke with Rick Luebbe, the CEO and co-founder of Group 14, which developed the silicon-carbon anode for the 2024 Honor Magic 7 and 7 Pro. They’re the first phones to be released with this new type of battery.

“We’re replacing that graphite anode with the silicon-carbon composite. Because the electrochemistry is so different, we call it a silicon battery, even though it’s still lithium-based,” Luebbe explained.

The first generation of these new batteries debuted in 2024 and still used some graphite in the anode, which muted the capacity gains. For example, the OnePlus 13 had a silicon battery with a 6,000-mAh capacity, 1,300 mAh less than the OnePlus 15.

It’s one thing to have better battery life daily but longevity is another factor to consider. A battery’s lifespan is measured in charge cycles. One cycle consists of fully charging and fully discharging a battery which might not happen over a single day. How often do you fully charge your phone to 100% or drain it empty?

Xu says that the OnePlus 15’s battery is rated to have 80% of its capacity after 1,400 charge cycles, based on EU testing standards. That’s roughly 4 years of use. Apple says that the iPhone 15’s batteries are designed to retain 80% of their original capacity at 1,000 complete charge cycles. We have not been able to test OnePlus’ claims about its phone’s long-term battery capacity.

How does that extra capacity really show up in real life?

If you were hoping for 1.5 or 2 times more battery life, I’m sorry to disappoint you — silicon batteries don’t bring that dramatic of an improvement. However, in CNET Labs testing, the OnePlus 15’s battery life did show solid gains, and is one of the best you can get in the US.

CNET has two battery benchmark tests (video streaming and stress tests) that allow us to compare the performance of one phone against another. In CNET’s 3-hour video battery test, where we streamed a video over Wi-Fi with the screen at full brightness and the battery starting at 100%, the OnePlus 15 did excellent, even if the results were just behind the iPhone 17 Pro Max and our overall winner for this test, the Oppo Find X9 Pro. The Galaxy S25 Ultra dropped significantly lower when compared to the OnePlus 15’s performance.

In CNET’s 45-minute battery endurance test, during which we play games, stream videos, scroll social media and take a video call, the OnePlus did equally as well, tying with the iPhone 16E, OnePlus 13R, Poco F7 Ultra and the Moto G Stylus (2025). The iPhone 17 Pro Max, which dropped only a single percent, was the overall test winner and had the best result this year. The 2024 iPhone 16 Plus stayed at 100% (the best result for any phone).

In terms of real world use, aside from living on the battery’s edge and gaming for 45 minutes with just 2% left, Lumb found that the OnePlus 15 easily got through a day and a half on a single charge while using the phone casually. That’s on par with the iPhone 17 Pro Max and Oppo Find X9 Pro. Obviously, how you use your phone, the strength of your cell signal and how bright your screen is will affect your battery life.

So our testing shows that if you buy a OnePlus 15, you’re likely have a hard time draining its battery. But when you do need to recharge, the phone can do that fast.

Charging the OnePlus 15

Another advantage of silicon batteries is faster charging. In fact, get used to the term “flash charging.” Luebbe said the battery manufacturer, Molicel, has a cell today that can go from zero to fully charged in 90 seconds. This definitely seems like the early days for such technology, but it’s exciting to see where all of this could be headed.

“You’re no longer charging overnight. You’re literally charging while you’re making your coffee, or going to get the paper from the driveway, and you come back and your phone’s good for a day,” said Luebbe.

The OnePlus 15 doesn’t charge that fast, but it supports fast charging in the US and is one of the fastest charging phones CNET Labs has tested. In a 30-minute wired fast-charging test, its battery added 72%. It was fully charged after 45 minutes, and keep in mind it has that giant 7,300-mAh battery — or technically two 3,650-mAh batteries. Previous OnePlus phones have also had similar split batteries with the idea being that it’s faster to charge two smaller batteries to 50% than one larger cell. In fact, many of the fastest charging phones in our 45-minute test are from OnePlus.

I should also note that the global version of the OnePlus 15, available outside the US, supports 120-watt fast charging, which Xu says can fully recharge the battery in 39 minutes. The US version supports 100W fast charging, but comes with an 80W charger (OnePlus is the rare phone maker that still includes one with the phone). Most people would be more than happy with its 80W charging speed. By contrast, the iPhone 17 Pro doesn’t come with any power adapter and prices the 40W plug we used in the test at $39.

When will silicon batteries be in more phones?

The OnePlus 15 and other silicon battery phones are the beginning of an overdue revolution in battery chemistry. Not only will silicon enable improvements in battery life and charging, but it will also mitigate the impact of other battery-draining features, such as AI.

Qualcomm announced its 2026 flagship chip, the Snapdragon 8 Elite Gen 5, which powers the OnePlus 15 and other top-of-the-line phones. And while Qualcomm and other chipmakers focus on balancing power with efficiency, having a battery with more capacity means chipmakers could push the limits of a chip’s power without the fear of compromising a device’s battery life.

“Battery technology really hasn’t changed in a decade,” said Luebbe. “Being able to have such a dramatic advancement in battery technology is going to see [the] next wave of cellphone feature evolution happen quickly.”

So why aren’t silicon batteries more prevalent? Xu says that part of the challenge is that silicon anodes require specialized materials and precision engineering, which raise the costs.

“Achieving consistent reliability and performance demands sophisticated manufacturing capabilities,” noted Xu. “As the industry advances and production processes become more optimized and scalable, silicon-based battery technology is expected to gradually enter the mainstream.”

Luebbe sees manufacturing scale as the main challenge of getting silicon batteries to go mainstream. His company, Group 14, is the world’s largest manufacturer of silicon battery materials, according to press materials. And currently, the company manufactures roughly 30 to 50 tons of anode material a year.

“We project we’re in about 20 million phones right now,” said Luebbe about Group 14’s silicon anodes. “Apple and Samsung, they’re doing hundreds of millions of phones per year globally. So we need to be in hundreds of tons of production capacity.”

But Group 14 already knows this and has taken action. On my video call with Luebbe his Zoom background was an image of a new S. Korea factory that his company acquired. While never acknowledged, South Korea just happens to be the home to one of the largest phone-makers in the world, Samsung.

The focus of this story has largely been on smartphones, but really it’s the biggest and smallest devices that would benefit from silicon batteries the most, like electric vehicles, energy storage in homes or smartwatches and smart rings. Think about how much battery anxiety people will have alleviated as these new cells end up in more devices.

“Whether it’s the peace of mind from all-day battery life, the convenience of incredibly fast charging or the confidence in long-term battery health, we’ve taken care of it all,” said Xu. “This commitment ensures that OnePlus 15 doesn’t just meet your needs today — it’s designed to power your experiences reliably for years to come.”

Let’s hope so.