Should you buy a phone with a silicon-carbon battery? Here’s the catch

Battery life; we can never have enough of it. Even though most smartphones from the past few years will easily take you through a day of use and possibly even two, the oldies among us still pine for those good old days when a single charge was enough to take your feature phone through a busy week.

Thankfully, battery engineers are on the case, and many of today’s best flagship smartphones are now shipping with new silicon carbon batteries. This allows them to boast even larger battery capacities without a thicker or larger chassis. Talk about a major win.

For example, the OnePlus 13 packs a 6,000mAh silicon-carbon battery, allowing for an increase on last year’s 5,400mAh cell. The Xiaomi 15 Ultra also boasts a colossal 6,000mAh battery capacity in China, up from 5,400mAh in the previous year (and a still decent 5,400mAh for global markets, up from 5,000mAh), and the smaller models benefit from similar gains, too. The HONOR Magic 7 Pro, OPPO Find X8, and the vivo X200 series are equally new flagship models boasting silicon in their power cells. The technology is already here in earnest.

Unfortunately, we haven’t seen Apple, Google, or Samsung adopt silicon-carbon battery technology into their latest products just yet. Perhaps we’ll see these brands leap onboard closer to 2026. Still, should you rush out to buy a phone with a silicon carbon battery, or should you stick with the more familiar Lithium-ion models we know and love?

Today’s new silicon-carbon (Si/C) Li-Ion batteries are actually an evolution of traditional lithium-ion technology rather than an entirely new concept. They modify the conventional graphite anode by infusing it with silicon, which can store much more energy — theoretically up to 10x more than graphite (372 mAh/g versus ~4200 mAh/g for pure silicon). This has long made silicon an exciting material for boosting battery capacity.

However, pure silicon anodes have significant challenges. The most problematic is extreme expansion, with the structure swelling by up to 300% when fully charged. This puts severe mechanical stress on the battery, reducing lifespan and causing structural failure. Additionally, silicon reacts aggressively with the electrolyte, breaking and reforming the Solid Electrolyte Interphase (SEI) layer with each cycle, leading to lithium loss and reduced capacity over time. This is made all the worse by aggressive expansion. Silicon also has lower electrical conductivity than graphite, which can slow charge and discharge rates and increase losses due to internal resistance, which can result in more heat, another no-no for battery longevity.

A silicon-carbon (Si/C) composite is used instead of pure silicon to solve these issues. Carbon provides structural support, helping to mitigate expansion and stabilize the SEI layer. While traditional graphite anodes expand by only ~10% during charge cycles, a well-engineered Si/C battery may limit swelling to just 10-20%, depending on its silicon content. Carbon also improves electrical conductivity, ensuring better lithium-ion flow for improved efficiency.

The trade-off is that Si/C anodes don’t achieve pure silicon’s full 10x capacity boost. Instead, they offer a more modest 10-20% increase in energy density, depending on silicon content. Higher Si content provides greater capacity but also increases swelling and manufacturing complexity, making Si/C batteries an engineering challenge. There’s no such thing as a free lunch — Si/C batteries undoubtedly improve performance but with some limits and trade-offs.

Of course, any boost to smartphone battery capacity is a welcome one, and Si/C batteries are a boon for power users looking for smartphones that can withstand far more than a single day of heavy use. It’s no surprise that we’ve seen the technology arrive in so many of the most powerful flagship phones on the market this year.

I’ve been using the OPPO Find X8 Pro as a daily driver for over a month now and can attest to just how long-lasting its 5,910mAh Si/C Li-ion battery really is. I regularly make it through two days of moderate use on a single charge, have plenty left in the tank after a day out capturing the little ones, and lighter weeks have sometimes made it well beyond 48 hours before reaching for a charger.

Equally, however, Si/C is good news for thinner devices, such as foldable and lightweight phones. While the Galaxy S25 Edge might not debut Si/C for Samsung, thin or compact smartphones could undoubtedly benefit from this new battery type to retain reasonable capacities in more restrictive form factors. The vivo X Fold 3 Pro has already used the technology to pack a substantial 5,700mAh battery into a 5.2mm folding design. Samsung’s Z Fold 6 is 5.6mm thick yet only has a 4,400mA conventional battery. The most recent Chinese clamshell phones have leaped on this trend for larger capacities, too.

The big question hanging over silicon-carbon batteries is whether they’ll last as long as their more traditional lithium counterparts. With the trade-offs outlined above, it’s clear that Si/C won’t last as long as the most durable graphite-based Li-ion cells on the market today. However, lower levels of silicon content can still result in slightly higher-capacity batteries that will still last a similar length of time to traditional Li-ion cells. This looks like what we’re seeing in today’s most cutting-edge smartphones, with only a moderate but still very welcome boost in capacity to keep the silicon content in check.

As a result, smartphone brands may also be becoming more conservative with fast-charging temperatures to extend battery lifespans, especially as Si/C batteries push the boundaries of energy density and charge rates. That or brands are simply trying to ensure their phones can last as long as their recently improved five-plus years of promised updates. That said, Si/C is actually a boon for faster charging due to its improved capacity, higher lithium diffusivity, and lower risk of plating the anode. Not to mention that larger capacities make it more feasible to stick to the rule of 80% charge without the risk of running out of juice part way through your day. Silicon need not be bad news for keeping your handset for many years to come.

Si/C Li-ion batteries are clearly great news for the latest smartphones and will almost certainly improve the battery life of your wearables, tablets, laptops, and even electric vehicles. Silicon cells are already a key part of today’s most innovative handsets, enabling even larger capacities or thinner form factors without compromising on battery life.

Currently, however, you’ll have to shop around at brands from China to get a hold of one, such as the very impressive OnePlus 13. US mainstays Apple, Google, and Samsung are yet to leap on board with this new battery technology. They might not even get to it this year, leaving us waiting until their 2026 flagships or perhaps even longer before they join the party.

Still, it might be best to wait and see how the longevity issue plays out if you’re planning to keep your smartphone for more than five years. While battery replacements are pretty much inevitable with any long-term purchase, Si/C Li-ion cells could need replacing more regularly, especially when paired with fast charging. Given that they are more expensive to produce, this could end up being an unwelcome added cost for early adopters. We’ll have to wait and see.

Likewise, it’s not necessarily worth springing for a phone just because it has a Si/C Li-ion battery, especially if you’re on a tighter budget. Owing to its tricker manufacturing process, the technology is mainly reserved for flagship smartphones and novel form factors, and it might take several years before we see it trickle down to the mid-range segment. While there are battery benefits to be had with silicon carbon, a 12% larger capacity is not necessarily worth spending $100s extra on.