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How it started
Smartphone batteries are bigger than ever, while the phones themselves are shrinking. But whether you’re seeing the benefit — thin phones with big batteries — depends on where you live.
The key is the introduction of silicon-carbon batteries, which make it possible to fit more battery capacity into the same size cell, as in phones like the Honor Power, whose 8,000mAh battery delivers more power than some iPads. The flip side of that is putting the same capacity into much smaller cells, seen in the likes of the Oppo Find N5, a foldable phone that’s as extraordinarily thin as Samsung’s Galaxy Z Fold 7 but has a 5,600mAh battery that wouldn’t be out of place in an Ultra-sized flagship.
Honor and Oppo aren’t the only companies on board. Huawei, Xiaomi, Vivo, OnePlus, Nothing, and more have all released phones using silicon-carbon batteries. It’s not just phones, either; Whoop wearables have used silicon-carbon batteries since 2021 thanks to a partnership with Sila Nanotechnologies, and EV manufacturers from General Motors to Porsche have invested heavily in the technology.
But you’ve probably noticed some pretty big names missing from that list — none of Apple, Samsung, and Google, the three major players in the US phone market, have embraced the new batteries yet. That’s despite the fact that between Samsung and Google’s foldable phones, and super-slim models like the newly announced iPhone Air, the possible applications are immediately obvious.
How it’s going
“Silcon-carbon batteries” is arguably a bit of a misnomer, because these don’t replace lithium batteries — they’re a subset of them. In the broadest strokes, the bulk of a battery is made up of two parts, the cathode and the anode, and it’s the movement of ions between the two that either charges or discharges the cell.
In most modern batteries, the cathode is lithium-based, while the anode uses graphite. It’s that bit that silicon-carbon batteries change, using a blend of silicon and graphite for the anode. Silicon has almost 10 times the energy density of graphite, so just a little goes a long way — Honor’s recent Magic V5 foldable is the first to replace 15 percent of the graphite with silicon, and other phones have used as little as 5 percent.
More silicon means better battery capacity in the same space, so the race is on to push those numbers up. The reason manufacturers can’t go all in and swap all the graphite for silicon is that its energy density comes with one big downside: longevity.
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