Samsung has finally joined the silicon-carbon battery race with its latest batch of premium foldables packing the new battery tech. But details for this change were rather hard to spot on the spec sheets. The company has confirmed during media briefings that the Galaxy Z Fold 8 Ultra, Galaxy Z Fold 8, and Galaxy Z Flip 8 all use silicon-carbon batteries.
Even then, the resulting capacities are hardly record-breaking. The Fold 8 Ultra carries a 5,000mAh battery, the regular Fold 8 gets 4,800mAh, and the Flip 8 has 4,300mAh. Rivals from Honor and Motorola have already crossed the 6,000mAh mark. But the figures only tell part of the story.
What is a silicon-carbon battery?
Silicon-carbon batteries remain a form of lithium-ion battery. The key change happens inside the anode, one of the electrodes responsible for storing and releasing lithium ions during charging and discharging. Conventional lithium-ion batteries predominantly use graphite in the anode. Silicon can hold considerably more lithium than graphite by weight, giving battery makers a route toward higher energy density.
Higher density creates two useful options for phone manufacturers. They can fit more battery capacity into the same physical space, or retain a familiar capacity while making the battery thinner and lighter. Foldables stand to benefit considerably from either approach. Every millimeter recovered from the battery can be used to improve thickness, weight, or even endurance.
However, pure silicon creates its own engineering problems. It expands dramatically as it absorbs lithium during charging, then contracts as the battery discharges. Repeated expansion can crack the material, damage internal connections, and accelerate battery degradation. This is why silicon-carbon designs combine silicon with carbon-based material to better control that expansion.
How it helped the Galaxy Z Fold 8 Ultra
The best example of how this tech helped Samsung is with the Z Fold 8 Ultra. Its 5,000mAh battery is 600mAh larger than the 4,400mAh cell in the Galaxy Z Fold 7. That works out to an increase of almost 14%. Samsung made that jump while trimming the unfolded thickness from 4.2mm to 4.1mm. Both generations weigh 215 grams. The company also claims up to 27 hours of video playback, compared with 24 hours on the Fold 7.
An extra 600mAh may sound modest beside the giant cells now appearing in Chinese foldables. The global Honor Magic V6 has a 6,660mAh silicon-carbon battery inside a body measuring 4mm when unfolded. Meanwhile, Motorola’s Razr Fold uses a 6,000mAh silicon-carbon battery while measuring 4.6mm unfolded. It also supports 80W wired and 50W wireless fast charging, giving it a considerable advantage over Samsung on paper.
So when you pit it against the other foldables out there, the Z Fold 8 Ultra looks rather conservative. It would be easy to dismiss Samsung over this, but the official briefings gave us a better insight into the company’s priorities. Samsung emphasized performance, longevity, and safety. The company also said users should expect battery health consistent with previous Galaxy products. Samsung appears to be limiting silicon content or using a more conservative cell design until it has greater confidence in long-term behavior.
Similar to Apple, Galaxy devices are looking to refine the experience and improve user experience with new models rather than introducing big spec numbers. There’s an argument to be made for both sides of this, but considering the past incidents, Samsung’s cautious approach isn’t surprising.
This is only Samsung’s first step
Samsung has arrived late to silicon-carbon batteries. Other brands have already used to technology to push phone batteries beyond capacities that once looked unrealistic. The first Galaxy attempt may not be hitting headline-grabbing figures, but the direction is clear.
Future Galaxy phones could adopt higher silicon percentages and larger capacities. The technology could eventually reach conventional Galaxy S devices too, where it might enable thicker battery reserves or slimmer designs. For now, silicon-carbon has helped Samsung make its newest foldables thinner without leaving battery capacity behind. We are now getting the best-built foldables ever, and after years of 4,400mAh Galaxy Folds, I’ll take the small but deliberate step.