Samsung Tests Massive 20,000mAh Silicon-Carbon Battery

When it comes to battery capacity and charging speeds, Samsung has been one of the slow movers in the smartphone industry. No Galaxy phone currently charges faster than 45W, and battery capacities have largely been capped at 5,000mAh. That may soon change, though. Rumors suggest Samsung could introduce 60W charging with the upcoming Galaxy S26 Ultra. The company is also reportedly testing ultra-high-capacity silicon-carbon batteries reaching as high as 20,000mAh.

Samsung may be laying the groundwork for a major leap in smartphone battery

According to fresh rumors, Samsung’s battery arm, Samsung SDI, is experimenting with an unusually large 20,000mAh battery. Tipster @phonefuturist claims that the company is testing a dual-cell silicon-carbon battery design consisting of a 12,000mAh primary cell paired with an 8,000mAh secondary cell. While we don’t have the full dimensions, the two cells reportedly measure 6.3mm and 4mm in thickness, respectively.

That said, the batteries used in this test were probably too big to fit in a regular smartphone. Si-C batteries may allow for higher capacity in smaller sizes, but the tech still isn’t advanced enough for a normal-size handset to be able to pack a 12,000mAh battery. For the uninitiated, conventional batteries rely on graphite anodes, while silicon-carbon batteries replace graphite with a silicon-based material, which can store significantly more lithium ions for higher energy density.

This technology isn’t entirely new, but it has mostly been limited to early-stage implementations, particularly on phones. In this test, Samsung allegedly achieved an average screen-on time (SOT) of over 27 hours, allegedly measured across 960 charge cycles over a year. While early performance results appear impressive, the test reportedly ended with a critical issue. Post-validation analysis detected cell swelling, which led to the battery being classified as a longevity failure.

Battery swelling is a well-known challenge with silicon-carbon chemistry. Silicon can store significantly more energy than graphite, but it also expands and contracts more during charge cycles. Over time, this mechanical stress can compromise structural stability, especially in compact devices like smartphones. Samsung must be working on resolving the long-term stability issue with these batteries. Multi-day battery life may one day become the norm, but the path remains filled with engineering hurdles.