Samsung is Working on an Insanely Big Battery Phone, But There’s a Problem

While rivals such as OnePlus and Honor have moved toward larger silicon-carbon batteries in recent smartphones, Samsung has so far taken a more conservative approach. Even recent flagship devices like the Galaxy S25 Ultra and Galaxy S25 Edge continue to rely on lithium-ion batteries with lower capacities.

A new report suggests that Samsung may be working on something far more ambitious behind the scenes.

Dual-Stack Battery

According to a report from Android Headlines, citing a source on X, Samsung SDI is testing a dual-stack silicon-carbon battery with a combined capacity of an impressive 20,000 mAh.

The reported design involves stacking two silicon-carbon cells together. One cell is said to have a capacity of 12,000 mAh, while the second measures 8,000 mAh, resulting in the unusually high total capacity. This approach would increase battery thickness but significantly boost energy storage.

The Main Problem

The report notes that Samsung has been testing this dual-stack battery configuration for over a year, completing approximately 960 charge cycles. During testing, the smaller 8,000 mAh cell reportedly expanded in thickness from 4mm to 7.2mm, indicating a swelling issue and raising concerns about long-term durability.

Despite the swelling problem, the battery reportedly delivered around 27 hours of screen-on time per charge during testing. However, the expansion issue is considered a major obstacle that Samsung must resolve before commercial use.

If Samsung SDI manages to address the swelling and longevity challenges, the technology could eventually appear not only in Samsung-branded devices but also in smartphones from other manufacturers that source batteries from Samsung or may do so in the future.

For now, there is no indication of when or if this 20,000 mAh dual-stack battery will reach consumer products. Still, the report suggests Samsung is actively exploring battery designs that go well beyond current smartphone capacities.