Redmi Reportedly Testing Phone With Massive 8,500mAh Battery That’s Still Under 8.5mm Thick

Chinese smartphone makers seem to be in the middle of a battery size race, and Xiaomi’s Redmi brand might be preparing one of its biggest moves yet.

According to a new leak, Redmi is testing a phone with an 8,500mAh battery — a huge step up from its already large-capacity models.

Pushing Battery Limits Without Adding Bulk

The leak, coming from well-known tipster Digital Chat Station, suggests that this new Redmi device will pack nearly 1,000mAh more than the recently launched Redmi Turbo 4 Pro (POCO F7 for the global markets), which already ships with a 7,550mAh cell. Despite the bigger battery, Redmi is reportedly keeping the phone’s thickness under 8.5mm.

That’s impressive when you consider that the Galaxy S25 Ultra — with a much smaller 5,000mAh battery — comes in at 8.2mm. Managing this balance between size and battery life likely comes down to advances in internal battery tech rather than bigger or heavier casings.

Silicon-Carbon Batteries Make It Possible

At the heart of this leap is silicon-carbon battery technology, which is becoming more common in China this year. Traditional graphite batteries top out at around 372mAh per gram. Silicon-based materials, on the other hand, can theoretically store up to 4,200mAh per gram, offering higher energy density and better lithium storage capabilities.

That means more power without shortening the battery’s lifespan. Silicon-carbon cells also help reduce lithium buildup — a problem that can cause short circuits in some cases. With this tech, phones with 7,000mAh or higher capacities have become increasingly common, and now brands are pushing toward the 8,500mAh to 10,000mAh range.

What Could This Mean for Everyday Use?

While most flagship phones focus on performance, camera hardware, and display tech, battery capacity remains one of the biggest pain points for heavy users. A jump from 5,000mAh to 8,500mAh could mean multi-day battery life for many people, even with high-refresh displays and demanding apps.

It’s still unclear which model will debut this larger battery, or when it might hit the market. Given the trend, though, we could see other brands follow quickly — Honor has already been rumored to be working on a phone with a 10,000mAh battery.