The Galaxy S25 Edge Just Got Some Fresh Competition In The Super-Thin Phone Department

If you’ve been keeping an eye on the smartphone world lately, you’ve probably noticed that “thin is in.” Samsung has already confirmed the existence of its Galaxy S25 Edge, Apple is rumored to be launching an iPhone 17 “Air,” and nearly every foldable phone is trying to shave off extra millimeters. But it turns out thinness isn’t just for premium flagships. TECNO, known for its budget-friendly devices, is throwing its hat into the ring with the TECNO Spark Slim, set to debut at MWC 2025.

The company is touting the device as the “slimmest device with a 5,200mAh-plus battery.” If you’re wondering why it doesn’t just call it the thinnest phone ever, it’s because it isn’t. We’ve seen sub-5mm phones from OPPO and vivo a decade ago, but those devices packed much smaller batteries in line with the trends of that time. TECNO’s claim specifically ties its slimness to battery capacity, which is a notable distinction.

Still, a phone measuring just 5.75mm thick is an impressive engineering feat, especially considering the rumored ~6mm thickness of the Galaxy S25 Edge. What’s even more striking is that TECNO has managed to fit a 5,200mAh battery into this slim frame, while Samsung’s upcoming slim flagship is reportedly sticking to a much smaller 4,000mAh battery.

One of the biggest developments in smartphone batteries recently has been the adoption of silicon-carbon battery technology, which allows for greater energy density in smaller sizes. The OnePlus 13, for example, packed an enormous 6,000mAh battery while still maintaining a sleek profile. While TECNO hasn’t explicitly confirmed if the Spark Slim is using silicon-carbon tech, it does say the phone has a “4.04mm thick, high-density battery.”

The Spark Slim is crafted from fully recycled aluminum using an integrated die-casting process and features a stainless steel unibody design. For those of us who miss the days of metal-bodied phones (HTC fans, unite!), we can only hope this is the beginning of a comeback. Of course, given its metal back, it’s unlikely to support wireless charging (although technically, that’s not impossible). For what it’s worth, the phone does support superfast 45W wired charging.

A big part of making a thin phone look even thinner comes down to the side frame, and TECNO has gone with a curved display that slims down the edges for an even sleeker look. The 6.78-inch AMOLED panel boasts a 1.5K resolution, a 144Hz refresh rate, and a peak brightness of 4,500 nits. On the camera front, the device features a 50MP+50MP dual rear camera setup and a 13MP front-facing camera.

TECNO hasn’t revealed the exact chipset powering the Spark Slim, only referring to it as an “upcoming high-performance octa-core chip.” However, since the Spark lineup typically falls in the budget to mid-range category, it’s safe to assume this won’t be a flagship processor.

For now, TECNO hasn’t shared pricing or availability details for the Spark Slim. In fact, it’s unclear if the company plans to release it as a commercial product at all, as TECNO’s press release refers to it as a “concept smartphone.”

As for me, I’ll admit I’m less concerned about the thinness numbers and more excited about the shift toward high-energy-density batteries. If this trend continues, we might finally reach a point where multi-day battery life becomes the norm for smartphones. Sure, global brands like Samsung and Google might take their sweet time adopting such consumer-friendly tech, but for now, it’s refreshing to see companies like TECNO pushing the envelope.

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