Samsung showcased its long-rumored slim phone at the Galaxy Unpacked event in January, and Apple is expected to be developing an iPhone 17 Air. But it’s Tecno that has a truly ready slim phone that doesn’t compromise on battery capacity. The Tecno Spark Slim is what I expect a company to launch when it has the word “Slim” in the moniker. It’s got a 5,000mAh+ battery, less than 6mm thickness, and more than one camera.
Tecno announced the launch of the “world’s thinnest smartphone” a couple of days before Mobile World Congress 2025. I got my hands on the working prototype, which is said to be ready for a “staggered launch.” Here’s why I think this is what the Galaxy S25 Edge and iPhone 17 Air should be.
A bigger battery than the Galaxy S25 Ultra
Based on rumors, Apple and Samsung are expected to compromise on the battery capacity of their slim phones. For context, the Samsung Galaxy S25 Ultra features a 5,000mAh battery, and the Galaxy S25 Edge will likely have a smaller battery.
However, the Tecno Spark Slim packs a 5,200mAh cell that is bigger than most mainstream flagship smartphones. It carries this in a slimmer form factor than every phone on the market right now. With that capacity, it is likely to feature all-day battery life.
The Tecno Spark Slim measures 5.75mm thin. By comparison, Samsung’s base Galaxy S25 is 7.2mm thick, while the Galaxy S25 Ultra goes up to 8.25mm. As for Apple, the iPhone 16 is 7.8mm thick, whereas the iPhone 16 Pro Max measures 8.25mm. The Galaxy S25 Edge is said to be around 6mm in thickness.
It fits the 5,200mAh battery without compromising on fast charging. You get the same 45W charging speed that you’d find on the Galaxy S25 Ultra. It’s amazing that they fitted a big battery that charges fast in a 5.75mm slim form factor.
Tecno Spark Slim is everything you’d want from a thin phone
In my hands-on, the Spark Slim felt like a phone that I’d love to use. It features a 6.78-inch AMOLED display with curved sides. Unlike the Galaxy S25 Edge’s flat sides, the curved sides make the Tecno phone seem slimmer than it actually is. The in-hand feel is great—close to what you’d expect from a 2015 phone but with a bigger, sharper, and better display.
The screen was easily legible in bright indoor lighting. It is rated to deliver 4,500 nits of peak brightness on supported content. The Tecno Spark Slim was also smooth to scroll through the interface, thanks to the 144Hz refresh rate on the display. It packs a 13MP selfie shooter, too.
Tecno hasn’t specified the chipset information on its latest phone. All we know right now is that it’s an octa-core processor. I’m skeptical about the heat management system if it fits a flagship processor in this design, but we’ll wait and see. For now, I can confirm that it supports Google Gemini.
The Tecno Spark Slim sports a dual rear camera setup on the back. Both cameras have 50 megapixels to deliver sharp photos. I don’t expect them to be Samsung or Apple quality, but it’s good to have a dual-camera setup when the iPhone 17 Air is rumored to have a single rear camera.
While the Tecno Spark Slim seems like a fantastic thin phone, it’s still a concept. It is said to have a staggered launch, but there is no definitive launch date yet. I’m all in on slim devices if they don’t compromise on screen quality and battery capacity.