Why I think this super-thin phone is more exciting than the Galaxy S25 Edge
Tecno's Spark Slim concept has a big battery to shame Samsung
Didn’t you hear? Thin is in. Or rather it will be, with upcoming phones like the Galaxy S25 Edge and iPhone 17 Air set to slim down to size zero proportions. Chinese firm Tecno got there first, though. The Spark Slim concept revealed at Mobile World Congress has a battery that leaves both Samsung and Apple in the dust.
At 5.75mm, the Spark Slim really is wafer-thin. The Galaxy S25 Edge is predicted to be closer to 6mm, while Apple’s effort is more of a mystery. I was more impressed with how light it felt in my hand. It tips the scales at a mere 144g – and Tecno’s engineers actually had to add some extra heft, because an earlier prototype felt too toy-like. Slender fans will barely feel it in their pocket.
The real achievement is squeezing a 5200mAh capacity battery inside something so slim. Samsung doesn’t look to be adopting silicon-carbon battery tech any time soon, and leaks suggest the S25 Edge will make do with a mere 3900mAh. The Tecno – which is slimmer – bests it by 25%. That could make a major difference when it comes to time away from the mains.
I saw two versions: one with a polished silver rear and one in white ceramic. They needed regular polishing to keep them free from fingerprints. Both have curved front and rear panels that bend inwards to give a much shallower grip point than I’ve gotten used to from the current crop of flat-sided flagships. Illuminated strips around the rear camera lenses add a bit of character.
You’re getting twin 50MP rear snappers here, along with a 13MP selfie cam that uses the near-universal central punch hole arrangement. It’s set into a 6.78in curved AMOLED screen, with a 3K resolution and 144Hz adaptive refresh rate. Peak brightness is pegged at 4500 nits, which is enough to trade blows with today’s best flagships.
Power comes from an unannounced chipset, while RAM and storage have yet to be locked down. Tecno’s rep told me that lots of phone shoppers simply don’t pay attention to specs, but take notice when something feels noticeably slimmer or lighter in their hands. That suggests mid-range performance to me.
Tecno used the skinny components usually reserved for top-tier foldables, like a custom USB-C charge port, and the rear camera module has to protrude a bit – but seemingly nowhere near as much as Samsung’s S25 Edge prototypes. That does suggest pricing could be on the spicy side, though.
The Spark Slim is just a concept right now. If Tecno puts it into production, I’d expect it to stay firmly within the company’s established markets like South East Asia and Africa. But unlike the “look but don’t touch” Galaxy S25 Edge, this phone feels very much ready to go.
Tom Morgan-Freelander
Deputy Editor 
