Phone makers used to spend years chasing the thinnest flagship possible, and buyers mostly shrugged.The sales numbers have been in for a long time; the compromises are obvious, and I still don't get why there are attempts at bringing thin phones back.Still, here's why an extra millimeter or two is worth it.
The case for thicker phones Every millimeter shaved costs you something real Close Thinness makes a great keynote moment, but you don't use a phone on a stage.You use it on a commute, at the end of a long day, with 12% left and no charger in sight.Every millimeter an engineer takes out of a chassis has to come from somewhere.
Most of the time it comes from the battery, the camera module, or the space that keeps the processor cool.The Galaxy S25 Edge shows this clearly.It was an impressive piece of industrial design, but the slim frame came with trade-offs buyers noticed right away.
The phone measured just 5.5mm and carried a 3,900mAh battery, and its high price combined with that reduced capacity drew criticism.At flagship pricing, people weren't willing to accept a phone that did less just because it looked sleeker.Thermals matter too.
Modern mobile chips are powerful, and they get hot when you push them with gaming, video recording, or on-device AI.A thicker body has more room for vapor chambers and graphite sheets, so the phone can sustain performance longer before throttling.A thin slab has less material to spread heat, so it gets warm faster and slows down sooner.
There's also the matter of cameras.Large sensors and periscope telephoto lenses need physical depth.Make the phone thinner, and you either drop a lens, shrink the sensor, or end up with a camera bump that sticks out even further.
That defeats the point of a thin phone, since the thickest part of the device is what determines how it sits on a table or in a pocket.Finally, a slightly chunkier phone is easier to hold.Most people put their phone in a case anyway, which adds far more bulk than the millimeter or two manufacturers fight over.
Apple openly embraces the thickness on its iPhone Pro line — not counting the iPhone Duo, the iPhone 18 Pro Max is Apple's heaviest phone to date, but it also has the best battery life you can find on an iPhone.For me, that's an okay compromise.Why the thin trend is passing away Buyers voted with their wallets, and they chose battery life Trends in smartphones come and go, and the ultra-thin flagship already looks like one of the shortest-lived.
The clearest signal came from Samsung, the company that arguably kicked off this round of slim phones on Android.The sales figures told the story.About three months after its May launch, the Galaxy S25 Edge had sold roughly 1.31 million units, compared to 12.18 million for the S25 Ultra and 8.28 million for the base S25.
For a phone Samsung marketed heavily, that's a hard number to ignore.Samsung's response was pretty solid.Reports from Korea said the company canceled the Galaxy S26 Edge after disappointing S25 Edge sales, shifting priorities toward the more conventional Plus model once it confirmed demand for ultra-slim flagships was weaker than expected.
A Samsung official reportedly described the slim phone concept as practically gone, though the company didn't fully rule out reviving it under different circumstances.Instead, the company focused on its familiar three-phone lineup for 2026: the Galaxy S26, S26+, and S26 Ultra.With Samsung's new foldables out, including the Galaxy Z Flip 8, a new passport-shaped Z Fold 8, the Z Fold 8 Ultra, and even a Z TriFold to spice things up, there was no S26 Edge, and it's probably safe to say that the S25 Edge was a one-off.
Apple's thin phone wasn't great either.The iPhone Air didn't fly off the shelves, and while we're rumored to get an iPhone Air 2 sometime next year, it's probably also getting the axe after that one launches.Really, what buyers actually want isn't a mystery.
Extra lenses, full-day battery life, and better heat dissipation appear to matter more to buyers than an ultra-slim, lightweight design.Thin phones generate headlines and early curiosity, but once the novelty wears off, people look at the compromises and move on.Lesser batteries and, worse, less versatile cameras are things some folks will not settle for.
That doesn't mean slim designs will vanish entirely.Foldables still depend on thin halves, and some brands will keep experimenting.But as a mainstream flagship strategy, thinness for its own sake has run into the wall of what people use their phones for.
Manufacturers follow sales, and sales are pointing toward phones that last.The silver lining: silicon-carbon batteries Better chemistry could end the thickness trade-off The thin phone experiment wasn't a total loss, because it pushed attention toward a battery technology that could change the equation entirely.Silicon-carbon batteries swap the traditional graphite anode for a composite that can store more lithium ions in the same physical space, delivering much higher capacities without dramatically increasing thickness or weight.
Chinese manufacturers have already embraced it.Brands like Honor, Oppo, OnePlus, and Xiaomi have been pushing batteries beyond 7,000mAh.Samsung has been far more conservative.
The Galaxy S26 Ultra, released in early 2026, still ships with a 5,000mAh battery, the same capacity that debuted on the Galaxy S20 Ultra.That may change soon, though.Ahead of Galaxy Unpacked 2026, Samsung's head of smartphone R&D, Moon Sung-Hoon, said the company is actively preparing a phone with a silicon-carbon anode battery that will arrive in due course.
The technology isn't flawless.Silicon can expand significantly as it absorbs lithium ions, which causes stress, swelling, and faster degradation over time.That's a real concern for companies promising years of software updates.
There's also a regulatory hurdle.Battery cells above 20Wh must be declared as dangerous goods for transport in Europe, which is roughly 5,200mAh at typical smartphone voltage, and similar rules apply in the US.That's why devices like the Xiaomi 15 Ultra ship with smaller batteries in Europe than in China.
One workaround is splitting capacity across two cells, but Vivo has argued that multi-cell batteries take up more space and make phones thicker and heavier.Here's the twist.If a slightly thicker phone is what it takes to fit a dual-cell silicon carbon battery, that's a trade worth making.
Better chemistry paired with a sensible chassis could deliver two-day battery life without a brick in your pocket.I still don't think phone makers will focus fully on thinness, though, but it could help solve battery-life problems on foldable phones.Thicker phones, bigger batteries, and a better future Ultra-thin flagships promised elegance but delivered compromise, and buyers noticed.
With Samsung retreating from slim designs and silicon-carbon batteries maturing, the smartest path forward is a phone with a little more heft and a lot more stamina.
Read More
