The smartphone market has witnessed its share of groundbreaking and quirky innovations. Some reshaped the industry, while others quickly faded after disappointing both users and manufacturers. Then there were ideas that sparked interest but failed to gain traction due to technological limitations at the time — one of them being slim phones. Once seen as a passing trend, ultra-thin devices quietly vanished. But now, a decade later, they appear to be making a comeback. So, why the sudden resurgence? Let’s take a closer look.
What’s Behind the Sudden Rise of Slim Phones?
If you’ve been keeping an eye on the smartphone scene, you’ve likely heard about the upcoming Galaxy S25 Edge. For those unfamiliar, the S25 Edge (previously rumored as the S25 Slim) marks Samsung’s return to the slim phone market. This move appears to be influenced by Apple’s soon-to-launch iPhone 17 Air, which is also generating plenty of buzz.
Samsung’s motivation is likely driven by the desire to stay ahead of the competition, which makes sense. However, it seems the company may be rushing things a bit, opting for a smaller 4,000 mAh battery. While it should still provide decent battery life, it’s far from the best Samsung could have offered. This raises the question of whether Samsung could have taken the time to properly test Silicon-Carbon batteries for better performance.
At MWC 2025, smartphone maker Tecno unveiled the Spark Slim, which packs a 5,200 mAh battery while measuring just 5.75 mm thick. This impressive feat is made possible by Silicon-Carbon battery technology, which uses a denser Silicon-Carbon anode that can store more power than the traditional graphite anode found in Lithium-ion batteries. The result is a 20-30% increase in overall capacity without compromising on size, allowing for more power in the same or even smaller dimensions compared to Lithium-ion.
The upcoming slim phones the Galaxy S25 Edge and iPhone 17 Air are rumored to be just 5.84 mm and 5.5 mm thick, respectively. Given that Apple and Samsung are typically slower to adopt the latest technology trends, it’s unlikely that either brand will feature Silicon-Carbon batteries. However, in true Android fashion of following Apple’s lead, we can expect more slim phones to emerge in 2025 as other brands start to mimic these moves.
A Glimpse into the Early Days of Slim Phones
Those who’ve been following the smartphone industry since the early 2010s may recall that Samsung has a history with slim phones. The Galaxy A8, released in 2015, was the company’s thinnest modern smartphone, measuring just 5.9 mm.
Soon, other manufacturers joined the race for slim phones. The Vivo X5 Max, for example, held the title of the slimmest phone ever made at just 4.75 mm. Similarly, the OPPO R5 measured 4.85 mm, and Motorola’s Moto Z came in at 5.2 mm. I still vividly remember seeing X5 Max advertisements everywhere when I was 14, leaving me in awe and wondering just how much thinner phones could possibly get.
Some of these slim phones featured impressive specifications for their time, including AMOLED displays, decent mid-range processors, and surprisingly, headphone jacks despite their thin profiles. Vivo even managed to fit a Yamaha DAC into the X5 Max, enhancing audio quality.
However, the battery capacity was often an afterthought. With just 2,000 mAh batteries paired with power-hungry 1080p displays and inefficient 28nm SoCs, these phones barely lasted three hours on a full charge.
Moto tried to address the poor battery life with custom Mods on the original Z and Z2, but despite the innovative approach, the Mods received an underwhelming response. The Z series also faced issues with software optimizations and quality control. Perhaps things would have turned out differently for the Z series had Moto tackled these problems.
It soon became clear to manufacturers that the technology simply wasn’t there to make ultra-slim phones work. Despite their best efforts, slim phones eventually faded from the market. But with a decade of advancements in optics and batteries, could slim phones finally succeed now? To find out, we need to look at another form factor for comparison.
Are Slim Phones the New Compact Phones?
It’s clear that manufacturers are bringing back slim phones to offer devices that are easier to hold and carry. If that sounds familiar, it’s because the same sentiment once drove the popularity of small phones. So, could slim phones now be stepping into the role compact phones once played?
While I would’ve been much more excited if Silicon-Carbon batteries were used in compact phones, slim phones do have their place. They’re easier to hold, slip into pockets effortlessly, and have a sleek, stylish look. All valid advantages but even then, they might end up feeling like an even more niche choice than small phones ever were.
On the other hand, small phones fulfill a core consumer need — one-handed usability — which made them slightly more appealing and practical than slim phones. Their compact size naturally delivers a better in-hand feel and superior pocket-friendliness. So, when it comes to choosing between a slimmer design with a larger screen and better portability with easier one-handed use, most would likely lean toward the latter.
The Trade-offs: What Does Thinness Really Cost?
If you’re set on getting a slim phone, don’t overlook the current slab smartphones that have already made impressive strides in both design and functionality. Many are already quite thin. Take the OnePlus 13, for instance. Its predecessor, the OnePlus 12, featured a 5400 mAh battery at 9.2 mm thick (excluding the camera bump). Yet the OnePlus 13 manages to pack a 6000 mAh battery while trimming down to just 8.5 mm. Similarly, the iQOO 13 has gone from 8.35 mm to under 8 mm.
The bottom line is that shaving off a few millimeters in thickness usually comes at the cost of a smaller battery, inferior optics due to space constraints, compromised structural integrity, and potential performance throttling. For the majority of users, these compromises might not justify the slimmer design.
While the debate between slim and small phones is interesting, it’s important to remember that both form factors are inherently niche. However, unlike small phones, slim phones don’t address any major needs they’re more about aesthetics than functionality.
While advancements in battery technology, efficient processors, displays, and other components may prolong the life of slim phones, this form factor still comes with compromises, and it may not endure in the long run. Slim phones are essentially stepping into the small phone market, but small phones remain the more practical choice.
Who Are Slim Phones Meant For? Will They Last in the Next Era?
The target audience for slim phones is clearly business professionals, executives, influencers, trendsetters, and users who prioritize aesthetics and minimalism. While slim phones have certainly improved compared to decade-old models, they remain largely driven by looks rather than functionality.
I believe this is where brands need to reinvent the slim phone category to cater to both slim and small phone enthusiasts. OnePlus seems to be aiming for this with its upcoming OnePlus 13T. While the exact specifications are still unclear, the rumored 6.32-inch screen, 7.8 mm thickness, and 5,800 mAh battery could make it the perfect balance. Additionally, the Xiaomi 15 offers another option with its 6.3-inch display and 8.1 mm thickness, blending small and slim features into one device.
The true small phone category effectively ended with the iPhone SE 3, but while they may not be strictly small, devices like the Galaxy S25, Pixel 9, and Xiaomi 15 continue to carry the legacy. These phones feature smaller displays with thinner bezels, improving reachability and pocketability. Some of them even include Silicon-Carbon batteries, and when paired with their already slim form factors, they make slim phones feel somewhat redundant.
While the Galaxy S25 Edge might still have the edge in sheer slimness, the difference will continue to shrink (pun intended) as more manufacturers adopt the new battery technology. This could make the trade-offs seem less significant, potentially leading to the second demise of slim phones.
What are your thoughts on slim phones? Do you think they’re superior to small phones? Let us know in the comments below.
