The Problem with these Smartphone Batteries

Summary

MKBHD investigates why major smartphone companies like Samsung, Apple, and Google are avoiding silicon carbon batteries despite their impressive advantages. Silicon carbon batteries offer dramatically higher energy density — phones like the Honor Power 2 pack 10,000 mAh while being thinner than an iPhone 17 Pro Max with its 5,000 mAh battery. Chinese manufacturers like Xiaomi, OnePlus, Realme, Honor, Oppo, and Huawei have embraced the technology, with OnePlus jumping from 5,400 to 7,300 mAh in a single year.

The real reason for holdouts, MKBHD reveals through industry sources, is a serious swelling and longevity concern. Silicon expands up to three times its original volume during charging as it absorbs lithium ions, creating mechanical stress that can lead to internal cracking and potential thermal runaway. Some devices reportedly use literal steel cages around batteries to prevent swelling. While error rates can get below one in 250,000, at Samsung or Apple’s scale of tens of millions of phones, that could still mean dozens of exploding devices. The video also connects this to the US market being software-focused with strong ecosystem lock-in, reducing the competitive pressure to adopt risky new battery technology.

Highlights

”10,000 mAh and Thinner Than an iPhone”

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“This is the Honor Power 2. Yes, it’s absolutely a clone of the iPhone, but it’s also thinner than the iPhone and has a 10,000 mAh battery. And this is the world we’re living in now.” — Marques Brownlee, 0:02

”Silicon Can Expand to Three Times Its Volume”

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“During charging in a silicon carbon smartphone battery, the silicon heats up and absorbs lithium ions. And when that happens, the silicon can expand to three times its original volume. So that’s kind of insane.” — Marques Brownlee, 4:00

”A Literal Steel Cage Around the Battery”

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“I’ve actually been told there are certain devices that have a literal steel cage around the battery to prevent it from swelling.” — Marques Brownlee, 5:10

”One in 250,000 Might Not Be Good Enough”

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“Getting issues down to a rate of under one in 250,000 feels pretty good. But at Samsung or Apple’s scale, if it’s tens of millions of phones, that could still not be good enough. That could still be a dozen exploding Note 7s like it was in 2016.” — Marques Brownlee, 6:12

”People Just Want the Blue Bubbles”

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“The US especially is a very software focused market. There’s all this ecosystem lock in and inherently less hardware competition. People just want the blue bubbles at this point.” — Marques Brownlee, 7:13

Key Points

• Honor Power 2 (0:02) - iPhone clone that is thinner but has a 10,000 mAh battery vs iPhone’s 5,000 mAh
• Silicon Carbon Technology (0:28) - New battery tech enabling massive capacities without thicker phones
• Ultra Thin Phones (0:41) - Perfect for thin form factors like Galaxy S25 Edge and iPhone Air, but neither uses it
• Big Companies Sitting Out (1:00) - Samsung, Apple, and Google all avoiding silicon carbon
• How It Works (1:20) - Swaps graphite for silicon which holds way more energy; higher energy density
• OnePlus Battery Jumps (1:41) - Went from 5,400 to 6,000 to 7,300 mAh in one year using silicon carbon
• Supply Theory Debunked (2:16) - Theory that large companies can’t get enough supply, but Xiaomi ships millions with silicon carbon
• Industry Sources (2:57) - Multiple insiders from smartphone companies independently reached out about swelling concerns
• Thermal Expansion (3:32) - Batteries expand and contract during charging like any material with heat
• 3x Volume Expansion (4:00) - Silicon expands to three times its original volume when absorbing lithium ions
• Sponge Analogy (4:12) - Like a sponge tripling in size when wet, then shrinking, over and over
• Finely Ground Silicon (4:35) - Silicon is ground fine (not solid block) and carbon absorbs expansion
• Steel Cage (5:10) - Some devices use literal steel cages around batteries to prevent swelling
• Thermal Runaway Risk (5:27) - Worst case scenario from internal battery damage
• 1,000 Cycle Testing (5:32) - Companies test 80% capacity after 1,000 cycles but real world has many more variables
• One in 250,000 Error Rate (6:12) - Feels safe but at tens of millions of phones could still mean dozens of failures
• Galaxy Note 7 Reference (6:41) - Similar to the exploding Note 7 disaster of 2016
• US Software Market (7:13) - US has ecosystem lock-in and less hardware competition; no pressure to adopt risky tech
• WhatsApp Markets (7:37) - In markets using WhatsApp instead of iMessage, hardware competition drives silicon carbon adoption
• Bleeding Edge in 2026 (7:57) - Silicon carbon still bleeding edge; first phones with it came out about 3 years ago

Mentions

Companies

• Apple (1:00) - Not using silicon carbon in iPhones
• Samsung (1:00) - Not using silicon carbon in Galaxy phones
• Google (1:00) - Not using silicon carbon in Pixel phones
• OnePlus (1:41) - Early adopter, jumped from 5,400 to 7,300 mAh
• Xiaomi (2:37) - Major company using silicon carbon in all flagships
• Realme (2:41) - Using silicon carbon batteries
• Honor (0:10) - Maker of the Power 2 with 10,000 mAh silicon carbon battery
• Oppo (2:43) - Using silicon carbon batteries
• Huawei (2:43) - Using silicon carbon batteries

Products & Technologies

• iPhone 17 Pro Max (0:02) - Compared as having only 5,000 mAh without silicon carbon
• Honor Power 2 (0:10) - 10,000 mAh phone thinner than iPhone, silicon carbon battery
• Galaxy S25 Edge (0:45) - Ultra thin phone that could benefit from silicon carbon but doesn’t use it
• iPhone Air (0:45) - Ultra thin phone without silicon carbon
• Silicon Carbon Battery (0:28) - New battery tech using silicon instead of graphite for higher energy density
• Lithium-Ion Battery (6:55) - Traditional battery tech that remains the safe bet
• Galaxy Note 7 (6:41) - Infamous 2016 Samsung phone with exploding batteries

People

• Marques Brownlee (MKBHD) (0:02) - Presenter and investigator

Surprising Quotes

“The silicon can expand to three times its original volume. So that’s kind of insane. Like imagine a sponge that triples in size when wet and then shrinks back down and then over and over again every time it charges and discharges.” — 4:07

“I’ve actually been told there are certain devices that have a literal steel cage around the battery to prevent it from swelling.” — 5:10

“At Samsung or Apple’s scale, if it’s tens of millions of phones, that could still not be good enough. That could still be a dozen exploding Note 7s like it was in 2016.” — 6:34

“People just want the blue bubbles at this point. So, if people aren’t going to buy the new iPhone because of a silicon carbon battery or they’re not switching off of the iPhone because of some other phone’s silicon carbon battery, then there is no reason for Apple to take that risk yet.” — 7:21

“Fun fact, water is one of the only materials that actually expands while cooling, but it expands about 10% in volume while freezing. And if that happens too fast, it cracks.” — 3:49

Transcript

0:02 So, this is an iPhone 17 Pro Max. It has about a 5,000 mAh battery, but this is the Honor Power 2. Yes, it’s absolutely a clone of the iPhone, but it’s also thinner than the iPhone and has a 10,000 mAh battery. And this is the world we’re living in now. There are many phones out now with absolutely massive batteries the size that we only used to see in power banks, but without actually making the phones any thicker, all thanks to a new battery technology called silicon carbon.

0:33 So, if you’re a subscriber, then you’ve already heard me talk a lot, especially in the past year, about silicon carbon batteries and how great they are and how they’re even perfect for certain form factors of phones, like enabling the ultra thin ones like Galaxy S25 Edge and iPhone Air because they could be super super thin, but still with silicon carbon have normal battery capacities. But yet, those phones didn’t have silicon carbon.

0:54 In fact, a lot of phones, competitive flagship phones, have come out lately that have skipped the silicon carbon battery. It seems like whole companies like Samsung and Apple and Google are just waiting on the sidelines and not touching this new battery tech in any of their phones. And I finally think I know why. So, let’s talk about these new smartphone batteries.

1:20 So, like I said, on the surface, on the surface, it would seem like silicon carbon is a no-brainer. Obviously, you should have it in your phone, especially if you’re just looking at the benefits. They’re called silicon carbon because they essentially swap out graphite and use silicon, which can hold way more energy than graphite. So, the main advantage is higher energy density. We have phones now with way bigger battery capacities in the same footprint as always.

1:41 I remember when the new OnePlus flagship came out last January, and it made this huge jump from 5,400 mAh straight to 6,000 mAh by going with silicon carbon. And then later the same year they went to 7,300 milliamp hours. So it just felt like we are resetting what to expect from a smartphone battery.

2:00 But of course, like I mentioned, new Samsung phones keep coming out, no silicon carbon batteries. New iPhones have been coming out, no silicon carbon. Even new Pixel phones, same thing. And so people of course are talking about it. Now, I’d had some suspicions about why, and a couple other YouTubers have also shared, but I think the main theory was that these are huge companies that are going to ask for massive quantities of stuff from suppliers.

2:22 So, with a brand new tech like silicon carbon, you know, if you’re Apple, you’re going and asking for 10 million of these things for your new iPhone. And maybe that wasn’t possible yet. So, understandable if that’s true. But then again, Xiaomi is huge and they’re using silicon carbon in all their flagships and Realme and Honor and Oppo and Huawei and all these companies using tons of silicon carbon in a lot of volume of phones.

2:48 Meanwhile, Google’s over here with the Pixel not shipping that many phones and not using silicon carbon. So maybe that’s not the whole story. So then I recalled I’ve gotten a few emails in the past year from people in the industry and I won’t say which companies they work for but all smartphone companies and individually they’d each reached out to me to mention that there are some concerns with silicon carbon batteries and all their stories matched up about a totally different concern about swelling and longevity.

3:18 Now I had only seen that in these emails. So, I went digging and I reached out to a couple other sources and people that I know at these companies. And now that I’ve heard back from them, I’m actually much more confident that this is the main reason that we’re not seeing this tech everywhere in a ton of phones.

3:32 See, one thing about batteries is that as they charge and discharge, they expand and contract a little bit with the heat, just like almost any other material. It’s why sidewalks have cracks. It’s why bridges have expansion joints. Basically, every material has to expand and contract a little bit with heat, right? Fun fact, water is one of the only materials that actually expands while cooling, but it expands about 10% in volume while freezing. And if that happens too fast, it cracks.

4:00 So during charging in a silicon carbon smartphone battery, the silicon heats up and absorbs lithium ions. And when that happens, the silicon can expand to three times its original volume. So that’s kind of insane. Like imagine a sponge that triples in size when wet and then shrinks back down and then over and over again every time it charges and discharges. Eventually things are probably going to crack.

4:21 You know that meme going around where it’s like, “Oh, if you want to clean the ice off your car windshield really fast, just pour boiling water on it.” But obviously you shouldn’t do that because that could literally shatter your windshield because of rapid temperature change thermodynamics.

4:35 So in the battery, the silicon is actually really finely ground instead of a solid block to avoid the mechanical stresses and the carbon is actually there just to absorb the expansion. So that’s why it’s called silicon carbon. So everyone’s messing around and trying to tune it. Some companies are willing to include a higher and higher percentage of silicon because that lets you get a higher and higher battery capacity in the same space, but that’s also pushing the limits.

5:02 And so they also have to do their best to manage the inevitable swelling to counteract that. It’s just physics or chemistry. I’ve actually been told there are certain devices that have a literal steel cage around the battery to prevent it from swelling. And then the cracking in this case is potentially some type of internal damage to the battery, which is obviously really bad news. And worst case scenario is some type of thermal runaway, which obviously nobody wants that happening in their pocket.

5:30 And so you might be thinking, oh, what about all the testing? Like that’s one of the most common things we hear from these companies is they’re always able to verify something like, you know, 80% battery capacity after a thousand charge cycles. So trying to give us some confidence in the longevity of these batteries because they’ve actually tested that many cycles. Like that should make it survive years of regular use.

5:51 But batteries obviously go through a lot more in regular use than just charge cycles. Like they deal with a lot of outside heat and cold. They get dropped sometimes. There’s pressure changes, there’s humidity changes, etc., etc. It’s a long list. So, testing is really important, of course, but it’s really hard to account for all the variables that a battery might experience over a long period of time.

6:12 In one of my conversations, my source mentions that with all the thorough testing going on, getting issues down to a rate of under one in 250,000 feels pretty good. Like if you have an error rate of something that’s under one in 250,000, that’s a very rare issue and you should be good to go. But at Samsung or Apple’s scale, if it’s tens of millions of phones, that could still not be good enough. That could still be a dozen exploding Note 7s like it was in 2016.

6:46 So since there isn’t quite enough real world data yet, especially over longer periods of time, some companies are choosing to just sit it out for now and continue developing regular lithium-ion batteries. And you know, remember those companies I mentioned at the beginning that are all not using silicon carbon, the Samsungs, the Apples, the Googles, they’re all huge companies, but there’s also something else they all have in common, which is they all operate or at least have a big presence in America.

7:13 And I bring this up because we’ve talked about this before. The US especially is a very software focused market. There’s all this ecosystem lock in and inherently less hardware competition. People just want the blue bubbles at this point. So, if people aren’t going to buy the new iPhone because of a silicon carbon battery or they’re not switching off of the iPhone because of some other phone’s silicon carbon battery, then there is no reason for Apple to take that risk yet.

7:37 But in other markets where people can just use WhatsApp and be happy about it, then there’s way more hardware competition and people are willing to switch. So if one phone has a 40% bigger battery because of some new emerging technology and the other one feels like they’re being left behind, people will move to that.

7:54 So yeah, this will be fascinating to watch it play out. You know, today still in 2026, silicon carbon batteries are still a bleeding edge technology. They’re still a little bit riskier and lithium-ion batteries are still the safe bet. But there’s this divide now. So, we’ll have to keep an eye on how these silicon carbon phones actually age. You know, the first ones came out about 3 years ago, but there’s been a lot more out in the real world in the past year. And so, we’ll check in.

8:20 Get subscribed, and maybe in a year or two, we’ll have a lot more real world data. We’ll check in. We’ll see how things are going. Thanks for watching. Catch you in the next one. Peace.