The lithium-ion battery that didn't explode

A new invention could solve battery fires. We test it out by blowing things up -- for science, of course.

Sean Hollister Senior Editor / Reviews
When his parents denied him a Super NES, he got mad. When they traded a prize Sega Genesis for a 2400 baud modem, he got even. Years of Internet shareware, eBay'd possessions and video game testing jobs after that, he joined Engadget. He helped found The Verge, and later served as Gizmodo's reviews editor. When he's not madly testing laptops, apps, virtual reality experiences, and whatever new gadget will supposedly change the world, he likes to kick back with some games, a good Nerf blaster, and a bottle of Tejava.
Sean Hollister
11 min read

Batteries are our lifeblood. Lithium-ion power cells, first commercialized by Sony in 1991, enable nearly every 21st century convenience: Phones, laptops, wireless headphones, cordless power tools -- even electric vehicles.

But like the other great conveniences of our modern age -- automobiles and air travel -- on the rare occasions lithium batteries go wrong, they can go catastrophically wrong. 

Just ask the family of Nazrin Hassan, the Malaysian tech incubator CEO who died after one of his phones burst into flame. Consider Tallmadge D'Elia, who expired when his exploding vape pen sent fragments into his skull. Or think of the hoverboard owners who watched their houses burn down.


A New York man filed a lawsuit after his Swagway hoverboard exploded while charging.

Chappaqua Fire Department

You're far more likely to be struck by lightning (1 in 1,042,000) than ever see a battery flame up (1 in 10 million is the number experts tend to quote). But the fact remains: Like your car's gasoline engine, lithium-ion batteries require flammable liquids to generate their power in a controlled chemical reaction. 

If that reaction gets out of control because the battery's structural integrity is breached -- or if there's a widespread manufacturing defect like one that afflicted 2016's Samsung's Galaxy Note 7 -- all bets are off. That's why, even as we surround ourselves with more lithium-ion-powered devices, we don't fully trust them yet.

But what if that fraction of a doubt could be removed? What if the safety profile of lithium-ion batteries could be made to be so reliable that even a catastrophic structural failure -- up to and including being pierced by a bullet -- wouldn't cause them to explode?

That's exactly the promise of SafeCore, by a company called Amionx. The tiny California firm claims it's created a lithium-ion battery that won't catch fire even if crushed, shot or otherwise breached.

CNET flew to Amionx's Carlsbad facilities earlier this year, where we submitted SafeCore batteries -- and some normal lithium-ion competitors -- to a full range of torture tests. You'll want to watch our video below. 

Spoiler alert: When we stabbed, shot and smashed the "brand X" batteries, they burst into beautiful, brilliant, scary flame. But under identical conditions, the SafeCore batteries didn't catch fire.

According to Amionx, the company's breakthrough isn't just a battery that doesn't easily combust. It's that the company's scientists discovered a formula they claim could easily be applied to existing battery manufacturing lines -- no new machines required -- to bring this breakthrough to any lithium-ion battery in the world.

They claim the invention could take those batteries places they've never been safe enough to go before.

How? Amionx has a secret sauce. Literally.

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Amionx shares a building with its parent company, American Lithium Energy.  


The invention

A palm-tree laden Carlsbad business park just past Legoland California may not be where you'd think to find the next leap in battery safety. But walk through a special door past the normal business trappings -- the vacant receptionist's desk, the cubicles and conference rooms -- and you step onto a miniature factory floor with its own lithium-ion battery assembly line.

The company says these machines can produce a million lithium-ion battery cells per year, and they're not just here for show: American Lithium Energy, the parent company of Amionx with which it shares the building, supplies batteries to the US military for use in heavy-duty trucks and lightly armored vehicles like the MRAP, among other projects. (Public records show the company has received $2.77 million in R&D grants from the Army to date.)

Sean Hollister/CNET

Today, the humming machines are being used to show what Amionx's secret sauce can do. One spoonful at a time, a technician drizzles the black goop onto a thin sheet of metal winding through the machine from reel to giant reel. This particular apparatus is an electrode laminator, which coats the battery's all-important positive and negative terminals in an array of chemicals before they get sliced into smaller pieces and stacked (or wound) into a complete battery cell.

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What we're seeing seems to be a typical, ordinary battery making process, goop and all -- but Amionx's compound is a special formula that took four years to create.

When a battery heats up, threatening to catch fire, Amionx's special material acts like an electrical fuse, creating a physical gap between two key components of the battery. That gap means electricity is forced to take a far more difficult path through the cell, which dramatically slows down the reaction to the point a battery doesn't get hot enough to catch fire or explode.

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An electrode stacking machine constructs a pouch-style Lithium-ion battery cell.


It's not like there aren't other ways to protect a battery. Amionx founder and CTO Dr. Jiang Fan admits that today's lithium-ion batteries have a variety of other mechanisms that can prevent fires, including current interrupters, shutdown separators and PTC (positive temperature coefficient) devices, but he says all of them can fail -- a battery can heat up so fast that some safety mechanisms may literally melt before they can take action.

"That's why sometimes even though they have the shutdown separator for 20 years, they still have these thermal incidents," says Fan -- adding that his SafeCore kicks in right away.

The test

To test out Amionx's safety promise, we open another door at the back of the factory floor, and walk outside into a fenced area of the building's parking lot -- where industrial-strength battery crushing and puncturing test chambers are waiting to let the smoke out of these cells. One machine is designed to drop a huge, heavy weight onto a metal bar laid flat across the top of the battery, completely crushing a large portion of a battery in an instant, while the other slowly punctures it with a giant nail.

The competition: Here's what happens when you puncture a non-SafeCore lithium-ion battery.


While our camera crew takes a moment to set up a super-slow-motion shot, I quietly crouch down next to a pile of ready-to-test batteries and whip out my multimeter to verify the current. But sure enough, the meter reads 4.2 volts -- we're looking at fully charged lithium-ions.

Then, we play NASA Mission Control, counting down to the moment our technician will press the big button and these batteries will get their chance to ignite.

First, we try a standard lithium-ion pouch battery pack -- no SafeCore material inside. As the nail goes in, it's astounding how quickly the battery reacts. It bulges like a balloon, bursts with a puff of smoke, shoots out flying reddish sparks and finally explodes into a huge column of flame that reaches the ceiling of the test chamber -- all within 6 seconds flat.


The grisly charred remains of a standard lithium-ion pouch cell, after the puncture test.

Sean Hollister/CNET

With the crushing machine, the same reaction takes just 3 seconds. (Dr. Fan says that's because the wider crush zone means we're shorting out the battery more thoroughly.)

But when we place SafeCore-treated batteries in the same torture devices, there's no bulge, no smoke, no flame. The punctured, crushed batteries are warm, maybe even hot to the touch for the next 10 minutes, but they feel no more dangerous than the hand warmers my Scoutmaster used to hand out on Boy Scout camping trips.

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Logan Moy/CNET

A couple of hours later, we test the company's most extreme claim at the Pala Shooting Range, located on the Pala Indian Reservation some 30 miles northeast of Amionx HQ. With a short, sharp crack, an expert rifleman puts a .223 round through each battery with precision -- just after our camera crew lines up their shot and scrambles to safety.


For the regular lithium-ion battery, the shot is unsurprisingly fatal. The cell puffs up, melts through its plastic housing, falls to the ground and bursts into flame.

The SafeCore battery? The bullet rips it a new one, but it doesn't budge an inch.

One caveat: While the SafeCore batteries might be able to take a bullet, Amionx's Bill Davidson says they can only take one bullet safely. Remember, there's still inherently a flammable liquid inside these batteries, and now it's leaking out of a bullet hole… a second shot could cause a spark and start a fire, Davidson warns.

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Yep, that's CNET's Ashley Esqueda holding a punctured Safecore battery with her bare hands.


The possibilities

Amionx is dreaming big. Originally developed to try to satisfy a US Army request for bulletproof "conformal" batteries that infantry soldiers wear to power their electronic gear, the company now imagines every new battery could potentially use SafeCore to reduce the chances of an incident -- and that the protection could open up new avenues for the tech.

For instance, the company thinks SafeCore could also dramatically extend the range of electric vehicles -- because 50 to 70 percent of the weight of an EV battery is tied up in the containers that manufacturers use to keep those batteries safe, according to the company.


The US Army's conformal batteries were designed to fit inside a tactical vest, instead of requiring separate pouches.

US Army Photo/Conrad Johnson, RDECOM

If it turns out that SafeCore is adequate protection, EV builders could theoretically throw out those other protections to fit more power cells inside. (Less weight to haul around also helps vehicular range.)

Laptops could theoretically go longer on a charge, too, with larger capacity batteries than ever before, should the powers that be approve. Did you know it's illegal to carry a laptop on an airplane with a battery capacity greater than 100 watt-hours? That's been the rule in many countries (including the US) for a number of years now, and laptop batteries like the one in the Dell XPS 15 are already pushing the limit. Amionx says it's already talking to the FAA.

The company even sees its batteries potentially being safe to implant inside the human body (say, pacemakers) -- a place where even the tiniest risk of a flaming battery is unacceptable.

Dr. Fan doesn't necessarily expect all of this to happen right away. He imagines battery makers won't trust SafeCore to be the only battery safety mechanism anytime soon, for example. But he says leading battery makers could be up and running with SafeCore in under six months, as soon as they're ready to license his secret formula.

When that will happen, however, is anybody's guess.

The hesitation

As our video attests, SafeCore gives a great demo. And that success seems to stand up to third-party testing, too. Noted product testing firm Underwriters Laboratories (UL) has tested some of the SafeCore batteries and found them to demonstrate similar results. (The batteries aren't necessarily UL safety certified yet; the lab was merely confirming, at Amionx's request, that they performed as advertised.)

But that successful performance raises a key question: If SafeCore is so clearly the next big thing in battery technology, why isn't it already the next big thing in battery technology? Why isn't the industry falling over itself to incorporate SafeCore's process?

One potential issue is that classic Silicon Valley challenge: Can it scale? That's the question posed by Professor John Goodenough, the battery pioneer whose groundbreaking work in the 1970s and 1980s led to the development of the lithium-ion battery to begin with. 

He suggests it's possible that a laminate like SafeCore might not always be reliable when mass-produced. "It would need time to separate faster than the time to ignite the liquid electrolyte. Given the limited space in a cell, I wouldn't trust this to work in every cell made," he wrote by email.

Isidor Buchmann, founder of educational site BatteryUniversity.com, basically agrees. Buchmann says that in tightly wound cylindrical battery cells like the common 18650 -- basically, a super-powerful, oversized AA battery that's utilized in power tools, laptops, USB battery packs and even Tesla cars -- there might not be space for SafeCore to create a big enough gap. 

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18650 Li-ion batteries are the building blocks of many larger battery packs. From left to right: a 14500 Li-ion, a standard rechargeable AA battery, a 18650 Li-ion and a portable USB battery that contains multiple 18650 cells.

Sean Hollister/CNET

Buchmann said that over the years, he's seen a variety of convincing demos of batteries that were little better than magic tricks since they couldn't be manufactured at scale. "I've seen shooting, puncturing and so on -- but batteries do fail," Buchmann told CNET.

Amionx COO Bill Davidson dismisses these fears, saying there's more than enough room since the SafeCore layer is only 1 to 5 microns thick -- a mere fraction of the thickness of a human hair. "We've even conducted testing where a pouch cell is literally bolted between two metal plates and tightened to not allow for any expansion of the pouch itself," says Davidson, adding that the company hasn't ever seen SafeCore fail after a given battery design has been finalized.

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A 18650-sized cylindrical battery cell, wound on Amionx's battery winding machine.

Sean Hollister/CNET

Ultimately, Goodenough and Buchmann are basically saying that Amionx's solution is challenging -- not impossible. But assuming the company has threaded that engineering needle, where are the customers?

Dr. Fan, the CTO, says that Amionx is in talks with five of the six biggest battery manufacturers to license the SafeCore tech. None of the major names in the battery world had anything to say about Amionx and SafeCore, however: LG Chem declined to comment, and Samsung SDI, Panasonic Sanyo, BYD and Tesla didn't respond to requests for comment. But in a tech world where product leaks and strategic partnerships are disavowed right up until the moment they're announced on stage, that doesn't mean much.  

Still, at least one tech giant has gone on the record with a big vote of confidence in SafeCore. Qualcomm, the chip giant that makes the silicon found in a huge chunk of the world's phones, invested in Amionx last year. "After performing diligence on both the IP [intellectual property] and technology, we became comfortable that Amionx Safe Core is differentiated to help deliver value to suppliers and consumers of lithium-ion batteries," said Alex Rogers, head of the company's licensing arm, in a statement to CNET.

Solid competition on deck

Even if SafeCore turns out to be far safer than traditional lithium-ion batteries, there's a chance manufacturers will hold out -- if they see it as an unnecessary, expensive stopgap until a new, safer kind of battery comes along. Researchers are currently working on batteries that replace that oh-so-flammable liquid electrolyte with water or even a solid polymer material.

Those so-called solid-state batteries are what battery pioneer Goodenough is currently working on, and it's where a whole bunch of electric car companies are placing big bets -- BMW, Volkswagen, Toyota, Honda and Nissan are investing in the tech, even if not every auto exec thinks they'll be ready anytime soon.

Amionx says the costs of SafeCore are minimal -- just a licensing fee, inexpensive chemicals that companies can obtain themselves, and maybe the electrode laminator needs to run 20 percent longer to apply the SafeCore layer properly. And Amionx says its invention could theoretically improve solid-state batteries by protecting against overcharging, something solid-state batteries aren't immune to.

There's also the cost factor. The reality, according to Dr. Fan, is that battery companies do calculate how big a potential loss they can sustain, balancing the liability risks of a rare fire against the cost of changing up their batteries. Given the razor-thin profit margin of the consumer electronics industry, companies are likely investing in product improvements that are higher on customers' wishlists: making batteries that last longer, weigh less and charge faster, to name just a few.

But Samsung's Galaxy Note 7 crisis in 2016 shows us what happens when the possibility of a battery fire edges past its normal 0.00001 percent chance. Should another such incident result in injury or even death, it could have huge repercussions for the companies involved and the industry as a whole.

So for now, Amionx CEO Jenna King is pitching SafeCore as a form of insurance against that possibility:

"If it isn't going to cost me a lot to put it in there, but it's going to cause me to not have a loss of life…when you look at that risk/benefit profile, I think this technology makes sense to ultimately appear in every lithium battery in the world."

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