“You won’t believe what happened last night,” my friend said as we approached our gym lockers, unloading our shoulders of our purses and totes stuffed with changes of clothes.
“What?” I asked absently, wedging my belongings into the small metal box.
By way of an answer, she thrust her iPod in my direction—a piece of equipment that was certainly a more constant gym companion to her than I. As I took the thin device in my hand, I registered for the first time that its once chrome exterior was slightly marred on the back, as if it had been charred.
“I took it off the charger this morning, and it was hot. Now it won’t turn on,” she explained.
This instance, while perhaps surprising, isn’t so uncommon. Some evidence would suggest, in fact, that my friend was lucky that her iPod didn’t go up in honest-to-god flames instead of dying quietly in the night.
As technology has become increasingly accessible and manufactured on a massive, global scale, allowances have been made for innovation which favors certain qualities: make it smaller, lighter, and more powerful. Whether it’s a vehicle, a phone or a toy—with the proliferation of personal, high-tech electronics we have seen a sometimes funny, often baffling, but always fiery trend: spontaneous combustion.
Spontaneous combustion, loosely defined, happens when an object begins to heat itself from the inside out. The object increases in temperature without drawing any heat from its surroundings until, bam!—it’s smoking, and then burning in your living room, in your garage or your pocket.
Different Devices, Same Fires
iPhones, hoverboards, e-cigarettes, iPods, Boeing 787s. That’s a shortlist of electronics, vehicles and other devices that have unexpectedly caught fire, some more prominently—and more frequently—than others. While Samsung’s Note 7 debacle is on the forefront of our minds when we hear the phrase “spontaneous combustion,” they are certainly not the only business that has had to smother the flames to save their reputation.
Standing rank and file behind the Note 7 as the most commonly malfunctioning device is the e-cigarette. Since 2009, more than 25 reports of e-cigarettes spontaneously combusting have been reported in the United States, making these incidents relatively rare, but certainly not without consequence. Many of these reports go on to elaborate the consequences—usually thermal, blast and alkali burns sustained to the thighs, the buttocks and surrounding areas—that require surgery (people carry these in their pockets, obviously). Imagine the horror of, with little warning, finding your pants on fire, as one man did per a report from the Santa Clara Valley Medical Center. The victim’s e-cigarette “spontaneously combusted while [he was] shopping in public. His pants caught fire and were immediately removed to extinguish the flames.” If you think that embarrassing, consider staking your reputation on building vehicles that safely ferry passengers through the skies, only to have your airplane catch fire.
Such was the case for one Boeing 787 Dreamliner as it cut its initial path out of Boston in early 2013. Almost instantly after takeoff, a member of the cleaning crew noticed smoke near the rear of the cabin. The crew immediately grounded the airplane, at which time mechanics opened the back equipment bay to find smoke and flames billowing out. It took nearly two hours for ground crews to control the fire, which seemed to be fed by something leaking from the airplane’s power unit. This particular airplane, while relatively new to the airline’s fleet, definitely wasn’t on its maiden voyage. It had, in fact, made 22 separate voyages before the battery unit failed. Just five days later, another 787 made an emergency landing in Japan after pilots received a battery malfunction warning. These distinct incidents led to Boeing fleets throughout the world being grounded while investigators began to look for the root cause of the problem.
Boeing’s troubles with combustion highlight concerns about the use of new and potentially dangerous technology onboard commercial aircrafts and in the electronics we use everyday. What’s at the heart of Boeing’s particular problem is actually what’s at the core of most instances of devices spontaneously combusting: lithium ion batteries.
The Cause of Spontaneous Combustion
Lithium batteries have become practically indispensable to our existence in the 21st century—they allow us to post on Instagram and snap digital photos, to ease nicotine cravings with e-cigarettes or use a cordless drill, travel by airplane and electric car, or even explore Mars with rovers like NASA’s Curiosity. Yet all that they offer comes at an occasional cost. These batteries—tiny, lightweight and powerful—pack a huge punch in a small package, making them volatile, with an energy density of up to around 160 watt hours per kilogram; that’s roughly twice that of a regular alkaline battery.
Despite hoverboards which have exploded while plugged in to charge, and iPhones that have lit yet another pair of pants on fire, the incidences of spontaneous combustion remain minimal compared to the number of lithium batteries being used at any given moment. The laptop I’m typing on is powered by a lithium ion battery. My cell phone, currently plugged into its charger on the nightstand, is also powered by such a unit. Even the Curiosity Rover that has been tooling around outer space for six years sports a rechargeable lithium battery, and not one of these things has yet caught fire.
What’s at the core of all these cases of spontaneous combustion is an ideal that we as a species tend to pride ourselves on: innovation. As engineers pack more power into increasingly smaller battery units, the separator between two delicate components of the battery has become thinner and favors the least dense metallic element, making the overall package more efficient and versatile, but also sometimes more dangerous. In a lithium ion battery, the positively-charged cathode and the negatively charged anode must be physically separated to prevent a dramatic reaction that results in—you guessed it—spontaneous combustion. A liquid electrolyte, which contains lithium, allows an electric charge to move back and forth between the two sides, effectively creating power. In the event that the separator between the two sides of the battery is breached (AKA: a short circuit), a thermal runway is created, and the chemicals inside the battery begin to heat up rapidly, and can even reach a scorching 1,000 degrees Fahrenheit. At this point, if exposed to oxygen, the flammable lithium electrolyte solution can ignite and even explode.
While this may seem a bit frightening, rest assured that your hoverboard is more likely to kill you while you attempt to use it as the manufacturers intended rather than while you charge it. All in all, there have only been 43 distinct recalls of lithium ion batteries since 2002, yet hundreds of millions of these workhorses have been manufactured in that same time. As the scourge of combustion continues for lithium batteries, there has been an increased push toward improving their safety without sacrificing any of their power.
Engineers at manufacturers worldwide are developing more rugged polymer separators which sport a higher melting point should a thermal runway be created, and many are also testing electrolyte solutions that don’t catch fire when exposed to oxygen. These improvements alone would reduce the likelihood of spontaneous combustion among our most beloved devices at least tenfold.
As we look to the future of battery-powered energy, we can anticipate more spontaneous combustion, but must acknowledge it as a necessary learning opportunity as we continue to innovate with the help of technology (and send Snapchats, puff e-cigarettes and mess around on hoverboards, too).