Lithium ion batteries are in all sort of tech these days, from your phone and laptop to aeroplanes and electric vehicles. But a voluntary recall of some 2.5 million Samsung Galaxy Note 7 smartphones after reports of battery explosions has raised new concerns about their safety.
Aviation authorities and airlines from North America to Europe and Asia have issued bans or guidance on the phones. The US Consumer Product Safety Commission advised consumers “to stop charging or using the device”.
In Hong Kong, the Consumer Council warned people to stop using the Note 7 immediately. Samsung said its replacement programme in Hong Kong and Macau only applied to Note 7s bought before September 2, since models sold through authoristed outlets on or after that date use batteries from a different supplier to the ones at risk of exploding.
Here’s what you need to know about the lithium batteries that probably power most, if not all, of your electronic gear – and why they sometimes catch fire.
What are lithium ion batteries, and why are they so popular?
Lithium ion batteries are a bit different from the basic AAs you use to power your TV remote. They’re rechargeable, often built directly into devices and rely on the chemical lithium as their primary fuel.
Lithium ion batteries are especially popular in devices such as laptop computers and phones, because they store energy so efficiently and are slow to lose their charge.
“You get a lot of oomph relative to older technologies that were the same size – often two to four times the voltage,” explains Stephen Hackney, a professor of materials science and engineering at Michigan Tech University.
How do they work?
Like most batteries, lithium ion batteries work by storing energy and releasing it through controlled chemical reactions.
A lithium ion battery has two electrodes – places where electricity can enter or leave the battery – on opposite sides.
One electrode, called the anode, is filled with negatively charged ions. The other electrode, called a cathode, contains positively charged ions and lithium. You can think of the anode and the cathodes as the plus and minus signs on AA batteries.
When you use a battery, the lithium moves from the cathode to the anode – and when you charge it, the lithium moves back to the cathode. There’s a separator inside that keeps the anode and the cathode from touching because that can trigger mishaps such as fires and explosions.
What can cause the explosions?
The reason you can shove so much power into lithium ion batteries is that lithium “wants to react with almost anything” – which can lead to explosive results, Hackney says. But one of the most common reasons the batteries explode is because of mistakes in the charging process, he adds.
Inside the devices that rely on the batteries there is software that tells them exactly how much the batteries should be charged and how fast. If those protocols are set incorrectly, it can destabilise some chemicals inside the battery and cause a chain reaction that researchers call a “thermal runaway” that may lead to fire or an explosion.
Overheating can also cause an explosion, which is why your phone probably pops up with an alert about needing to cool down when it gets too hot.
Another reason could be shoddy manufacturing or rough user treatment. If unwanted materials, like scraps of metal, accidentally end up inside the battery when it’s being made, they can short a cell of the battery and set off a thermal runaway.
Dropping a device could also cause problems if the impact causes a break in the separator between the anode and cathode.
What happened with the Galaxy Note 7?
It seems like a manufacturing problem. The company reports at least 35 cases where the batteries combusted due to “a very rare manufacturing process error” in which the anode and cathode touched.
Samsung decided to temporarily pull the phone off the market two weeks after it was released and is offering replacements to people who already purchased the device.
How often do these problems occur?
The good news, according to Hackney, is they’re pretty uncommon, especially among high-end devices, when manufacturers keep a close eye on production quality.
But there have been plenty of high-profile cases. For instance, 2006 Dell recalled more than four million laptop battery packs over combustion issues. In 2013, the Boeing 787 Dreamliner was grounded by the US Federal Aviation Authority after reports of fires related to the lithium ion batteries used in the planes. And half a million hoverboards were recalled this summer because of lithium ion battery explosions. iPhones have also caught fire before.
Are regulators looking into these batteries?
The government and international organisations already regulate lithium ion batteries in a lot of ways, which is probably one of the reasons we don’t see more explosions. For example, the US Department of Transportation has rules for how to safely ship the batteries.
Other US regulations also call for batteries that end up in consumer goods to go through various safety tests, and the Consumer Product Safety Commission has overseen a lot of recalls involving products with lithium ion batteries that were deemed hazardous. The agency is working with Samsung on a formal Galaxy Note 7 recall in the United States.