If you do a quick scan of the baggage policies of the major international airlines, one fact will quickly become apparent: batteries can be hazardous.
The guidelines for Emirates passengers who wish to fly with batteries or battery-powered devices run to almost 900 words, with sections related to drones, hoverboards, smart baggage, e-cigarettes and mobility aids. This abundance of caution is because of the small risk posed by the lithium-ion batteries that power the majority of consumer electronics: if they fail, or if they become damaged, there's a chance that they could catch fire or even explode.
Over the years, there have only been a handful of incidents on aircraft, all quickly dealt with by quick-thinking cabin crew – but it's a threat taken seriously by the industry. According to a report earlier this month in the American Journal of Transportation, a fire caused by a lithium-ion battery in the cargo hold of a plane could lead to a catastrophic explosion. So why have these power sources become so ubiquitous when question marks still hang over their safety? And is anything being done to eliminate that danger?
The dangers of lithium
Lithium's potential to provide rechargeable power was discovered in 1977 by a British scientist named Stan Whittingham, but he found in his early experiments that lithium cells were unstable and could catch fire. Following his discovery, however, chemists came up with ways of improving safety and performance. Different materials were tried for the electrolyte (the flammable liquid that assists the movement of ions within the battery) and the two electrodes, while various ingenious methods were tested to keep the electrodes apart and prevent them from short circuiting.
Lithium, however, has always been a critical component, and keeping that volatile element safe has become more difficult as more power has been demanded from batteries, according to Dr Allan Paterson, head of programme management at the Faraday Institution, an organisation supporting research into battery performance. “We’ve seen an evolution of lithium-ion technology to give access to improved performance,” he says, “and mitigate against the negative side of things. But the tools in the chemistry toolbox only get you so far.”
The basic components of the lithium-ion battery haven't changed since they first appeared in a consumer product (a Sony camcorder) in 1991. The electrodes are made of lithium cobalt oxide and carbon, and a thin layer of plastic keeps them apart. If, however, that separator fails and the electrodes touch, the resulting short circuit can generate intense heat, which can ignite the electrolyte.
An incident on a Qantas aircraft back in June 2016, when a phone was crushed in a reclining passenger seat and caused a fire, demonstrated how dangerous damaged batteries can prove. Those risks have grown as devices have become slimmer, with the plastic separator now as thin as six microns (more than 10 times thinner than the average human hair).
“You’re packaging more energy into a smaller space, but there are many layers of protection built in [to a battery],” Dr Paterson stresses. “The casing will be designed in a certain way, there will be electronic systems to monitor the cells. You would have to go through all those protective layers before you get to that end point of something going badly wrong.”
But things do occasionally go wrong. In September 2016, Samsung recalled 2.5 million Galaxy Note 7 smartphones after more than 100 battery-overheating incidents were reported in the US alone. This was down to faulty separators within the battery, but replacement devices that used batteries from a different supplier were also found to exhibit a similar fault. So-called hoverboards (also known as smart balance wheels) have been notorious for explosive battery defects caused by bangs and knocks sustained during their use – this has resulted in them being banned from more than 60 airlines in both carry-on and checked-in luggage. Cheap lithium-ion batteries produced on a budget have also been found to be susceptible to fire.
So what's the answer?
There may be solutions on the horizon, however. Last week, engineers from the department of mechanical engineering at the University of Michigan announced the development of a lithium-ion battery that replaces the flammable electrolyte with a solid ceramic, which not only reduces the risk of fire, but also enables a "100 per cent improvement in energy density", according to the head of the project, Jeff Sakamoto. These batteries are known as solid-state, and according to Dr Paterson, they're one of the most promising routes towards powerful, safe battery power.
“Everyone in the labs is looking at what the next generation of batteries will look like,” he says, “and using solid-state devices to avoid flammable electrolyte would give a safe and stable system. It’s at the end of all the phone manufacturer’s road maps. There’s a lot of attention on it at the moment.”
But that lab work is progressing slowly. While solid-state battery experiments using glass or plastic as the electrolyte have also yielded promising results, the arrival on the market of durable, safe and powerful batteries could be years away.
“Even for traditional chemistries,” Dr Paterson says, “it’s a tortuous route to get from lab-scale development – which is where we’re at today with solid-state batteries – all the way to full-blown manufacture. Even if you have something which works in the lab, you’ll still have several years to go before it’s ready for manufacture. And chemistries fall down on the way. They have done so, and they will do in the future.”
Some industry observers have pondered whether the manufacturers of smartphones, tablets and other lithium-ion-powered devices really want the longevity that solid-state batteries promise. After all, it suits them very well for lithium-ion batteries to degrade, prompting consumers to upgrade to a newer, more powerful model of phone. But powering those new devices won't be easy using standard lithium-ion cells – experts believe that we have pushed the limits to around 90 per cent of their physical capacity. It seems that the next generation of devices will need the work of some fiendishly clever scientists – not only to keep them powered, but also to keep the airline industry reassured of their safety.