An Australian woman on a flight from Beijing to Melbourne was listening to music on her battery operated headphones and had gone to sleep. On the way, the passenger heard a loud explosion, and woke up to the headphones burning in her ear. She said “As I went to turn around I felt burning on my face. I just grabbed my face which caused the headphones to go around my neck. I continued to feel burning (sensation) so I grabbed them off and threw them on the floor. They were sparking and had small amounts of fire.”
The incident caused the Australian Transport Safety Bureau to issue a warning, that consumer electronics with batteries should be stored in approved stowage when not in use, that such electronics are only allowed to be transported in the checked in baggage (but are allowed on the carry on baggage), and instructions on making sure that a device is removed from seat gaps before the seats are moved.
Late last year, Samsung was forced to execute the largest consumer electronics recall in history because of a potential fire and burn hazard. The Samsung Galaxy Note 7 devices had the tendency to spontaneously combust, and the problem was traced to the lithium ion batteries on the device, and the way it was packed in. Replacing the devices did not stop the explosions, and Samsung had to discontinue the model. As a safety precaution, Samsung rolled out a software update that prevented Galaxy Note 7 batteries from charging up and being functional.
The spate of battery explosions highlight the limitations of Lithium ion batteries in consumer electronics. Although in use for many years, the energy released from the batteries can cause explosions if it is not adequately controlled. The batteries are susceptible to explosion on being punctured, on experiencing too much pressure and on being charged to quickly. There are usually safety precautions in place to prevent explosions caused by these reasons, but in the push for smaller devices, some of these safety precautions may be compromised.
Usually, there are vents around a battery to prevent build up of excess heat. Room for expansion is left around the batteries as well, to accommodate the natural expansion and contraction experienced by batteries during the charge and discharge cycle. Fail-safe circuitry prevents too much charge being delivered to the batteries. Lithium is preferred despite its volatility because of how light it is and how much energy it can provide. Lithium Ion batteries have reached almost the limits of their theoretical capacities in consumer electronics, and manufacturers going for more battery life and smaller devices tend to cut corners when it comes to safety precautions.
Lithium ion batteries are made up of two electrodes, an anode and a cathode, and an electrolyte. The negative and positive electrodes should never touch each other, or the resulting short circuit will cause the battery to explode. Samsung apparently made the batteries too large, and did not leave room for expansion. The curved edges meant that the opposite electrodes within the batteries bent and touched each other. Exposure to excessive heat is another reason that causes Lithium ion batteries to explode. Exposure of the internals of a Lithium ion battery to moisture also causes explosions. Atmospheric moisture is the reason Lithium ion batteries explode on being punctured.
There are many efforts around the world in developing safer alternatives to Lithium ion batteries. Researchers at ETH Zurich in Switzerland are investigating solid electrolytes instead of liquid ones, that are less volatile. The solid electrolyte batteries do not explode on being overheated, or exposed to the air.
Researchers at Stanford university have used Artificial Intelligence to identify over twenty candidate materials for a solid electrolyte to be used in safer Lithium ion batteries. Stanford researchers have also developed an approach that introduces a flame retardant in the battery itself, preventing the batteries from exploding. Tufts University researchers are also working with solid electrolytes.
Looking at the regularity with which Lithium-ion batteries are exploding not just in phones, but also washing machines and now battery powered headphones, it is about time device makers took battery safety a lot more seriously.
Publish date: March 16, 2017 10:39 am| Modified date: March 16, 2017 10:50 am