Sometimes the solution to a problem is so obvious that it goes unnoticed.
When it comes to mitigating battery fire risks, incorporating extinguisher chemicals into the works might be an example of that, until now. Researchers from Clemson University may have eliminated the rare, but potentially cataclysmic potential for runaway battery fires.
"We wanted to develop an electrolyte that was nonflammable, would readily transfer heat away from the battery pack, could function over a wide temperature range, was very durable, and would be compatible with any battery chemistry," Clemson's Apparao Rao and Hunan University's Bingan Lu, wrote in a press release. The research team included experts from Clemson and Chinese universities.
In common lithium-ion batteries, ions move between two electrodes through a substance called an electrolyte. Liquid versions are flammable when worst-case short-circuits happen, causing temperatures to quickly rise hundreds of degrees. The findings from Clemson could eliminate that possibility, which is one of the few concerns preventing some potential electric vehicle buyers from switching to a cleaner ride.
The solution is essentially a self-extinguishing battery that utilizes common blaze-dousing chemicals.
"It replaces the most commonly used electrolyte, which is highly combustible — a medium composed of a lithium salt and an organic solvent — with materials found in a commercial fire extinguisher," the experts wrote.
Importantly, the power pack passed a battery of exams, including successful operation at extreme temperatures. It also survived the crucial nail penetration test, which is exactly as it sounds.
"Driving a stainless steel nail through a charged battery simulates an internal short circuit; if the battery catches fire, it fails the test. When we drove a nail through our charged batteries, they withstood the impact without catching fire," according to Rao and Lu.
A video clip in the Clemson article shows the smoke and flames that are produced when a battery fails the test.
Some lab work was required to make the fire-prevention chemicals compatible in batteries. Low toxicity and zero planet-warming risk were important considerations. The battery can also function for more than a year without losing much capacity, per the experts.
"We were able to produce an electrolyte that had the features we sought," they wrote.
They focused the research on potassium-ion and lithium-ion power packs. More testing needs to be completed to see if the electrolyte will work with the myriad of other battery types, including zinc-, sodium-, and aluminum-ion.
Removing the safety concern could help to expand the growing EV market. For every gas-guzzler replaced by an EV, 10,000 pounds of harmful air pollution can be avoided each year. It can also ease breathing. Recent studies cited by the National Library of Medicine suggest that elevated inhalation of vehicle exhaust can lead to asthma problems among adults — this is particularly noteworthy for people who live near a major highway.
For their part, the Clemson and Chinese experts report that their innovative electrolyte can be easily integrated into existing battery-making processes.
"If the industry embraces it, we expect that companies will be able to manufacture nonflammable batteries using their existing lithium-ion battery facilities," Rao and Lu wrote.
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