Who’s Afraid of the Big Bad Battery?

Author:
Jason Lomberg, North American Editor, PSD

Date
07/02/2020

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Just how dangerous are electric car batteries? Objectively, not very, but EVs and hybrids are the new kids on the block, and new is scary. And a new battery electrolyte developed at Stanford could help alleviate our collective anxiety.

We’ve all seen the headlines – EVs catching fire after accidents, batteries catching fire while they’re charging, and lots more, some exaggerated, some not. To read the media coverage, you’d be forgiven for thinking EVs were a deathtrap.

If we set aside the fear of the unknown, EVs are no scarier than gas-powered vehicles – from 2003-2007, the National Fire Protection Association reported 287,000 vehicle fires per year, causing an average of 480 civilian deaths, 1,525 civilian injuries, and $1.3 billion in direct property damage annually. This amounts to 31 highway vehicle fires per hour.

And this was all vehicles -- mechanical failure or malfunction, such as leaks or breaks, backfires, or worn-out parts caused 49% of the fires, while electrical failures or malfunctions accounted for 23% (and that’s not necessarily electric batteries).

But fear isn’t logical. And EVs are new and scary.

EVs have been involved in the normal rate of high-speed accidents, but there’s often a wrinkle or two. In 2011, a Chevy Volt caught fire three weeks after crash testing, and while further testing revealed acute safety risks, the National Highway Traffic Safety Administration (NHTSA) concluded that “all vehicles –both electric and gasoline-powered – have some risk of fire in the event of a serious crash.”

When Tesla became embroiled in a series of high-profile accidents, Elon Musk pointed to NFPA stats which said that a fire was five times more likely in a gas car than a Tesla (and one would assume, similar stats for most EVs and hybrids). But new developments complicate those figures.

In newer EVs, lithium metal batteries are favored over standard lithium-ion batteries in EVs, because the former has a higher energy density. But this comes with a trade-off.

According to Zhenan Bao, the K.K. Lee Professor in the School of Engineering at Stanford, "during operation, the lithium metal anode reacts with the liquid electrolyte. This causes the growth of lithium microstructures called dendrites on the surface of the anode, which can cause the battery to catch fire and fail."

Professor Bao and his team added fluorine atoms onto the electrolyte molecule, based on the presumption that this would make the liquid more stable. And the early results were promising – the battery retained 90% of its initial charge after 420 cycles of charging and discharging (vs. 30 cycles for normal lithium metal batteries), and the new electrolyte was also far less flammable.

This could go a long way towards making a new – and by any objective measure, more efficient – technology a bit less frightening.

PSD

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