.Our Potentially Explosive Future

The chemistry behind lithium batteries could cause spontaneous fires

On July 14 Los Gatos resident Christopher Chambers got a call saying that his wife and daughter had not arrived for their doctor’s appointment. Filled with dread, he and his young son immediately drove towards the doctor’s office when they saw smoke in the sky ahead.

A white Tesla Model Y had veered into the opposite lane, crashed into a tree and burst into flame. Chambers tried to approach the wreck, but was prevented by police. They checked the car’s VIN number and confirmed his worst fears. Chambers’s 44-year-old wife Beidi and 12-year-old daughter Elyse died at the scene.

“I was left with unbearable questions–were my girls conscious in the end? Did they suffer?” Chambers later wrote on Gofundme where his appeal for financial aid quickly almost doubled its $50,000 target.

According to Chambers, witnesses claimed that within 30 seconds the flames around the vehicle were too hot to approach, and one apparently said it was “like an inferno” and all he could see inside was smoke.

“We investigate every single incident where the driver alleges to us that their vehicle accelerated contrary to their input, and in every case where we had the vehicle’s data, we confirmed that the car operated as designed,” wrote Tesla in a press statement from January 2020. “In other words, the car accelerates if, and only if, the driver told it to do so, and it slows or stops when the driver applies the brake.”

secure document shredding

Chambers does not believe what he has been told by police or the vehicle data that indicates user input of excessive speed. He said his wife would not have driven at 95 miles an hour with their daughter in the car. “She just didn’t drive like that,” said Chambers.

Chambers plans to bring suit against Tesla for the alleged unintended acceleration and fire.

With this lawsuit he joins many others globally and nationally who have alleged cases of unintended acceleration. Tesla has refuted these claims. In 2021, the National Highway Traffic Safety Administration (NHTSA) investigated the issue and determined that all the reported cases it evaluated were due to user error, although they recently reopened the investigation after another petition.

New EDR Data Findings

“In many cases of sudden acceleration over the past few years the driver has claimed that his/her foot was on the brake pedal or on the floor during the incident instead of on the accelerator pedal. However, a subsequent look at the EDR data showed that the accelerator pedal was pressed to a maximum of 100% in less than a few seconds during the incident, apparently showing that pedal error was the true cause of the incident,” wrote AutoSafety.org in a June report.

The safety document goes on to explain how the accelerator sensors can potentially malfunction, leading to no action needed by the driver to inadvertently accelerate their vehicle. “A vehicle defect can cause the digitized outputs of the accelerator pedal sensors to increase up to 100% without the driver stepping on the accelerator pedal even though the analog outputs of the accelerator pedal sensors remain at their un-pressed values of 0%,” wrote the document. “The vehicle defect in this case is that the control software allows ADC calibration with an incorrect value of the calibration voltage.”

When it comes to fires, cases are easier to verify. In February this year a brother and sister in Sacramento were driving eastbound on Highway 50 when their Tesla began emitting smoke. They pulled over and exited the vehicle just before the engine caught fire. There are several similar stories circulating the internet.

Tesla and other EV car manufacturers assert that electric vehicles are far less prone to catching fire than internal combustion engine vehicles, and fully electric vehicle sales are climbing with a market share of 7.2% in the first quarter of 2023. This is a jump from 4.3% last year in the same period.

A recent study by AutoinsuranceEZ compared results per 100k sales and reported 25 EV fires compared to 1,530 for gas cars, with just over double 3,475 for hybrids.

When they do happen, fires involving electric vehicles are known to be severe. Firefighters often have to use thousands of gallons of water to extinguish them due to the intense heat. In order to conserve water, some firefighters have used less conventional methods, such as placing the burning wrecks in containers of water or sand. This also guards against the possibility of fires reigniting even after they’ve been extinguished.

“It can take between approximately 3,000-8,000 gallons (11,356- 30,283 liters) of water, applied directly to the battery, to fully extinguish and cool down a battery fire,” wrote Tesla’s 2016 Model S emergency response guide. “Battery fires can take up to 24 hours to fully cool.”

DRIVING SAFELY As more and more vehicles turn electric, lithium battery usage will continue to grow. Photo: Shutterstock Armands photography

The Lithium Reaction

Electric Vehicles as well as most electronic devices use lithium, a soft alkali metal that is very reactive. Fires involving batteries are exacerbated by a process called ‘thermal runaway,’ chemical chain reactions that can lead to a rapid and exponential increase in temperature.

To understand this chemical reaction, it helps to know how a battery works. There are two basic components to a battery; the electrolyte (typically a liquid) and a cathode (typically a solid), which is what the ions from the electrolyte can transfer into. Lithium is only number three on the periodic table, so its ions are very light, small and mobile. Ions are electrically charged particles that are formed when atoms gain or lose electrons. When a battery discharges, ions are moving from the electrolyte into the cathode and when a battery charges up, the opposite process occurs.

“When lithium ion batteries burn, the cathode material breaks down and releases O2, and the battery combustion will also release CO and other combustible gasses,” wrote a 2017 ScienceDirect report about the effects of fire and explosion suppression within lithium ion batteries. “The large amount of heat released by internal reaction can also provide energy for lithium ion battery combustion.”

When a battery undergoes repeat use, the many chemical reactions can cause residual compounds to form on the interface where liquid and solid materials meet. This causes a battery to be less efficient over time; the reason why an old laptop or phone won’t hold charge for as long as a new one. That’s unavoidable, but an additional problem can occur when little finger-like deposits called dendrites form and spread into the electrolyte. These dendrite formations can be conductive and can even short-circuit the battery.

The exact chemistry behind this is not perfectly understood by scientists, but when this reaction happens, a lot of energy can be discharged in a very short amount of time, leading to a sharp increase in temperature and even combustion. This is why the TSA, for example, warns against bringing lithium-ion batteries into airplane cabins.

“Spare (uninstalled) lithium ion and lithium metal batteries, including power banks and cell phone battery charging cases, must be carried in carry-on baggage only,” writes TSA.gov. “Lithium metal (non-rechargeable) batteries are limited to two grams of lithium per battery. Lithium ion (rechargeable) batteries are limited to a rating of 100 watt hours (Wh) per battery.”

Many people already know to watch out for potentially faulty batteries. If they are taking an unusually long time to charge, show swelling or have any corrosion, it’s best to take them to a recycling center. Batteries should not go in the trash.

Fire Departments Respond

A concern is that fire departments around the country may not be adequately prepared and trained to handle these situations. “Lithium-Ion Batteries: Are You Ready?” was the theme of this year’s Firefighter Safety Stand Down.

An initiative of all the leading U.S. fire prevention agencies, Safety Stand Down is a week in June when departments are asked to suspend non-emergency activities so that all shifts can participate in the training.

“Lithium-ion batteries power a vast range of products and equipment, from laptops and smartphones to micro-mobility devices, electric vehicles and energy storage systems,” wrote Safety Stand Down’s 2023 press release. “[The week] will be broken down into five daily focus areas: recognition of hazards, firefighting operations, firefighter safety, post-incident considerations and public education.”

As most major car manufacturers have set goals to release more EV options or completely transform their fleet from combustion to electric, other industries will need to develop new safety standards as well.

Community Concerns

Richard Stover, a retired astronomer who lives in Santa Cruz, became concerned about the issue when he learned that a new parking garage was going to be built in the city and include only one entrance and exit. As the owner of a Honda hybrid EV, he’d been casually aware of battery fire incidents in the news. In particular, he was alarmed by the fact that toxic hydrogen fluoride gas is released during such fires.

“Are residents going to be protected from that [gas] and is there any way for the fire department to get in there and get people out?” he asked. “I think the likelihood of a fire is relatively low, but the consequences of that happening with housing above could be very serious.”

After sending a report on the matter to council members as well as the fire chief, he’s gotten no response. “I don’t know if they’re taking any of the issues seriously,” said Stover. “I hope it’s not the case, as it so often seems to be, that nothing happens until something really bad happens.”

Additionally, until just recently there were no national standards for the installation, operation or maintenance of EV charging stations. Last year, the Federal Highway Administration and U.S. Department of Transportation released regulations setting minimum standards and requirements for projects funded under the National Electric Vehicle Infrastructure (NEVI) Formula Program. NEVI is a program that will provide $5 billion in funding to states to build charging infrastructure as part of the Biden Administration’s Bipartisan Infrastructure Law.

When it comes to regulating EV charging site design, the rule “encourages states and other designated recipients to require any necessary fire prevention strategies,” but leaves the regulation of these codes to the building industry, according to the announcement.

“To address climate change, we all must eventually convert to electric vehicles,” said Stover. “Unless there is some dramatic breakthrough in battery technology, we will all be using lithium batteries in most of those vehicles.”

Lithium Batteries and the Future of Safety

Many scientists are working hard to make safer lithium batteries, especially in regards to electric vehicles. Michael Zuerch, assistant professor in the  University of California at Berkeley’s Department of Chemistry, became interested in this field when he considered how all studies that had been done on the internal interfaces of lithium-ion batteries, essentially had been done post-mortem.

A researcher would take a perfectly good battery, cycle it thousands of times in a lab until dendrites developed, and then cut it open to look at them under a microscope.

“What caught my attention was that it would probably be more useful to be able to look at these structures as they form in real time so that you can watch things happening without taking [the battery] apart,” said Zuerch.

    This was an ambitious idea. Zuerch and his team had to travel across the globe to use an electron-free laser called SPring-8 Angstrom Compact free electron LAser (SACLA) in Harima Science Garden City, Japan. The x-ray radiation spectroscopy allowed Zuerch’s team to view the chemistry at work inside the battery.

Zuerch and his team decided to skip lithium-ion batteries altogether, finding it more useful to look at a material that is being tested for use in solid state batteries, lithium lanthanum titanium oxide (LLTO). Their aim was to learn more about how the movement of small charge-bearing ions would interact with the movement of the heavier LLTO atoms.

“It’s like if you have a lot of heavy people dancing in a room, and then you have a skinny person who wants to run through,” said Zuerch. “The more that people move, the more difficult it gets.”

The team discovered that some of the movement from the heavy atoms impedes the flow of lithium-ions, and some of their movement can help by pushing the ions and increasing their activity. It will take many more similar studies until a consensus on this is reached, but being able to observe this movement in real time is a breakthrough that could help engineers refine the design criteria for this new technology.

“Our research provides a better understanding of the surface and interface characteristics of solid-state electrolyte materials and the molecular-level interactions at play at an interface that limit the ion mobility,” Zuerch said in an April press release issued by the school’s chemistry department. “Understanding such phenomena enables us to focus on designing better interfaces in the future and also provides impetus for guided design of future solid-state electrolytes.”

Solid-state batteries have been highly anticipated for years and for good reason. They’re more durable and could carry more charge, thus extending the range of electric vehicles. In a crystal form, like LLTO, they could be small enough to be grown directly on a microchip, handy for small devices like smart watches. Many people are expecting potentially safer results from these batteries.

As their name implies, solid-state batteries use a solid electrolyte substance between the anode and cathode, yet it should still be porous or spongy enough to let the ions pass through and do their energy-bearing work. Because there’s no longer the problem of a liquid interfacing with a solid, these batteries are far less reactive and far less flammable. You can find people on Youtube cutting or smashing solid-state battery packs, and watch nothing happen at all.

“I don’t even know how you would short-circuit such a battery,” Zuerch commented on their durability.

Why then, when lithium-ion batteries have so many known flaws and solid-state batteries are seemingly so superior, are people not using more of the latter? In Zuerch’s case, his LTTO crystal was a perfect lab-grown specimen, however, producing them at scale is a challenge. “Detailed understanding of the involved lithium dynamics [within solid-state electrolytes] is missing due to a lack of inoperando (spectroscopic) measurements with chemical and interfacial specificity,” wrote an April article on the topic by Nature Materials journal.

Many, like Santa Clara County-based startup Natron Energy are placing their bets on sodium-ion batteries. The company is using the salt-based pigment commonly known as Prussian blue as the basis for its batteries. They claim to be one of only five companies in the last century to achieve commercial scale success with a new battery chemistry.

“Just think about when lithium-ion batteries were invented and how long it took until they made their way into all our computers and phones,” said Zuerch. “With solid-state electrolytes, we are only a few years into even knowing that this is a usable approach. It’s going to take time.”


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