Tag: chemical engineering

Science-Watching: Why Do Batteries Sometimes Catch Fire and Explode?

[from Berkeley Lab News, by Theresa Duque]

Key Takeaways
  • Scientists have gained new insight into why thermal runaway, while rare, could cause a resting battery to overheat and catch fire.
  • In order to better understand how a resting battery might undergo thermal runaway after fast charging, scientists are using a technique called “operando X-ray microtomography” to measure changes in the state of charge at the particle level inside a lithium-ion battery after it’s been charged.
  • Their work shows for the first time that it is possible to directly measure current inside a resting battery even when the external current measurement is zero.
  • Much more work is needed before the findings can be used to develop improved safety protocols.

How likely would an electric vehicle battery self-combust and explode? The chances of that happening are actually pretty slim: Some analysts say that gasoline vehicles are nearly 30 times more likely to catch fire than electric vehicles. But recent news of EVs catching fire while parked have left many consumers – and researchers – scratching their heads over how these rare events could possibly happen.

Researchers have long known that high electric currents can lead to “thermal runaway” – a chain reaction that can cause a battery to overheat, catch fire, and explode. But without a reliable method to measure currents inside a resting battery, it has not been clear why some batteries go into thermal runaway, even when an EV is parked.

Now, by using an imaging technique called “operando X-ray microtomography,” scientists at Lawrence Berkeley National Laboratory (Berkeley Lab) and UC Berkeley have shown that the presence of large local currents inside batteries at rest after fast charging could be one of the causes behind thermal runaway. Their findings were reported in the journal ACS Nano.

“We are the first to capture real-time 3D images that measure changes in the state of charge at the particle level inside a lithium-ion battery after it’s been charged,” said Nitash P. Balsara, the senior author on the study. Balsara is a faculty senior scientist in Berkeley Lab’s Materials Sciences Division and a UC Berkeley professor of chemical and biomolecular engineering.

“What’s exciting about this work is that Nitash Balsara’s group isn’t just looking at images – They’re using the images to determine how batteries work and change in a time-dependent way. This study is a culmination of many years of work,” said co-author Dilworth Y. Parkinson, staff scientist and deputy for photon science operations at Berkeley Lab’s Advanced Light Source (ALS).

The team is also the first to measure ionic currents at the particle level inside the battery electrode.

3D microtomography experiments at the Advanced Light Source enabled researchers to pinpoint which particles generated current densities as high as 25 milliamps per centimeter squared inside a resting battery after fast charging. In comparison, the current density required to charge the test battery in 10 minutes was 18 milliamps per centimeter squared. (Credit: Nitash Balsara and Alec S. Ho/Berkeley Lab. Courtesy of ACS Nano)
Measuring a battery’s internal currents

In a lithium-ion battery, the anode component of the electrode is mostly made of graphite. When a healthy battery is charged slowly, lithium ions weave themselves between the layers of graphite sheets in the electrode. In contrast, when the battery is charged rapidly, the lithium ions have a tendency to deposit on the surface of the graphite particles in the form of lithium metal.

“What happens after fast charging when the battery is at rest is a little mysterious,” Balsara said. But the method used for the new study revealed important clues.

Experiments led by first author Alec S. Ho at the ALS show that when graphite is “fully lithiated” or fully charged, it expands a tiny bit, about a 10% change in volume – and that current in the battery at the particle level could be determined by tracking the local lithiation in the electrode. (Ho recently completed his Ph.D. in the Balsara group at UC Berkeley.)

A conventional voltmeter would tell you that when a battery is turned off, and disconnected from both the charging station and the electric motor, the overall current in the battery is zero.

But in the new study, the research team found that after charging the battery in 10 minutes, the local currents in a battery at rest (or currents inside the battery at the particle level) were surprisingly large. Parkinson’s 3D microtomography instrument at the ALS enabled the researchers to pinpoint which particles inside the battery were the “outliers” generating alarming current densities as high as 25 milliamps per centimeter squared. In comparison, the current density required to charge the battery in 10 minutes was 18 milliamps per centimeter squared.

The researchers also learned that the measured internal currents decreased substantially in about 20 minutes. Much more work is needed before their approach can be used to develop improved safety protocols.

Researchers from Argonne National Laboratory also contributed to the work.

The Advanced Light Source is a DOE Office of Science user facility at Berkeley Lab.

The work was supported by the Department of Energy’s Office of Science and Office of Energy Efficiency and Renewable Energy. Additional funding was provided by the National Science Foundation.

Movies and Chemistry: Keeping the Enchantment of Education

Several movies give you an “enchanting” back door or window into chemistry so that you can “beat” the tediousness of regular education and come into the field and its topics via these movies:

I.

The Man in the White Suit is a 1951 British comedy classic with Alec Guinness as a genius research chemist. He fiddles with his flasks and polymer and textile chemistry experiments until he invents a fabric that shows no wear and tear “forever.” This would seem like a great boon to humanity in its clothing needs but the chemist (“Sidney Stratton”) finds that both labor and management reject his discovery violently as it threatens jobs and profits. Textile or fabric polymer chemistry is at the heart of the plot.

Cry Terror! is a taut 1958 crime thriller movie with James Mason and Rod Steiger. The plot involves the terrorist threat of exploding a domestic airliner with a hidden RDX cache (a TNT successor) unless the demanded payment is made.

RDX was used by both sides in World War II. The U.S. produced about 15,000 long tons per month during WWII and Germany about 7,000 long tons per month. RDX had the major advantages of possessing greater explosive force than TNT, used in World War I and requiring no additional raw materials for its manufacture.

Semtex is a general-purpose plastic explosive containing RDX and PETN. It is used in commercial blasting, demolition, and in certain military applications.

A Semtex bomb was used in the Pan Am Flight 103 (known also as the Lockerbie) bombing in 1988. A belt laden with 700 g (1.5 lb) of RDX explosives tucked under the dress of the assassin was used in the assassination of former Indian prime minister Rajiv Gandhi in 1991.

The 1993 Bombay bombings used RDX placed into several vehicles as bombs. RDX was the main component used for the 2006 Mumbai train bombings and the Jaipur bombings in 2008. It also is believed to be the explosive used in the 2010 Moscow Metro bombings.

Traces of RDX were found on pieces of wreckage from 1999 Russian apartment bombings and 2004 Russian aircraft bombings. Further reports on the bombs used in the 1999 apartment bombings indicated that while RDX was not a part of the main charge, each bomb contained plastic explosive used as a booster charge.

Ahmed Ressam, the al-Qaeda Millennium Bomber, used a small quantity of RDX as one of the components in the bomb that he prepared to detonate in Los Angeles International Airport on New Year’s Eve 1999-2000; the bomb could have produced a blast forty times greater than that of a devastating car bomb.

In July 2012, the Kenyan government arrested two Iranian nationals and charged them with illegal possession of 15 kilograms (33 pounds) of RDX. According to the Kenyan Police, the Iranians planned to use the RDX for “attacks on Israeli, U.S., UK and Saudi Arabian targets.”

RDX was used in the assassination of Lebanese Prime Minister Rafic Hariri on February 14, 2005.

In the 2019 Pulwama attack in India, 250 kg of high-grade RDX was used by Jaish-e-Mohammed. The attack resulted in the deaths of 44 Central Reserve Police Force personnel as well as the attacker.

Semtex was developed and manufactured in Czechoslovakia, originally under the name B 1 and then under the “Semtex” designation since 1964, labeled as SEMTEX 1A, since 1967 as SEMTEX H, and since 1987 as SEMTEX 10. Originally developed for Czechoslovak military use and export, Semtex eventually became popular with paramilitary groups and rebels or terrorists because prior to 2000 it was extremely difficult to detect, as in the case of Pan Am Flight 103.

The Russian apartment bombings were a series of explosions that hit four apartment blocks in the Russian cities of Buynaksk, Moscow and Volgodonsk in September 1999, killing more than 300, injuring more than 1,000, and spreading fear across the country. The bombings, together with the Invasion of Dagestan, triggered the Second Chechen War. The handling of the crisis by Vladimir Putin, who was prime minister at the time, boosted his popularity greatly and helped him attain the presidency within a few months.

The blasts hit Buynaksk on 4 September and in Moscow on 9 and 13 September. On 13 September, Russian Duma speaker Gennadiy Seleznyov made an announcement in the Duma about receiving a report that another bombing had just happened in the city of Volgodonsk. A bombing did indeed happen in Volgodonsk, but only three days later, on 16 September. Chechen militants were blamed for the bombings, but denied responsibility, along with Chechen president Aslan Maskhadov.

A suspicious device resembling those used in the bombings was found and defused in an apartment block in the Russian city of Ryazan on 22 September. On 23 September, Vladimir Putin praised the vigilance of the inhabitants of Ryazan and ordered the air bombing of Grozny, which marked the beginning of the Second Chechen War. Three FSB agents who had planted the devices at Ryazan were arrested by the local police, with the devices containing a sugar-like substance resembling RDX.

II.

The movie Khartoum (1966) has General Charles Gordon traveling to Sudan in 1884 to quell the “mad mullah” the Mahdi. (Osama bin Laden of his day).
At the train station where General Gordon starts his trip, there’s a railway ad sign that promotes the use of “Wright’s Coal Tar Soap.”

This gives us a sign of the rise of the modern chemical industry.

III.

Think of “Sherlock Holmes” in terms of all the movies and TV series or the original stories and books:

Holmes has to explain to Watson how he survived the assassination attempt on him by Moriarty, “the Napoleon of Crime” who threw him off the Reichenbach Falls. Holmes explains that he faked Moriarty out and clung to a bush or something and was (obviously) not killed.

Holmes tells Watson what he does when he returns to civilization and travels and studies for some three years:

“I then passed through Persia, looking in at Mecca, and paid a short but interesting visit to the Khalifa at Khartoum, the results of which I communicated to the Foreign Office. Returning to France, I spent some months in a research into the coal-tar derivatives, which I conducted in a laboratory at Montpellier, in the south of France.”

The context implies the year 1894.

There is clear evidence that Mr. Holmes was deeply involved in the research of coal-tar derivatives as early as 1889 when the events of the Copper Beeches matter were transpiring.

We are told that on an evening in 1889, Mr. Holmes was seated in 221B Baker Street at the deal table loaded with retorts and test tubes. He was settling down to one of those all-night chemical researches in which he frequently indulged.

The research work was interrupted by a message of distress from Violet Hunter. Watson found that there was a train the next morning, and Holmes tells Watson:

“That will do very nicely. Then perhaps I had better postpone my analysis of the acetones as we may need to be at our best in the morning.”

It is clear that Holmes was engaged in coal-tar research long before his visit to Montpellier in the south of France.

The quotation from the Copper Beeches story refers to acetones, not to coal-tar derivatives.

“In the fractional distillation of coal-tar, the distillate separates into five distinct groups or layers, depending upon the stage of the process and the amount of heat applied. Category-one of the five includes benzene, toluene, xylenes and cumenes.

Acetones [dimethelketone-CH3COCH3] may be derived from the oxidation of cumene. And cumene [isopropylbenzene-C6H5C(CH3)2] is derived by distillation from the coal-tar naphtha fractions.”

Cumenes are derived from coal-tar, and acetones are derived from cumenes. Thus, a study of the acetones is, necessarily, research into coal-tar derivatives.

The rise of chemical engineering and organic chemistry are at the heart of the Sherlock Holmes stories.

Thus we can “climb” into chemistry via these books and movies and keep a feeling of enchantment as a kind of educational “shoehorn.”