Some knowledge of over-heating and explosion of lithium batteries

Lithium batteries are now commonplace in electronic devices, including smart-phones, laptops, electric cars, and even airplanes. But the recent battery overheating and explosion of Samsung's Galaxy Note 7 flagship phone has prompted consumers to re-examine the safety of lithium batteries.

Last week, the Federal Aviation Administration issued a consumer warning not to turn on the Note7 phone or charge it, or even put it in checked luggage, according to us media reports. Many international airlines have similar restrictions. In addition, the Consumer Product Safety Commission has issued recommendations to stop charging Note7 phones.

The serious incident at Note7 makes it necessary to relearn some of the knowledge about lithium batteries, especially why they overheat or explode.

It's time to tell you what a lithium battery is and why the Samsung Note7 exploded.

What is the reason why lithium batteries are so popular?

The technology of lithium batteries is completely different from that of the No. 5 and No. 7 batteries(such as those in the TV remote control). Lithium batteries can be recharged repeatedly and integrated directly into electronic equipment. Lithium batteries need to rely on lithium materials. To provide electricity.

Because lithium batteries can store electricity efficiently and can discharge slowly, lithium batteries have become very popular batteries and are used in laptops, smart-phones and other fields.

Compared to other ancient battery technologies, lithium batteries can store two to four times as much electricity in the same volume, said Stephen Hackney, a professor of materials science at Michigan Tech University.

How does the lithium battery work?

Like all batteries, lithium batteries first need to store electrical energy and then gradually release it through controlled chemical reactions. A lithium battery has two electrodes, where electricity can enter or leave the battery. These two electrodes are called anodes and catheters, respectively.

In layman's terms, consumers can think of these two electrodes as plus or minus numbers on ordinary batteries. When discharging using a lithium battery, lithium ions move from the cathode to the anode, and when charging, lithium ions move from the anode to the cathode.

Relevant components exist inside the lithium battery to separate the anode material from the cathode material. If the two materials come into contact, they will trigger combustion or explosion.

How did the explosion come about?

The professor said that the reason why so much electricity can be stored in lithium batteries is because lithium is an active material that "reacts with almost any material." This property can cause an explosion.

The professor said that the most common cause of explosion in lithium batteries was a mistake in charging. In electronic devices that use lithium batteries, there are often related software that sets the charge of the lithium battery and the charging speed. If the relevant setting is wrong, it will cause the compound in the battery to become unstable, and there is a problem that researchers call "thermal runaway", which will trigger combustion or explosion.

Lithium batteries can also cause explosions when they are too hot. Therefore, some smart-phones will actively alarm when the battery temperature is too high, prompting users to cool down.

Another cause of overheating and explosion is in the manufacturing process, or the carelessness of the user. If you leave an unwanted material(such as a small iron sheet) in the battery manufacturing process, this will cause the battery to short-circuit and cause heat to lose control.

In addition, after the user's electronic equipment falls, it will also cause problems with the separation materials of the anode and cathode in the lithium battery, leading to overheating or explosion.

What happened to the Note7 battery?

So far, it looks like a manufacturing problem. Samsung electronics had previously announced that it had caused at least 35 cases of lithium batteries on Note7 phones to overheat due to "very rare manufacturing errors". Samsung's alleged process mistakes are known to cause contact between the anode and the cathode.

Note7 has just been on the market for two weeks, but Samsung Electronics has decided to recall its products and replace new phones with customers it has purchased.

Does lithium battery overheat often appear?

Professor Stephen Hackney of the Michigan Institute of Technology gave good news, saying that overheating of lithium batteries is not uncommon. Especially in high-end electronic equipment, as long as manufacturers pay attention to quality control, there will be no such problems as process errors.

However, there have been many recalls of lithium battery products in history. In 2006, for example, Dell recalled 4 million laptops with battery overheating problems. In 2013, the Boeing 787 manufactured by Boeing of the United States was forced to suspend flights because of reports that lithium batteries on the aircraft were prone to overheating.

Also this summer, American manufacturers recalled more than half a million suspended skateboards(the hottest gift last Christmas), mainly due to overheating and explosions of lithium batteries.

Will regulators investigate overheated batteries?

At present, the safety and quality of lithium battery products have been required by government regulatory agencies and international organizations in many ways. This is also a reason why lithium batteries are overheated or explode.

For example, the U.S. Department of Transportation has strict regulations on how to transport lithium batteries safely.

Many regulators also require that lithium batteries present in consumer electronics must undergo rigorous safety tests. The U.S. Consumer Product Safety Commission has organized several battery recalls in the past and is currently collaborating with Samsung Electronics to conduct the Note7 recall in the United States.

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