When should the phone be charged?

In the past, samsung Note 7 phones have experienced spontaneous combustion and explosion accidents. For a moment, safety issues about lithium batteries and mobile power supply have become the focus of public attention.

“The mobile phone that can explode who dares to use!”

“Mobile phone is not a bomb, how easy to explode? There must be a conspiracy!”

What exactly is a lithium battery? Why do airline counters always remind us that lithium batteries can’t be in checked luggage? And the recent cellphone explosion, why did it happen?


A simple understanding of lithium battery

Lithium batteries are complex and complex. In short, lithium (Li) and its alloys and compounds can be used as the negative electrode chemical battery, which can be called lithium battery. Lithium batteries commonly used in mobile phones and electronic products are, more formally, “lithium ion secondary batteries”, which can be charged and discharged and reused.

“Why do you have to use lithium batteries? There are safer batteries, why not?”

That’s a good question! Before I answer this question, I would like to ask you about the thickness, weight and standby time of your mobile phone. What is your expectation?

“Of course the lighter, the longer standby time the better!”

That’s why lithium batteries stand out: they’re low in density (0.53 grams per cubic centimeter, lighter than water) and high in voltage (Li+ + e- Li reactive electromotive force is 3.0 volts), so “energy density” is high. Isn’t it beautiful?

In addition, lithium batteries have the advantages of not having to worry about memory effect, long life and wide range of applicable temperature. They are almost the only choice for electronic products! But lithium-ion batteries have also been the subject of several explosions.

Why do lithium-ion batteries explode?

The cause of the battery’s spontaneous combustion and explosion is usually overheating.

Everyone must have this experience: when the phone is charged, or used for a long time with high power, like watching TV or video, the phone will be hot. That’s because a lithium-ion battery, whether charged or discharged, moves the ions between the positive and negative poles, a process that generates heat. If the battery or circuit is not designed well and the thermal energy is produced rapidly, the thermal runaway phenomenon may occur: the release of heat causes the reaction rate to increase, and the increase of the reaction rate causes more heat release, making the temperature higher and higher, the reaction rate faster and faster, and finally causing a fire or explosion!

The cause of heat loss is nothing more than manufacturing defects, or abnormal use, such as short circuit, forced charging or too rapid charging, discharge. The Note 7’s recent explosion was just one of the reasons.

According to the observation of news, the cases of explosion at the beginning were all happened during charging. Some people speculated that the reason was that the manufacturer enhanced the function of quick charging, which led to the overheating of the battery charging process. However, it was later found that some of the explosions occurred during the delivery. It can be seen that the battery explosion problem is not only the instability of the protective layer of the battery, but also the formulation of electrolyte or the insulation of positive and negative electrodes.

How to avoid it?

Even without the Note 7, our lives are full of lithium batteries. There are several points to note about lithium batteries:

Lithium battery is vulnerable to damage when used to extremely low power, resulting in shorter battery life and less battery capacity.

Overcharging, that is, continuous charging at full charge, can easily damage the battery.

The first point to avoid is as simple as charging as soon as the battery displays 15 or 20 percent or less.

As for the second point, mobile phones are now overcharged with protection, and the charging will stop when the battery is full, which is not likely to cause problems. In addition, the lithium battery can’t stand the heat to the cold and afraid of fall below 0 ° C over 40 ° C or charge and discharge in the environment, not only the efficiency is poor, also can make the battery is damaged. If the phone is dropped, it may damage the battery’s internal security protective layer and cause accidents.

When flying, checked luggage is often subject to collision, and the temperature in the cargo hold is often changed due to different weather conditions, which increases the risk of lithium batteries in such an unstable environment. This is why lithium batteries now have to be transported with passengers’ carry-on luggage and cannot be placed in checked luggage.

Therefore, it is suggested that if you have an old mobile phone in your home, please send it to the recycling center and don’t throw it away as usual. Because of the lithium battery, you don’t know which day it will be dropped or poked, so as to avoid unnecessary risk factors.

Since the advent of lithium ion batteries, there have been several innovations in consumer electronics. However, the desire of human beings is endless, and people’s requirements for batteries are higher and higher. We not only want batteries to be thinner and shorter, but also to have a longer endurance, and hope that the charging time is as short as possible. In such a situation, in addition to relying on the progress of science and technology, consumers must also develop good use habits, so as to make good use of the convenience of science and technology and avoid accidental injury.

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