What is a wake for the smart lithium-ion battery to cause an explosion accident and its workaround?

ByTechStage

The lithium-ion battery of the smartphone explodes and ignitesIs causing damageAlthough it is talked about, in fact it is not widely known that batteries can make a big accident if you make a mistake. It is summarized how the battery stores and releases electricity and what kind of danger lurks there.

The science behind exploding phone batteries - The Verge
http://www.theverge.com/2016/9/8/12841342/why-do-phone-batteries-explode-samsung-galaxy-note-7

As The Verge, which explains about lithium-ion battery technology, says, "It is natural for chemicals used in batteries to explode," the materials used in lithium-ion batteries are always at risk of explosion It can be said that the state is next to one another. In particular, in the current lithium ion battery, which is said to reach 90% of the theoretical upper limit value, a problem arises once the very high energy is contained in the battery cell And the energy that was contained will be released at once.

Briefly describing the structure of the lithium-ion battery, its inside consists of two (1) anodeelectrode, A "separator -" that insulates the electrodes from touching, and "ElectrolytesIt is composed of. The lithium ion battery uses lithium oxide as the material of the "positive electrode", and it has a name because it is a mechanism to create lithium ions as a source of power.

When the lithium-ion battery is charged, energy is stored inside by lithium ion moving from the cathode to the anode. When extracting power from the battery, current is generated by moving lithium ions from the anode to the cathode. At this time, a separator is inserted to prevent the situation where substances to move ions (electrons) inside are electrolytes, the two electrodes directly touch and release high energy. Being in the worldGalaxy Note 7 batteryThen, it is thought that this separator was defective, the two electrodes directly touched, and the current was generated at once, leading to an explosion.

For details of lithium-ion battery, it seems to be understood well by referring to the following page.

Knowledge of lithium-ion batteries - Knowledge of lithium-ion batteries
http://michinokutrade.hateblo.jp/entry/2015/12/06/112614

"Temperature control" and "prevention of overcharging" are important for stable operation of lithium-ion batteries. Many technologies are being applied to this control in lithium-ion batteries, because they are all directly related to safety.

Electrolytes that electrons move have heat-sensitive characteristics, chemical reactions occur when strong electric current flows or electrons move in a state exposed to a high-temperature environment such as inside a car during the day, gas and heat Will occur. This heat generates a "positive feedback" that a further chemical reaction occurs so that the lithium ion battery will be in a state of "thermal runaway", leading to explosion and ignition as the worst case. Devices using lithium-ion batteries such as smartphones and cameras sometimes have the function of automatically shutting down the power when the temperature of the main unit becomes too high, but this is because of the thermal runaway of the lithium ion battery It is a protection function built in to prevent.

ByJuanerre

One overcharge occurs by sending energy that exceeds the capacity that can be stored in the battery. This happens when the bucket is filled with excessive water, and it occurs when the lithium ion battery is too much lithium ions to move to the anode. Even if charging speed is slowed down, overcharging can not be prevented, there is no way to prevent only cutting current for charging.

Therefore, the lithium-ion battery has built-in function to monitor the charged capacity, so that you can always grasp the correct battery level. Even if the smartphone is connected to the charger overnight, there is a safety device built in which the charging automatically stops when the lithium ion battery of the smartphone is fully charged.


According to Mr. Dan Steingard, a material engineering scholar at Princeton University, it can be said that charging and discharging of the battery can be compared to the situation where the rubber band is stretching and shrinking. Charging is the same as stretching the rubber band by hand for energy and it is said that the discharge is the same as shrinking the rubber band by releasing the hand, and if you stretch the rubber band too much, it will be cut someday and the battery Explains that it is similar to breaking over with overcharging.

Also, in addition to overcharging, "fast charge" to speed up the charging speed can also cause damage to the lithium ion battery. A properly designed lithium-ion battery works according to the situation, but if overcharging or overcharging is done, symptoms such as "plating" will occur on the surface of the material of the battery Occur.

It is said that it can be compared to a state of laying eggs on "egg pack" carrying raw eggs. There is nothing wrong with packing 10 eggs slowly into 10 egg cartons, but if you speed up putting eggs and trying to put more than 11 eggs, the eggs that could not fit well go I have lost the state of being left behind in the egg pack. Eggs left behind once are then left in the pack, even if the eggs were taken out (= discharged). In that state put the egg again (= charging), a new egg is placed on the remaining egg and it will be stacked one after another.

Lithium particles correspond to eggs in an actual battery, protruding "dendrite (dendrite)" is formed on the surface of the material by repeating unnatural charge and discharge, and the circuit is short-circuited inside the battery This will cause the battery to explode or cause a fire.

ByRakka

Furthermore, raising the voltage to pack more energy also leads to damage to the battery. Voltage expresses "strength of force"Potential differenceAlso called. Just as the fall of the waterfall becomes bigger the force becomes stronger, the higher the voltage, the stronger the current power. There is no problem when energy is successfully stored, but once problems arise, energy will be released with a stronger force, leading to a major accident.

In order to prevent these accidents, improvement of materials has been continued, and materials such as "ionic liquid" are being developed as electrolytes that gas is less likely to generate even when high heat is applied. In the first place, lithium-ion battery is a device full of human wisdom that cover difficulty of control with sharpened technology. Mr. SteinGard said, "It is potentially a bomb-like thing, stuffed with such energy and can be released in a short time, no matter what kind of substance it is made of," , Tell the merits and merits of high performance batteries.

Battery technology still continues to evolve, but its speed can not necessarily meet the harsh demands of people. In order to increase the safety of the battery, not only the manufacturer and the manufacturer are required to properly design and manufacture, but also users do not use it in too hot state, do not use illegal remodeled batteries, etc. It seems important to keep in mind the risk avoidance measures.

ByNicolas Nova