Causes and type analysis of common explosion of lithium batteries

　　Author ：Iflowpower – Portable Power Station Supplier

1, the raw material, the presence of severe quality problems, tightly the quality of the electrolyte; 2, the pole piece absorbent, water and electrolytic solution, there is a large amount of gas and heat; 3, the amount of liquid is less, charge and discharge Larger, affecting lithium ion transmission; 4, the cover welding, the sealing process is poor, the sealing performance is poor, there is a leakage, the external moisture is entered; 5, the internal micro short circuit, it is a dust burr, more derived from the pole cutting And cut knife burrs; 6, the current is too large, the negative electrode does not accept more lithium ions, forming the dendrites, the diaphragm short circuit; 7, the battery is overcharge, the material structure collapse, the lithium binder forming piercing diaphragm. The explosive type decomposes the type of explosion of the lithium-ion battery, tightly divided into short circuit and overtake, short circuit is also divided into internal short circuit and external short circuit. Let's talk about the external short circuit, the principle is simple, a conductive material, from the outside of the battery, Unicom and negative.

When the external short circuit occurs, the current becomes large, the inside of the battery begins to heat, when the heat is large, the electrolyte will analyze, a large amount of gas, battery bulge. We said that many diaphragms have a closed cell function, reaching a certain temperature separator, blocking lithium ions, thereby blocking chemical reactions, current falling, slowly falling, thus arresting battery explosion. Of course, the above is only based on a quality diaphragm.

The internal short circuit is to be because the brass foil is pulling the membrane of the aluminum foil, or the branches of the lithium atom wear the diaphragm. These fine needles can cause micro-short circuits. Because there is a certain resistance value, the current is not very big.

Copper aluminum foil burrs will result in the process of processing, and the phenomenon of observational is battery leakage, self-discharge, mostly can be tested by short-circuit detector. Moreover, since the glitch is small, sometimes it will be burnt, so that the battery will return to normal. Therefore, the probability of the explosion caused by burrs is not high.

Burbs are from slit, and there is a burr. The dense crystal source will cause a large current, lithium lithium, etc. Explosion caused by pre-charge is more common.

Battery over, the plate is everywhere, the needle lithium metal crystals, the puncture point is everywhere, there is a micro-short circuit everywhere. Therefore, the battery temperature will gradually increase, and finally high temperature will electrolyte gas. This situation, whether it is too high to make the material burning explosion, or the outer shell is first broken, so that the air invested in and lithium metal, it is an explosion! ! ! However, this explosion caused by excessive internal short circuit is not necessarily occurring at the time of charging.

We have a common mobile phone battery decomposition, and there is such a situation that the battery temperature has not been high enough to burn the material, and the gas that appears is not enough to break the battery housing, we will stop charging, with the mobile phone to go out. At this time, the heat of many micro-short circuits, slowly increase the temperature of the battery, after a period of time, only explosion. The common description of the consumer is to pick up the phone and find that the phone is hot, and then exploded.

Although there are many automatic power-off functions in this chance, but still tips, try not to charge for a long time. Whether it is charging or discharging, we have a standard, usually used to stop at a voltage. Taking the ternary battery of the graphite negative electrode of nickel-manganese acid as an example, when the battery charging voltage is higher than 4.

2V, the danger will quietly, the higher the voltage, the higher the danger. Because when the voltage is higher than 4.2V, the number of lithium atoms in the positive electrode material is reduced, and the structure of the storage atom will collapse, and it is not reversible.

If the negative pole has been filled with lithium ions, lithium ions will generate lithium metals in the surface of the negative electrode, which is the dendritic crystal, these dendrites will pierce the diaphragm, so that the positive and negative short circuit. The overcharge will increase the temperature, the temperature exceeds 180 ¡ã C, the electrolytic solution will analyze, there is a large amount of gas and heat, the housing expands, after breaking, oxygen into the lithium metal, drastically, will also explode. Therefore, the upper limit of the charging voltage is a protection measures.

There is also a voltage lower limit when the lithium ion battery is discharged. Some materials will be destroyed when the battery voltage is below 2.4V.

Also because the battery will be self-discharge, the more long voltage is lower, so it is best not to put it until 2.4V when discharged. The lithium ion battery is discharged from 3.

0V to 2.4V, and the released energy only accounts for about 3% of the battery capacity. Typically, our ternary batteries use 3.

0V as an ideal discharge cutoff voltage. So don't be overwhelming is another protection measures. In addition to the charging cutoff voltage, the discharge cutout voltage, we also use current to protect the battery, which is the magnification performance of our usual concern, and those such as a few minutes of osther select special materials, such as graphene.

It can be easily understood as your tea cup, with mesh tea, if you slowly pour the water, you will not blocked at all, the water will not splash. But you changed a big faucet, you will find it online, I can't go in. The damage of the large current to the battery is characterized by excessive current, and the lithium ion does not enter the storage, which will focus on the surface of the material.

After these lithium ions receive electron, there will be a lithium atomic crystallization on the surface of the material, which is the same as the excessive charge, which will cause dangerous. In the case of broken, it will explode.