What is the cause of the explosion of lithium batteries?

When the capacity of the negative electrode is insufficient, or there is no capacity at all, part or all of the lithium generated during charging cannot be inserted into the interlayer structure of the negative electrode graphite and it is deposited on the surface of the negative electrode to form a protrusion. And this protrusion is more likely to cause lithium to precipitate during the next charge. After several tens to hundreds of cycles of charge and discharge, the "dendrites" will grow up and eventually pierce the diaphragm paper. A short circuit is generated inside. The battery is discharged abruptly, generating a large amount of heat, burning the diaphragm, causing a larger short circuit phenomenon. The high temperature will decompose the electrolyte into a gas, and the negative carbon and the diaphragm paper will burn, causing the internal pressure to be too large and the outer casing of the battery cannot be subjected to this pressure, the battery will explode.

Excessive moisture content

The water can react with the electrolyte in the battery to produce a gas. When charging, it can react with the generated lithium to form lithium oxide, which causes the capacity of the battery to be lost. It is easy to overcharge the battery to generate gas and decompose the water. The voltage is low, and it is easy to decompose and generate gas when charging. When the gas generated in this series will increase the internal pressure of the cell, the cell will explode when the cell's outer casing cannot withstand it.

Internal short circuit

Due to the internal short circuit phenomenon, the battery discharges a large current, generates a large amount of heat, burns the diaphragm, and causes a larger short circuit phenomenon, so that the battery core generates high temperature, which decomposes the electrolyte into a gas, causing excessive internal pressure. When the cell's outer casing cannot withstand this pressure, the cell will explode.

Upper glue

During laser welding, heat is conducted through the casing to the positive ear, so that the temperature of the positive electrode is high. If the upper adhesive tape does not separate the positive electrode and the diaphragm, the hot positive electrode will cause the diaphragm paper to burn out or shrink, resulting in an internal short circuit and formed an explosion.

High temperature adhesive tape wraps the negative ear

When the customer is spot welding the negative electrode, the heat is transferred to the negative ear. If the high temperature adhesive tape is not attached, the heat on the negative ear will burn the diaphragm, causing an internal short circuit and forming an explosion.

The bottom glue is not completely wrapped around the bottom

When the customer spot welds the bottom aluminum-nickel composite strip, a large amount of heat is generated in the bottom shell wall, and the bottom of the core is conducted. If the high temperature adhesive tape does not completely enclose the diaphragm, the diaphragm will be burned, causing an internal short circuit and an explosion.

Overcharge

When the battery cell is overcharged, the lithium of the positive electrode is excessively released, which may change the structure of the positive electrode, and too much lithium may be released into the negative electrode, which may easily cause lithium deposition on the surface of the negative electrode, and when the voltage reaches 4.5 V or higher, the electrolyte decomposes to produce a large amount of gas. All of the above may cause an explosion.

External short circuit

External short circuit may be caused by improper operation or misuse. Due to external short circuit, the battery discharge current is very large, which will cause the battery core to heat up. The high temperature will cause the diaphragm inside the battery core to shrink or completely deteriorate, causing internal short circuit and thus exploding. .

The negative electrode with insufficient negative electrode capacity cannot contain the positive and negative poles. The pairing error is negative. When the negative pressure is pressed, the negative electrode particles are negative, the negative electrode, the negative electrode, the negative spot, the negative electrode, the negative electrode, the negative electrode, the negative electrode, the negative coating, the uneven positive electrode, the tail, the stack, the positive electrode coating. The cloth unevenness positive electrode dressing amount is too large, the positive and negative electrode agitation is uneven, the negative electrode material is low, the positive electrode material capacity is high, and the negative electrode capacity is insufficient.

Excessive moisture content of the station seal is too slow, moisture absorption and aging, moisture absorption, electrolyte moisture content is too large, before the injection, baking, unbaked or moisture absorption, assembly, baking, non-drying, coating, when the positive electrode is not dried, the moisture absorption of the positive electrode is insufficient.

The internal short-circuit station paste bottom glue is not completely wrapped around the bottom high-temperature adhesive tape to cover the negative electrode. The upper glue position is not too high. The temperature is too high. The diaphragm is laser-shorted. The short-circuit cell is not detected. The assembly micro-short-circuit cell is under-assembled and short-circuited. The core is not detected when the flattening pressure is too large. The diaphragm paper has a rounded hole. The negative electrode is not flattened. The burr is positive and negative, the small piece is burr, the positive and negative are divided into small pieces, the negative and negative pieces are cut, and the burr is short-circuited.

When the charger is overcharged, the voltage of the charger is too large. When the voltage of the charger is too large, the voltage of the individual point is too large. When the current is set too large, the capacity of the battery is insufficient. The pre-filled cabinet is too large. The current is too large.

External short circuit possible station protection circuit board failure when the user is using the positive and negative short-circuit batteries. The battery is not ignited during the turn-around process, causing the positive and negative contacts to be externally short-circuited.

Sum up all related station must strengthen control. Security is the most important of the capabilities. When in conflict with other requirements, security is prioritized.

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