Some basic knowledge of lithium battery explosion

Basic knowledge of the explosion

The phenomenon that a substance changes rapidly from one state to another, and instantaneously releases a large amount of energy in the form of mechanical work, called an explosion.

During the explosion, the surrounding objects are destructive due to the sharp rise in pressure.

The explosion is characterized by destructive forces, explosive sounds and shock waves.

Cause category of the explosion

Insufficient negative electrode capacity

When the capacity of the negative electrode portion opposite to the positive electrode portion 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 is deposited on the surface of the negative electrode to form a protruding "branch". Crystal, and the next time it is charged, this protruding part is more likely to cause lithium to precipitate. After several tens to hundreds of cycles of charge and discharge, the "dendrites" will grow up, and finally pierce the diaphragm paper, causing a short circuit 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 When 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.

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 heat of the battery core. The high temperature will cause the diaphragm inside the battery core to shrink or completely damage, resulting in internal short circuit and explosion.

Station with insufficient anode capacity

The negative pole can't hold the positive pole

Positive and negative binning pairing error

When the negative electrode is pressed, it is crushed

Negative electrode particle

Negative electrode foil

Negative cathode pit

Negative electrode scratch

Negative smear

Negative coating of the negative electrode

Positive head tail pile

Uneven coating of positive electrode

The amount of positive electrode dressing is too large

Positive and negative stirring unevenly

Negative anode incoming capacity is low

Positive electrode feed capacity is high

Station with excessive moisture content

The seal is too slow to absorb moisture

Absorb moisture as it ages

Excessive electrolyte moisture content

bake before drying, no drying or moisture absorption

Not baked during assembly baking

Positive and negative electrodes are not dried during coating

Moisture absorption when the positive electrode is glued

Insufficient positive baking

Internal short circuit station

The bottom glue is not completely wrapped around the bottom

High temperature adhesive tape wraps the negative ear

The upper glue is not in the wrong position.

The temperature is too high during baking to dry the diaphragm

Laser welding short circuit cell is not detected

Assembling micro short circuit cell downstream

Assembly short-circuit cells are not detected

Too much pressure when crushing

Diaphragm paper with blisters

Wound winding

The negative electrode is not flattened and has burrs

Positive and negative poles

Positive and negative electrodes are separated by small pieces

Positive and negative cut burrs

Overcharge possible station

The charger voltage is too large when the user is using

Individual point voltage is too large during detection

The current setting is too large during detection

Insufficient battery capacity

Pre-filled cabinets have excessive current at individual points

The current setting is too large when pre-charging

External short circuit possible station

Protection circuit board failure

The user is shorted between positive and negative when using

The battery core is ignited during the turnaround

The upper core is not right, causing positive and negative contact

All in all:

All relevant stations must be strengthened.

Safety is the most important of all performances.

Prioritize security when conflicting with other requirements.

The page contains the contents of the machine translation.