Sep 09, 2019 Pageview:792
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.
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