3s 11.1v 2200mah process design and thermal runaway

Recently, Tesla, Weilai and BYD have caught fire one after another, pushing the safety of power batteries to the forefront.
Here I share an article on the influencing factors of 3s 11.1v 2200mah security summarized by CNHL, and I hope everyone can criticize and correct it.
The safety of 3s 11.1v 2200mah is one of the most concerned issues for power batteries. The safety of 3s 11.1v 2200mah has a lot to do with the production process of the battery.
The production process of 3s 11.1v 2200mah is very complicated, and even with strict control, metal impurities or burrs in the production process cannot be completely avoided. If impurities, burrs or dendrites appear inside the 3s 11.1v 2200mah, after amplification and deterioration, the conductivity of the 3s 11.1v 2200mah will increase, the temperature will rise, and the heat generated by chemical reactions and discharge heating will continue to accumulate, which may eventually cause the 3s 11.1v 2200mah. of thermal runaway.

3s 11.1v 2200mah negative electrode capacity is insufficient

When the capacity of the negative electrode opposite to the positive electrode is insufficient, or has no capacity at all, some or all of the lithium generated during 3s 11.1v 2200mah charging cannot be inserted into the interlayer structure of the negative electrode graphite, and will be deposited in the 3s 11.1v 2200mah negative electrode On the surface of the battery, a protruding "dendrite" is formed, and this protruding part is more likely to cause lithium precipitation when charging the next time.

After tens to hundreds of cycles of charge and discharge, the "dendrite" will grow and eventually sting Wear 3s 11.1v 2200mah separator paper to create a short circuit inside. The battery cell is rapidly discharged, generating a lot of heat, burning out the diaphragm, and causing a larger 3s 11.1v 2200mah short circuit. High temperature will decompose the electrolyte into gas, and the negative carbon and diaphragm paper will burn, resulting in excessive internal pressure. When the shell of the core cannot withstand this pressure, the 3s 11.1v 2200mah battery will explode.

3s 11.1v 2200mah water content is too high

Moisture can react with the electrolyte in the 3s 11.1v 2200mah battery to produce gas. When charging, it can react with the lithium generated by the 3s 11.1v 2200mah to generate lithium oxide, which will cause the capacity loss of the battery and easily overcharge the battery. As for the generated gas, the decomposition voltage of water is low, and it is easy to decompose the generated gas when charging. When this series of generated gases will increase the internal pressure of the 3s 11.1v 2200mah battery, when the outer shell of the battery cannot withstand it, The battery will explode.

3s 11.1v 2200mah internal short circuit

Due to the short circuit phenomenon inside the 3s 11.1v 2200mah, the high current discharge of the battery cell generates a lot of heat, burns the diaphragm, and causes a larger short circuit phenomenon, so that the battery core will generate high temperature, the electrolyte will be decomposed into gas, causing 3s The internal pressure of 11.1v 2200mah is too large. When the outer casing of the cell cannot withstand this pressure, the cell will explode.
During laser welding, the heat is conducted to the 3s 11.1v 2200mah positive lug through the shell, which makes the temperature of the positive lug high. If the upper tape does not separate the positive lug and the diaphragm, the hot positive lug will burn or shrink the diaphragm paper. Caused 3s 11.1v 2200mah internal short circuit and exploded.

High temperature tape to wrap 3s 11.1v 2200mah negative lug

During spot welding of the negative lug, the heat is conducted to the negative lug. If the high temperature adhesive tape is not properly attached, the heat on the negative lug of the 3s 11.1v 2200mah will burn the diaphragm, causing an internal short circuit and an explosion.

The bottom glue is not fully covered with the bottom

When the customer spot welds the aluminum-nickel composite belt at the bottom, a lot of heat will be generated on the bottom shell wall, and the bottom of the conduction pole core will be burned out if the high-temperature adhesive tape does not completely wrap the diaphragm, causing an internal short circuit and an explosion.

3s 11.1v 2200mah overcharge

When the cell is overcharged, the excessive release of lithium from the 3s 11.1v 2200mah positive electrode will change the structure of the positive electrode, and too much lithium is easily unable to be inserted into the negative electrode, and it is also easy to cause lithium precipitation on the surface of the 3s 11.1v 2200mah negative electrode. When the voltage reaches above 4.5V, the electrolyte will decompose to produce a large amount of gas. All of the above may cause an explosion.

3s 11.1v 2200mah external short circuit

External short circuit may be caused by improper operation or misuse. Due to external short circuit, the discharge current of 3s 11.1v 2200mah is very large, which will make the cell heat up. v 2200mah shorted internally and exploded.
3s 11.1v 2200mah station with insufficient negative capacity
The negative electrode cannot cover the positive electrode, the 3s 11.1v 2200mah positive and negative poles are incorrectly paired, the negative electrode is pressed to death, the negative electrode particle, the negative electrode exposed foil,the negative electrode pit, the negative electrode scratch, the negative negative mark, the negative electrode coating is uneven, 3s 11.1v 2200mah positive electrode head and tail are stacked, the positive electrode is unevenly coated, the amount of positive electrode dressing is too large, the positive and negative electrodes of 3s 11.1v 2200mah are not evenly stirred, the negative electrode incoming capacity is low, the positive electrode incoming capacity is high, and the negative electrode capacity is insufficient .

3s 11.1v 2200mah Workstation with excessive moisture content

The sealing is too slow to absorb moisture, the moisture absorbs during aging, the moisture content of the electrolyte is too large, the baking is not dried or moisture absorbed before the injection, the assembly is not dried during the baking, and the positive and negative electrodes are not dried during coating. , When the positive electrode is glued, it absorbs moisture, the positive electrode is not fully baked, and the moisture content is too high.

3s 11.1v 2200mah internal short circuit station

The bottom of the 3s 11.1v 2200mah is not completely covered by the bottom glue, the high temperature tape wraps the negative terminal, the upper glue is in the wrong position, the temperature is too high during baking, the diaphragm is damaged, the laser welding short-circuit cell is not detected, and the micro-short-circuit cell is assembled Downflow, the short-circuited cell was not detected, the pressure was too high when flattened, the 3s 11.1v 2200mah diaphragm paper has blisters, the winding is uneven, the negative electrode riveting welding is not flat, there are burrs, the positive and negative electrodes are divided into small burrs, positive and negative Extremely small pieces are dropped, and there is an internal short circuit.

3s 11.1v 2200mah overcharge possible station

The voltage of the charger is too large when the user is using it, the voltage of individual points is too large during detection, the current setting of 3s 11.1v 2200mah is too large during detection, the capacity of the battery cells is insufficient, the current of individual points in the pre-charging cabinet is too large, and the current setting during pre-charging is too large, 3s 11.1v 2200mah overcharge.

Possible stations for external short circuit

The 3s 11.1v 2200mah protection circuit board fails. When the user is in use, the positive and negative electrodes are short-circuited. The battery cells ignite during the turnover process.
Well, the above is the whole content of the 3s 11.1v 2200mah process design and thermal runaway brought by CNHL. The 3s 11.1v 2200mah negative electrode capacity is insufficient and the negative electrode capacity is insufficient and other reasons will cause the 3s 11.1v 2200mah thermal runaway phenomenon, and more More information about 3s 11.1v 2200mah can be found in our previous articles:
How much do you know about drone lithium batteries?
Development and Structure of Lithium Batteries