Summary of causes of lithium battery explosion

by:CTECHi     2021-07-11

Category of the cause of the explosion: Insufficient negative electrode capacity, excessive moisture content, internal short-circuit protection circuit aging failure, overcharge and over-discharge, external short circuit, external extrusion, and violent collision. Insufficient negative electrode capacity When the negative electrode capacity opposite to the positive electrode part is insufficient, or When there is no capacity at all, part or all of the lithium produced during charging cannot be inserted into the interlayer structure of the negative electrode graphite, and will precipitate on the surface of the negative electrode to form protruding “dendrites”. The protruding part will be the next time it is charged. It is easier to cause the precipitation of lithium. After tens to hundreds of cycles of charging and discharging, the 'dendrites' will grow up, and will eventually pierce the diaphragm paper, causing internal short circuits. The battery core discharges rapidly, generating a lot of heat, burning the diaphragm, and causing a greater short circuit. High temperature will decompose the electrolyte into gas, and the negative electrode carbon and diaphragm paper will burn, resulting in excessive internal pressure. When the outer shell of the battery cell cannot When subjected to this pressure, the battery cell will explode. If the moisture content is too high, the moisture can react with the electrolyte in the battery cell to produce gas. When charging, it can react with the generated lithium to generate lithium oxide, which causes the capacity of the battery cell to be lost, and it is easy to overcharge the battery to generate gas. , The decomposition voltage of water is low, and it is easy to decompose to generate gas when charging. When this series of generated gas will increase the internal pressure of the battery, when the outer shell of the battery cannot withstand it, the battery will explode. Internal short circuit due to internal short-circuit phenomenon, large current discharge of the battery cell generates a lot of heat, burns the diaphragm, and causes a greater short-circuit phenomenon, so that the battery cell will generate high temperature, decompose the electrolyte into gas, and cause excessive internal pressure. When the shell of the battery cell cannot withstand this pressure, the battery cell will explode. When the upper adhesive is laser welded, the heat is conducted to the positive ear through the shell, making the temperature of the positive ear high. If the upper adhesive paper does not separate the positive ear and the diaphragm, the hot positive ear will burn out or shrink the diaphragm paper, causing the inside Short-circuit, and form an explosion. When the customer spot welding the negative ear with high temperature adhesive paper wraps the negative ear, the heat is transferred to the negative ear. If the high temperature adhesive paper is not properly attached, the heat on the negative ear will burn the diaphragm, cause an internal short circuit, and cause an explosion. The bottom glue does not completely cover the bottom. When customers spot welding at the bottom aluminum-nickel composite tape, a large amount of heat will be generated on the bottom shell wall, which will conduct the bottom of the pole core. If the high-temperature adhesive paper does not completely cover the diaphragm, it will burn the diaphragm. , Causing an internal short circuit, causing an explosion. When the overcharge core is overcharged, the excessive release of lithium in the positive electrode will change the structure of the positive electrode. If too much lithium is released, it is easy to be unable to be inserted into the negative electrode, and it is also easy to cause lithium deposition on the surface of the negative electrode. Moreover, when the voltage reaches 4.5V or more , The electrolyte will decompose to produce a large amount of gas. All of the above may cause an explosion. External short-circuit The external short-circuit may be caused by improper operation or misuse. Due to the external short-circuit, the battery discharge current is large, which will cause the battery core to heat up, and the high temperature will shrink or completely destroy the diaphragm inside the battery cell, causing an internal short circuit. It exploded. Work station with insufficient negative capacity. The negative electrode cannot cover the positive and negative poles. The positive and negative poles are mismatched. The negative electrode particles are crushed when the negative electrode is pressed. The negative electrode is exposed. The negative electrode pits are scratched. The negative electrode is not evenly coated. Uneven distribution of positive electrode dressing is too large, uneven mixing of positive and negative electrodes, low incoming material capacity of negative electrode, high incoming material capacity of negative electrode, insufficient capacity of negative electrode, station with too much water content, sealing is too slow and it absorbs moisture when aging electrolyte moisture The content is too large, it is not baked before the liquid is injected, or it is not dried during assembly, when the positive and negative electrodes are not dried during the baking, the positive and negative electrodes are not dried when the positive electrode is glued, the positive electrode is not baked sufficiently, the moisture content is too high, the internal short circuit The bottom glue of the station sticker does not completely cover the bottom of the high temperature glue paper to cover the negative ear. The upper glue position is wrong. The temperature is too high and the diaphragm is damaged. The laser welding short circuit cell is not detected. The assembly of the micro short circuit cell is not detected. The downstream assembly of the short circuit cell is not detected. There is too much pressure during flattening. Diaphragm paper has blisters. The negative electrode is riveted and welded. There are burrs. The positive and negative electrodes are divided into small pieces. The positive and negative electrodes are divided into small pieces. Positive and negative cutting. ** The internal short circuit of the burr may cause overcharge. When the charger voltage is too large when used by a user, the voltage of individual points is too large during detection. The current setting is too large during detection. The cell capacity is insufficient. The current of individual points in the pre-charging cabinet is too large. Circuit board failure. When the user uses the positive and negative poles, the short-circuited cells are not properly aligned during the turnover process, causing the positive and negative poles to contact the external short circuit. Summary All related stations must be controlled. Safety is the most important of all performances. When conflicts with other requirements, safety is the priority.

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