In recent years, there has been an increasing number of accidents involving injuries and fatalities caused by lithium-ion battery explosions. What are the main reasons for this? The reasons are as follows:
Insufficient negative electrode capacity
When the capacity of the negative electrode opposite the positive electrode is insufficient or non-existent, some 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, forming protruding dendrites.
During the next charge, this protrusion is more likely to cause lithium deposition. After dozens to hundreds of charge-discharge cycles, the dendrites will grow and eventually pierce the separator paper, causing a short circuit inside.
When a battery cell discharges rapidly, it generates a large amount of heat, which burns the separator and causes a larger short circuit. The high temperature causes the electrolyte to decompose into gas, and the negative electrode carbon and separator paper to burn, resulting in excessive internal pressure. When the battery cell's casing cannot withstand this pressure, the battery cell will explode.
Battery with excessive moisture content
Moisture can react with the electrolyte in the battery cell to produce gas. During charging, it can react with the generated lithium to form lithium oxide, causing capacity loss in the battery cell and making it prone to overcharging and gas generation. Moisture has a low decomposition voltage, so it easily decomposes and generates gas during charging. When this series of generated gases increases the internal pressure of the battery cell, the battery cell will explode when the outer casing cannot withstand it.
Internal short circuit
Due to an internal short circuit, the battery cell discharges a large current, generating a lot of heat that burns the diaphragm, causing an even larger short circuit. This results in the battery cell reaching high temperatures, causing the electrolyte to decompose into gas and creating excessive internal pressure. When the battery cell's casing can no longer withstand this pressure, the battery cell will explode.
upper glue
During laser welding, heat is conducted through the shell to the positive electrode tab, causing the positive electrode tab to reach a high temperature. If the upper adhesive tape does not separate the positive electrode tab from the diaphragm, the hot positive electrode tab will cause the diaphragm paper to burn or shrink, resulting in an internal short circuit and an explosion.
High-temperature adhesive tape wrapped around the negative electrode ear
When the customer is spot welding the negative electrode tab, heat is conducted to the negative electrode tab. If the high-temperature adhesive tape is not properly applied, the heat on the negative electrode tab will burn the diaphragm, causing an internal short circuit and potentially leading to an explosion.
The adhesive on the bottom did not completely cover the bottom.
When customers spot weld the bottom aluminum-nickel composite strip, a lot of heat will be generated on the bottom shell wall, which will conduct heat to the bottom of the electrode core. If the high-temperature adhesive tape does not completely cover the diaphragm, it will burn the diaphragm, causing an internal short circuit and an explosion.
