Causes of lithium-ion battery explosions
1. Overcharge explosion
If the protection circuit or the detection cabinet malfunctions, causing the charging voltage to exceed 5V, the electrolyte will decompose, a violent reaction will occur inside the battery, the internal pressure of the battery will rise rapidly, and the battery will explode.
2. Overcurrent explosion
If the protection circuit or the detection cabinet malfunctions, the charging current may be too large, causing lithium ions to not have time to embed and instead form lithium metal on the electrode surface. This lithium metal penetrates the separator, causing a direct short circuit between the positive and negative electrodes and resulting in an explosion.
3. Explosion during ultrasonic welding of plastic casing
During ultrasonic welding of the plastic casing, due to equipment malfunctions, the ultrasonic energy was transferred to the battery cell. The high ultrasonic energy caused the internal separator of the battery to melt, resulting in a direct short circuit between the positive and negative electrodes and an explosion.
4. Explosion during spot welding
Excessive current during spot welding caused a severe internal short circuit, leading to an explosion. Additionally, the positive electrode connector was directly connected to the negative electrode during spot welding, causing a direct short circuit between the positive and negative electrodes, which resulted in an explosion.
5. Over-explosion explosion
Over-discharge or overcurrent discharge (above 3C) of a battery can easily cause the copper foil on the negative electrode to dissolve and deposit on the separator, resulting in a direct short circuit between the positive and negative electrodes and an explosion.
6. Explosion upon vibration and drop
When a battery cell is subjected to severe vibration or a drop, the internal electrode plates may become misaligned, causing a direct and serious short circuit and resulting in an explosion (this is rare).
Are lithium-ion batteries really more prone to exploding than lead-acid batteries?
Both lithium-ion and lead-acid batteries are designed with safety valves to prevent abnormal increases in internal pressure. Even if an abnormal situation such as a short circuit occurs inside the battery, the internal pressure will be released in time, preventing major risks.
From a battery safety design perspective, both qualified lithium-ion and lead-acid batteries can fully guarantee user safety, with no significant difference in safety. However, due to the large number of low-end small electric vehicles and scooters on the market, many of which use lower-quality lithium-ion batteries, accidents are relatively more likely to occur, creating a misconception among consumers that lithium-ion batteries are unsafe. In terms of battery structure, current lithium-ion battery packs are primarily packaged with 18650 cells, while lead-acid batteries are generally well-sealed and maintenance-free. If the internal pressure is too high and the safety valve malfunctions, the risk factors for both are essentially the same.
