On May 11th, some big Vs were involved in spreading rumors and smearing Huawei in relation to the Shanxi Wenjie M7 accident. The official response to the entire incident followed shortly after.
According to Wenjie's official statement, during the M7 Plus accident, the vehicle collided with a road maintenance vehicle in the front at a speed of 115km/h. The protruding beam-like hard structure at the rear of the front vehicle severely intruded into the left upper front compartment and passenger compartment of the accident vehicle.
This led to severe damage to the front compartment and passenger compartment, with the wiring harness being instantly severed. The front compartment was ignited by high-temperature components or a short-circuit spark from the wiring harness, starting the fire on the left side of the front compartment and spreading to the entire vehicle, while the power battery pack did not self-ignite.
This incident sparked widespread discussion among netizens: Why do new energy vehicles catch fire? And why are they difficult to extinguish?
Professionals have indicated that thermal runaway in batteries is related to their chemical properties. The working principle of lithium batteries can be simply understood as the movement of lithium ions between the positive and negative electrodes for charging and discharging. Since lithium is a reactive metal, this inherently makes lithium batteries prone to combustion and explosion.
As for the causes of fires, most accidents involving new energy vehicles can be categorized into two main types. One is internal factors, such as poor manufacturing processes leading to impurities or burrs inside the battery, as well as battery aging, which can result in short circuits.
The other type is external factors, like collisions and high temperatures, which often lead to thermal runaway in new energy vehicles involved in major traffic accidents.
When a lithium battery undergoes thermal runaway, it continues to generate heat and produce a large amount of flammable mixed gases containing hydrogen, methane, ethane, and more. If the internal chemical reactions persist and reignite after the external flames are extinguished, recurrent combustion is likely to occur.
Furthermore, due to the confined and compact structure of lithium-ion batteries, in the event of a safety valve failure, the accumulated energy is sufficient to trigger an explosion, making it challenging to extinguish once ignited.
Experts also point out that when a lithium battery catches fire, it often involves ongoing chemical reactions. Cooling from the outside cannot rapidly reduce the temperature to an inactive level, making it prone to reignition. The safe upper limit for the operating temperature of lithium batteries is only 45 degrees Celsius.
Moreover, after long-term, high-capacity, and high-power fast charging, there is a possibility of the formation of "lithium dendrites" during the lithium ion reduction process.
Accumulating over time, these crystals may eventually penetrate the separator between the positive and negative electrodes, causing a short circuit and triggering thermal runaway. "The overcharging process actually makes lithium ions more active, posing a higher risk compared to slow charging."
Zhang Hong, a member of the Expert Committee of the China Automobile Circulation Association, emphasized that preventing battery safety risks requires stringent standards, collaborative efforts from manufacturers, increased consumer awareness, and the cultivation of safe driving habits to minimize the risk of spontaneous combustion.
Preventing and reducing the risk of thermal runaway in new energy vehicles requires collective efforts from various parties. "Enterprises have an unshakable responsibility, not only automotive companies but also battery manufacturers. Ensuring quality control is paramount, and in terms of promotion and consumer education, caution should be exercised rather than trying to cover up incidents."
Of course, experts also acknowledge that security issues are an inevitable phenomenon in the development of new technologies and should not be ignored.
