Recent traffic accidents have once again brought widespread attention to the safety issues of electric vehicles.
The issue of electric vehicles catching fire after collisions has always been a hidden barrier between car manufacturers and consumers. Despite car manufacturers repeatedly emphasizing the safety performance of the power battery, even resorting to nail puncture tests to demonstrate the reliability of the battery, the frequent occurrence of fires in traffic accidents has led consumers to question: Are electric vehicles more likely to catch fire after a collision? Can such situations be avoided?
Zhang Hong, a member of the Expert Committee of the China Automobile Circulation Association, mentioned in an interview with The Paper that problems such as fires and spontaneous combustion after collisions do exist in electric vehicles equipped with lithium batteries. Moreover, fires in electric vehicles are more difficult to extinguish and pose higher risks, requiring high attention and vigilance from all parties involved in research and development, manufacturing, sales, and usage.
Several industry insiders told The Paper that safety issues are inevitable in the process of technological development and cannot be ignored.
Are electric vehicles more prone to catching fire?
At the Electric Vehicle Hundred-Person Conference held in April this year, Ouyang Minggao, Vice Chairman of the Electric Vehicle Hundred-Person Conference and Academician of the Chinese Academy of Sciences, stated that according to data from the National Fire and Rescue Bureau, in the first quarter of 2023, there were 18,360 cases of combustion in gasoline vehicles and 640 cases in electric vehicles. In terms of the fire rate, the 18,360 gasoline vehicles divided by the total number of gasoline vehicles of 317.71 million is 0.58 per ten thousand, while the 640 electric vehicles divided by the total number of electric vehicles of 14.452 million is 0.44 per ten thousand, slightly lower for electric vehicles.
He pointed out that similar data can be seen in the United States. Tesla did not recall any vehicles due to fire risks in the U.S. market from 2018 to 2023, while gasoline car manufacturers all had recalls.
He also emphasized, "Of course, it is not insignificant that eight electric vehicles catch fire every day in the Chinese market, and this needs to be continuously reduced through technological innovation."
Since the data clearly shows that incidents of electric vehicles catching fire are not higher than gasoline vehicles, why does it seem like all the accidents reported in the media are about electric vehicles catching fire?
On one hand, as a new product, electric vehicles attract more social attention compared to gasoline vehicles that have been around for over a hundred years. On the other hand, it is worth noting that the consequences of electric vehicle fires are often much more severe than those of gasoline vehicle fires.
From past news reports, it is evident that in electric vehicle fire incidents, the fire often spreads rapidly throughout the vehicle within minutes, making it extremely difficult to extinguish, sometimes even leading to explosions. This is not limited to specific brands or models.
Why do electric vehicles catch fire? And why are they difficult to extinguish?
Li Te (pseudonym), an industry practitioner in the automotive sector, explained to The Paper that thermal runaway of batteries is related to their chemical properties. The working principle of lithium batteries can be simply understood as relying on the movement of lithium ions between the positive and negative electrodes of the battery for charging and discharging. Since lithium is a reactive metal, this inherently makes lithium batteries prone to ignition and explosion.
New energy vehicle lithium batteries, Visual China data image
As for the reasons for fires, Li Te said that most new energy vehicle fires can be categorized into two main types. One is internal reasons, such as poor production processes, impurities or burrs inside the battery, and battery aging, which can lead to short circuits. The other is external reasons, such as collisions, high temperatures, which often result in thermal runaway in new energy vehicles during major traffic accidents.
Currently, mainstream new energy vehicles generally use lithium-ion batteries, with two common types: one is the ternary polymer lithium battery containing cobalt, manganese, and nickel, and the other is the lithium iron phosphate battery.
Ternary lithium batteries have a higher energy density, meaning they can provide more power to vehicles for the same weight, thus improving the vehicle's range.
So, why do lithium batteries often explode after catching fire?
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, etc. If the internal chemical reactions persist and an external flame is extinguished, it can easily reignite. Coupled with the confined space structure of lithium-ion batteries and the failure of safety valves, the accumulated energy can lead to explosions.
In addition, many netizens claim on social media that it is impossible to extinguish the burning of new energy vehicle power batteries. This has become a "fatal flaw" for new energy vehicles.
Regarding this, Li Te stated it is "partially correct." He explained 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 safest operating temperature limit for lithium batteries is only 45 degrees.
"Furthermore, compounds in ternary lithium batteries contain oxygen. When heated, they easily release oxygen molecules, making it difficult for common oxygen-blocking fire suppression methods to be effective," he added.
Can fires be prevented?
Several industry insiders suggest that to fundamentally address the issue of thermal runaway in new energy vehicles, it is necessary to start from technological innovation. However, current technology has not completely eliminated the risk of thermal runaway.
Zhang Hong stated that the safety of power batteries is a complex systemic issue, involving factors such as battery selection, manufacturing processes, safety testing, and daily use. It should be noted that battery manufacturers are striving to enhance the safety performance of power batteries. For example, through intelligence, strengthening battery cooling systems or heat dissipation systems, increasing efforts to develop and popularize solid-state batteries to replace lithium-ion batteries, among others.
He also mentioned that battery testing technology is rapidly advancing. Currently, it can detect multiple parameters, including energy consumption, in a much shorter time than fast charging, providing early warning signals to ensure the safety of power batteries.
"It is well known that in many cases, science and technology develop to solve technical problems and pain points. Issues such as power battery fires caused by factors like aging electrolyte leakage, abrasion, or collisions will be quickly resolved through technological breakthroughs," Zhang Hong added.
Feng Tian, a practitioner in the lithium battery industry, believes that in the current technological roadmap, solid-state battery technology, which major companies are gradually overcoming, holds the potential to significantly enhance the safety of new energy vehicles. Additionally, the emerging battery swapping technology can also improve battery safety.
Feng Tian explained that during supercharging, lithium batteries may develop "lithium dendrites" during the long-term, high-capacity, high-power fast charging process. Over time, these crystals may eventually pierce the separator between the positive and negative electrodes, causing a short circuit and leading to thermal runaway. "The supercharging process makes lithium ions more active, posing a higher risk than slow charging," he said.
Furthermore, Feng Tian stated that the battery swapping model provides a good channel for regular battery check-ups. "According to our understanding, battery swapping stations can often detect battery damage or aging issues that vehicle owners or operators are not aware of."
However, Feng Tian also pointed out that the battery swapping model still uses lithium batteries, which fundamentally does not eliminate the risk of fires, especially those caused by external factors such as accidents. "Currently, the so-called 'ultimate solution' that the world is optimistic about is solid-state batteries. This is also a direction that automotive powerhouses like Japan are vigorously researching to surpass China in the new energy vehicle race."
Industry experts urge not to throw the baby out with the bathwater
In Zhang Hong's view, under current technological conditions, preventing battery safety risks requires a multi-faceted approach.
From an enterprise perspective, he mentioned that under the guidance of relevant national standards, battery manufacturers and vehicle manufacturers should have clearer goals for power battery safety. During the design phase, they should ensure that batteries remain stable under various extreme conditions and do not experience thermal runaway or other dangerous situations. From a software perspective, the Battery Management System (BMS) should safeguard power battery safety. Additionally, efficient cooling systems should be installed to ensure batteries can operate normally even in high-temperature environments, preventing thermal runaway and other safety issues.
From a consumer standpoint, Zhang Hong believes that raising safety awareness is crucial. Consumers should understand the various performance and configurations of the new energy vehicles they purchase, especially the characteristics of emerging intelligent electric vehicle equipment. They should proactively cultivate safe driving habits, such as avoiding parking in direct sunlight, taking breaks during long journeys, and minimizing the risk of spontaneous combustion.
He emphasized that from a regulatory perspective, the role of mandatory national standards should be further enhanced. Accelerating the revision of standards for power battery safety inspections is essential. Manufacturers, sellers, and users should strictly adhere to relevant laws and regulations to establish a solid safety baseline for power batteries. Industry insider Li Ze (pseudonym) also stated that under current technological conditions, preventing and reducing the risk of thermal runaway in new energy vehicles requires joint efforts from multiple parties. He particularly emphasized, "Enterprises have an undeniable responsibility, not only car manufacturers but also battery companies. Ensuring quality control is paramount. In terms of publicity and consumer education, caution should be exercised, rather than confusing concepts and only seeking to cover up issues when they arise."
Furthermore, Li Ze also mentioned that there should be more data sharing between power battery companies and car manufacturers. He revealed that currently, there is insufficient data sharing among companies, each maintaining its own database. Companies cite "commercial secrets" as a reason for not sharing, which hinders comprehensive battery management.
However, Li Ze acknowledged that both technology and regulations are progressing gradually. There are already regulations such as the "Thermal Diffusion Member Protection Test Specification for Power Battery Systems for Electric Vehicles" and the "Safety Requirements and Test Methods for Power Batteries for Electric Vehicles." With the current trend of new energy vehicles running parallel to traditional fuel vehicles, it is believed that more specific regulations, including the sharing of enterprise data, will be introduced.
Zhang Hong has also emphasized multiple times the importance of not neglecting new energy vehicles due to minor setbacks, urging confidence in their continuous and stable development.
