A number of traffic accidents recently have once again drawn widespread attention to the safety of new energy vehicles.
Fires after collisions of new energy vehicles have always been an invisible wall between car companies and consumers. Although car companies have repeatedly emphasized the safety performance of power batteries and even used needle puncture tests to demonstrate battery reliability, at the same time, the frequent fires in traffic accidents have made consumers question: Are new energy vehicles more likely to catch fire after collisions? Can such a situation be avoided?
Zhang Hong, a member of the Expert Committee of the China Automobile Dealers Association, said in an interview with The Paper that new energy vehicles equipped with lithium batteries do have problems such as fire and spontaneous combustion after collisions, and that fires in new energy vehicles are more difficult to extinguish and more dangerous, which must be highly valued and vigilant by all parties involved in research and development, manufacturing, sales and use.
Many industry insiders told The Paper that safety issues are inevitable in the development of new technologies and should not be abandoned because of fear.
Are new energy vehicles more likely to catch fire?
At the Electric Vehicle Hundred People Conference held in April this year, Ouyang Minggao, vice chairman of the China Electric Vehicle Hundred People Conference and academician of the Chinese Academy of Sciences, said that data from the National Fire Rescue Bureau showed that among the vehicles that spontaneously caught fire in the first quarter of 2023, there were 18,360 fuel vehicles and 640 new energy vehicles. From the perspective of the fire rate, 18,360 fuel vehicles divided by the total number of fuel vehicles of 317.71 million vehicles is 0.58 per 10,000; 640 new energy vehicles divided by the number of new energy vehicles of 14.452 million vehicles is 0.44 per 10,000, and the proportion of new energy vehicles is slightly lower.
He pointed out that such data is the same in the United States. Tesla did not recall any vehicles in the US market due to fire risks from 2018 to 2023, but all fuel vehicle manufacturers have.
At the same time, he also emphasized that “of course, eight new energy vehicles burn every day in the Chinese market, which is not a small number. This needs to be continuously reduced through technological innovation.”
Since the data clearly shows that the spontaneous combustion of new energy vehicles is not higher than that of fuel vehicles, then why does it seem that all the accidents in public opinion are new energy vehicle fires?
On the one hand, as a new product, new energy vehicles are more concerned by the society than fuel vehicles that have existed for hundreds of years; on the other hand, it is worth pointing out that the consequences of new energy vehicle fires are often much more serious than those of fuel vehicles.
It is not difficult to find from past news reports that in new energy vehicle fire accidents, the fire often spreads rapidly throughout the vehicle within a few minutes, making it extremely difficult to extinguish, and even accompanied by explosions during the combustion process. And this is not a special case of a few brands or models.
Why do new energy vehicles catch fire? And why are they difficult to extinguish?
Li Te (pseudonym), an automotive industry practitioner, told the reporter of The Paper that battery thermal runaway is related to its 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 to charge and discharge. Lithium is an active metal, which in itself determines the flammable and explosive properties of lithium batteries.
As for the cause of the fire, Li Te said that most new energy vehicle fire accidents can be mainly summarized into two categories, “One is the internal reason, the production and manufacturing process is not good, such as impurities and burrs in the battery, and the battery is aging, which may cause short circuits; the other is the external reason, that is, collisions, high temperatures, etc., which is why major traffic accidents involving new energy vehicles often lead to thermal runaway of vehicles.”
At present, mainstream new energy vehicles are generally lithium-ion batteries. There are two common types, one is a ternary polymer lithium battery containing three elements of cobalt, manganese and nickel, that is, a ternary lithium battery, and the other is a lithium iron phosphate battery.
The energy density of ternary lithium batteries is greater, that is, at the same weight, ternary lithium batteries can provide more power for the car, which is conducive to improving the vehicle’s endurance.
So, why do lithium batteries often explode after catching fire?
When a lithium battery experiences thermal runaway, it will continue to release heat and produce a large amount of combustible mixed gases containing hydrogen, methane, ethane, etc. If the internal chemical reaction continues, it is easy to re-ignite after the external open fire is extinguished. Coupled with the structural characteristics of the small and enclosed space of lithium-ion batteries, if the safety valve fails, the backlog of energy is enough to cause an explosion.
In addition, many netizens said on social media that it is impossible to extinguish the fire of the power battery of new energy vehicles. This has also become the “death point” of new energy vehicles.
In this regard, Li Te said “partially correct”. He explained that when lithium batteries catch fire, they are often accompanied by chemical reactions. The chemical reaction is continuous. It is impossible to quickly cool down to its inactive temperature from the outside, and it is very easy to re-ignite. The safest upper limit of the operating temperature of lithium batteries is only 45 degrees.
“In addition, the compounds in the ternary lithium battery contain oxygen. After heating, it is easier to release oxygen molecules. Then the combustibles and combustion-supporting materials are all complete, and the commonly used fire-extinguishing method of blocking oxygen is basically useless.” He added.
Can the fire be avoided?
Many industry insiders said that to solve the thermal runaway of new energy vehicles from the root, it is necessary to start from technological innovation, but the current technology has not yet reached the level of completely eliminating thermal runaway.
Zhang Hong said that the safety of power batteries is a complex systemic problem, covering many factors such as battery material selection, manufacturing process, safety testing and daily use. It should be noted that all battery manufacturers are working hard to improve the safety performance of power batteries. For example, through intelligence, strengthening the battery cooling system or heat dissipation system, increasing the research and development efforts and popularization and application speed of solid-state batteries to replace lithium batteries.
He also mentioned that the level of battery detection technology is also rapidly improving. At present, it has reached a time much shorter than fast charging. It can detect multiple parameters including energy consumption, providing early warning signals to understand whether the power battery is safe.
“As we all know, in many cases, science and technology are developed to solve technical problems and pain points. The problem of power battery fire caused by factors such as leakage of aging electrolyte, heat, scratches or collisions will also be solved as soon as possible with scientific and technological breakthroughs.” Zhang Hong added.
Feng Tian (pseudonym), a practitioner in the lithium battery industry, believes that the current technology route can replace lithium batteries. On the one hand, solid-state battery technology, which is being gradually conquered by major companies, is expected to greatly improve the safety of new energy vehicles; on the other hand, the battery replacement technology is becoming popular, which can also improve the safety of battery use. Feng Tian introduced that during the supercharging process, after long-term, large-capacity, high-power fast charging, lithium batteries may produce “lithium dendrites” during the lithium ion reduction process. Crystals accumulate over time and may eventually pierce the positive and negative electrodes, causing a short circuit between the positive and negative electrodes of the battery cell, thus causing thermal runaway. “The supercharging process actually makes lithium ions more active, which is inherently more risky than slow charging.”
In addition, Feng Tian said that the battery swap mode provides a good channel for regular battery health checks. “As far as we know, battery swap stations can often detect battery bumps or aging problems, which the car owners or operating drivers are not aware of at all.”
However, Feng Tian also said that the battery swap mode still uses lithium batteries, which essentially cannot prevent the occurrence of fire incidents, especially thermal runaway caused by external factors such as car accidents. “At present, the so-called ‘ultimate solution’ that the world is more optimistic about is still solid-state batteries. This is also the direction that automobile powers such as Japan are desperately researching, trying to surpass Chinese new energy vehicles in the solid-state battery track.”
Industry insiders call for not throwing food out with the bathwater
In Zhang Hong’s view, under the current technical conditions, preventing battery safety risks requires starting from multiple angles.
From the perspective of the enterprise, he mentioned that in terms of hardware, under the guidance of relevant national standards, battery manufacturers and vehicle manufacturers should be more clear about the goal of power battery safety. In the design stage, they should ensure that the battery can remain stable under various extreme conditions and avoid dangerous situations such as thermal runaway; from the software side, the battery management system BMS should be used to protect the safety of power batteries. In addition, it is also necessary to configure an efficient heat dissipation system for the battery to ensure that the battery can maintain normal operation in a high temperature environment and will not cause safety problems such as thermal runaway.
From the consumer level, Zhang Hong believes that safety awareness should be improved, and the various performance and configurations of the new energy vehicles purchased should be understood, especially the characteristics of emerging intelligent electric vehicle equipment. Actively develop safe car use habits, such as choosing not to expose to the sun when parking, and taking intervals to rest during long journeys to minimize the hidden dangers of spontaneous combustion.
He said that from the regulatory level, the role of national mandatory standards should be further played, and the formulation and revision of power battery safety review standards should be accelerated, requiring all parties involved in manufacturing, sales and driving to strictly abide by relevant laws and regulations to build a solid bottom line for power battery safety.
Industry insider Li Ze (pseudonym) also said that under the current technical conditions, preventing and reducing the risk of thermal runaway of new energy vehicles must be a joint effort of multiple parties. He especially pointed out that “enterprises have an unshirkable responsibility, not only car companies, but also battery companies. Quality control is the first priority. In terms of publicity and consumer education, they should be more cautious, rather than confusing concepts and just want to keep things quiet when something goes wrong.”
In addition, Li Ze also said that more data should be shared between power battery companies and car companies. He revealed that at present, the sharing between companies is insufficient, and each has its own database. Companies do not open up on the grounds of “trade secrets”, which is not conducive to the comprehensive management of batteries.
However, Li Ze also said that technology and supervision are gradually advancing. At present, there are relevant regulations such as “Test Specifications for Thermal Diffusion Member Protection of Power Battery Systems for Electric Vehicles” and “Safety Requirements and Test Methods for Power Batteries for Electric Vehicles”. It is believed that at the moment when new energy vehicles are already in parallel with fuel vehicles, more and more specific regulations will be introduced, including connecting corporate data.
Zhang Hong has also repeatedly stressed that we should not be afraid of new energy vehicles and should have full confidence in their sustained and stable development.