Are new energy vehicles more likely to catch fire than fuel vehicles? How to prevent "burning" before it happens?

Recently, a number of traffic accidents have once again attracted widespread attention to the safety of new energy vehicles.

The fire of new energy vehicles after collision has always been an invisible wall between car companies and consumers. Although car companies have repeatedly emphasized the safety performance of power batteries, and even moved out acupuncture experiments 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 a collision? Can this be avoided?

Zhang Hong, a member of the expert committee of the China Automobile Dealers Association, said in an interview with the surging news reporter that problems such as fire and spontaneous combustion of new energy vehicles equipped with lithium batteries do exist after collision, and the fire of new energy vehicles is more difficult to extinguish and the danger is higher, which must arouse the great attention and vigilance of all parties involved in research and development, manufacturing, sales and use.

A number of industry insiders told The Paper that safety is inevitable in the development of new technologies, and food should not be wasted because of choking.

Are new energy vehicles more likely to catch fire?

At the Electric Vehicle 100 Conference held in April this year, Ouyang Minggao, vice chairman of the China Electric Vehicle 100 Association and academician of the Chinese Academy of Sciences, said that data from the National Fire and Rescue Administration showed that in the first quarter of 2023, 18,360 were fuel vehicles and 640 were new energy vehicles. From the perspective of fire rate, the number of 18,360 fuel vehicles divided by the total number of fuel vehicles is 317.71 million is 0.58 per 10,000, and the 640 new energy vehicles divided by the number of new energy vehicles 14.452 million are equal to 0.44 per 10,000, and the proportion of new energy vehicles is slightly lower.

He noted that such data is the same in the United States. Tesla did not recall any vehicles in the U.S. market from 2018 to 2023 due to fire risks, but all fuel vehicle manufacturers did.

At the same time, he also emphasized, "Of course, there are not many new energy vehicles burned 8 times a day in the Chinese market, which needs to be continuously reduced through scientific and technological innovation." ”

Since the data clearly shows that the spontaneous combustion of new energy vehicles is not higher than that of fuel vehicles, why does it seem that in public opinion, all of them are accidents caused by new energy vehicle fires?

On the one hand, as a new product, new energy vehicles have attracted more social attention than fuel vehicle products that have existed for hundreds of years; On the other hand, it is worth pointing out that the consequences of fire accidents of new energy vehicles are often much more serious than those caused by fires of fuel vehicles.

It is not difficult to find from past news reports that in the fire accident of new energy vehicles, the fire often spreads quickly to the whole vehicle within a few minutes, which is extremely difficult to extinguish, and even accompanied by an explosion during the combustion process. And this is not a special case for a few brands or models.

Why do new energy vehicles catch fire? And why is it so difficult to extinguish?

Li Te (pseudonym), a practitioner in the automotive industry, told the surging news reporter that the thermal runaway of the battery is related to its chemical properties, and the working principle of the lithium battery can be simply understood as relying on lithium ions to move between the positive and negative electrodes of the battery to charge and discharge. And lithium is a reactive metal, which itself determines the flammable and explosive properties of lithium batteries.

Lithium battery for new energy vehicles Visual China data map

As for the cause of the fire, Li Te said that most new energy vehicle fire accidents can be summarized into two categories, "one is internal reasons, the manufacturing process is not good, such as impurities in the battery, burrs, and battery aging, short circuits may occur; One is external causes, that is, collisions, high temperatures, etc., which is why major traffic accidents of new energy vehicles often lead to thermal runaway of vehicles. ”

At present, mainstream new energy vehicles are generally lithium-ion batteries, and there are two common ones, one is a ternary polymer lithium battery containing 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, under the same weight, ternary lithium batteries can provide more power for the car, which is conducive to improving the endurance of the vehicle.

So, why do lithium batteries often explode after they catch fire?

When the lithium battery has thermal runaway, it will continue to release heat and produce a large amount of combustible mixed gas containing hydrogen, methane, ethane, etc., if the internal chemical reaction continues, after the external open flame is extinguished, it is easy to re-ignite. Coupled with the structural characteristics of the narrow and confined space of lithium-ion batteries, the backlog of energy is enough to cause an explosion in the event of a failure of the safety valve.

In addition, many netizens said on social media that the power battery of new energy vehicles cannot be extinguished when burned. This has also become a "dead hole" for new energy vehicles.

In this regard, Litt said that it was "partially correct". He explained that lithium batteries are often accompanied by chemical reactions when they catch fire, and the chemical reaction is continuous, cooling from the outside, which cannot be quickly reduced to its inactive temperature, and is very easy to re-ignite, and 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, and after heating, it is easier to release oxygen molecules, so the combustibles and combustibles are complete, and the commonly used fire extinguishing methods that block oxygen are basically useless." He added.

Can the fire be avoided?

A number of industry insiders said that in order to solve the current thermal runaway of new energy vehicles from the root, we must ultimately 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 issue, 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, strengthen the battery cooling system or heat dissipation system, increase and accelerate the development and popularization of solid-state batteries, so as to replace lithium batteries.

He also mentioned that the level of battery testing technology is also rapidly improving, and it has reached a much shorter time than fast charging, which can detect a number of parameters including energy consumption, so as to provide early warning signals for grasping 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 aging electrolyte leakage, dry heat, scratching or collision and other factors will also be solved as soon as possible with scientific and technological research. Zhang Hong added.

Feng Tian (pseudonym), a practitioner in the lithium battery industry, believes that the current technical route that can replace lithium batteries is, on the one hand, the solid-state battery technology that major enterprises are gradually conquering, which is expected to greatly improve the safety of new energy vehicles; On the other hand, the battery swapping technology that is being popularized can also better improve the safety of battery use.

Feng Tian introduced that in the process of overcharging, after the long-term, large-capacity, high-power fast charging of lithium batteries, the phenomenon of "lithium dendrites" may be produced in the lithium-ion reduction process. The crystals accumulate over time, and may eventually pierce the separator of the positive and negative electrodes, causing a short circuit in the positive and negative electrodes of the cell, thus causing thermal runaway. ”

In addition, Feng Tian said that the battery swap mode provides a good channel for the regular physical examination of the battery, "As far as we know, the battery swap station can often check out the bump or aging of the battery, which is not realized by the owner or the operating driver." ”

However, Feng Tian also said that the battery swap mode uses lithium batteries, which in essence can not prevent the occurrence of fires, especially thermal runaway caused by external factors such as car accidents, "At present, the world is more optimistic about the so-called 'ultimate solution' or solid-state batteries, which is also the direction of desperate research by automobile powers such as Japan, and they are trying to overtake China's new energy vehicles from the solid-state battery track." ”

Industry insiders call for no choking on food

In Zhang Hong's view, under the current technical conditions, it is necessary to prevent battery safety risks from multiple perspectives.

From the perspective of enterprises, he mentioned that in terms of hardware, under the guidance of relevant national standards, battery manufacturers and OEMs should be more clear about the goal of power battery safety, and ensure that the battery can remain stable in various extreme situations in the design stage, and no dangerous situations such as thermal runaway occur; From the software aspect, the battery management system BMS should be used to ensure the safety of the power battery. In addition, it is 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 without safety issues such as thermal runaway.

From the consumer level, Zhang Hong believes that safety awareness should be improved, and the various performance and configuration of the new energy vehicles they buy should be understood, especially the characteristics of emerging intelligent electric vehicle equipment. Take the initiative to develop safe car habits, such as choosing not to be exposed to the sun when parking, and paying attention to intervals when traveling long distances, so as to avoid the hidden danger of spontaneous combustion to the greatest extent.

He said that from the regulatory level, it is necessary to further play the role of national mandatory standards, accelerate the formulation and revision of power battery safety standards, and require all parties in manufacturing, sales and driving to strictly abide by relevant laws and regulations to build a solid bottom line for power battery safety.

Li Ze (pseudonym), an industry insider, also said that under the current technical conditions, preventing and reducing the risk of thermal runaway of new energy vehicles must be made by the joint efforts of many parties. In particular, he pointed out that "enterprises have an unshirkable responsibility, not only car companies, but also battery companies." Good quality is the first, publicity, consumer education, should be more cautious, rather than confusing the concept, just want to calm people when something happens. ”

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 enterprises is insufficient, each has its own database, and the enterprises are not open on the grounds of "trade secrets", which is not conducive to the all-round management of batteries.

However, Li Ze also said that technology and supervision are gradually advancing, and there are currently relevant regulations such as the "Thermal Diffusion Member Protection Test Specification for Electric Vehicle Power Battery System" and "Safety Requirements and Test Methods for Electric Vehicle Power Battery".

Zhang Hong has also emphasized many times that we must not be discarded by choking on new energy vehicles, and we must be full of confidence in their sustainable and stable development.