No fire, no explosion! Decoding the safety standards and technology trends of power batteries-EEWORLD

Collect

In the new energy vehicle market in 2024, although fire accidents have been greatly reduced compared with before thanks to the advancement of power battery safety technology, they still occur from time to time.

There are many reasons that lead to power battery fires, such as battery design defects, battery management system failures, external physical damage, improper use and maintenance, environmental factors, and so on.

The good news is that the whole society is committed to solving the safety issues of power batteries, both from the policy side and the business side.

Evolution of power battery safety standards

Power battery safety standards play a protective role in the development of new energy vehicles.

In 2020, my country issued the first three mandatory national standards for new energy vehicles, including GB 38031-2020 "Safety Requirements for Power Batteries for Electric Vehicles", GB 18384-2020 "Safety Requirements for Electric Vehicles", and GB 38032-2020 "Safety Requirements for Electric Buses".

Among them, GB 38031-2020 "Safety Requirements for Power Batteries for Electric Vehicles" specifically stipulates the safety requirements and test methods for power batteries (including cells, battery packs or systems) for electric vehicles. The battery cell puncture test is deleted and only used as a trigger condition for thermal runaway of the cell. A battery system thermal diffusion test is added, requiring that after a thermal runaway of the battery cell occurs, the battery system will not catch fire or explode within 5 minutes, leaving safe escape time for the occupants.

Figure 1. (GB38031-2020) Safety test items, methods, requirements (part)

The standard was implemented on January 1, 2021, marking a shift in the understanding of vehicle safety from single-unit safety to system safety. In other words, whether the single-unit puncture passes is no longer important. The key lies in whether the spread of the single-unit thermal runaway can be controlled in time. The concepts of single-unit thermal runaway and system thermal diffusion are distinguished.

On May 27, 2024, in order to further improve the safety of power batteries, the Ministry of Industry and Information Technology issued GB 38031 "Safety Requirements for Power Batteries for Electric Vehicles (Draft for Comments)".

The Draft for Comments further tightens the requirements for thermal diffusion testing of power batteries on the basis of existing standards, mainly including improving thermal diffusion requirements, adding thermal event warning requirements, and improving thermal diffusion testing methods. The Draft for Comments emphasizes the protection capability of the power battery system in the case of thermal runaway of battery cells, and raises the thermal diffusion requirements from "alarm 5 minutes before fire or explosion" to "no fire or explosion". In addition, internal heating trigger is added as one of the recommended methods for thermal runaway triggers.

Figure 2. The thermal diffusion test determination process in the Draft for Comments

According to industry standards, thermal runaway refers to the phenomenon that the battery temperature rises uncontrollably due to the chain reaction of heat release from battery cells. Thermal diffusion refers to the phenomenon that the thermal runaway of one battery cell in a battery pack or system triggers the thermal runaway of the remaining battery cells one after another.

The trend of thermal safety technology of power batteries from BYD's technical solutions

As a company that integrates the production, manufacturing and sales of power batteries and new energy vehicles, and ranks first in the world in new energy vehicle sales, BYD's technical solutions for power batteries have set a benchmark for the industry and are worthy of in-depth analysis and study.

A milestone event was the launch of BYD's blade battery and the release of its battery puncture test in early 2020. From the results of the single-cell puncture test, the ternary lithium battery burned violently, with a surface temperature exceeding 500°C; while BYD's lithium iron phosphate blade battery had no open flame or smoke, and a surface temperature of only 30°C-60°C. It is said that the core purpose of BYD's blade battery puncture test is to cause a short circuit in the battery in order to observe the thermal runaway of the battery and formulate a better safety protection strategy.

Afterwards, according to BYD's public thermal diffusion test data, the battery in the middle was forced to thermally run away, with the highest temperature being about 350°C. At this time, the temperature of the battery in the adjacent position was only 80°C, and the blade battery only emitted smoke, without catching fire or exploding.

It can be seen that based on the lithium iron phosphate material system (low heat generation) and the long and thin blade battery design (fast heat dissipation), the blade battery already has a good ability to control heat diffusion when it was first released.

Figure 3. BYD released a needle test comparison

Blade batteries use lithium iron phosphate materials, which theoretically have relatively weak low-temperature performance. In order to improve the low-temperature performance of blade batteries, many improvements were made in the thermal management system. For example, insulation materials were added to the structural design of blade batteries, and a layer of insulation cotton was placed on the outside of the thermal management system, forming a complete thermal management system for blade batteries. At the same time, the first intelligent dual-circulation battery direct cooling and direct heating technology was created to improve the performance of blade batteries in winter.

Figure 4. BYD Blade Battery Thermal Management Solution

In addition to the design of the battery thermal management system, in February 2023, BYD focused on the patent layout of super heat-absorbing materials between battery cells, such as "Cooling component and battery pack and vehicle with it" (application date: 2023.02.28), "Heat-absorbing component, battery module, battery pack and vehicle" (application date: 2023.02.28), "Package, phase change components arranged between battery cells" (application date: 2023.02.27), "A protective structure and processing method for a battery pack cooling component, battery pack" (application date: 2023.03.28) and other patents, introducing high heat-absorbing materials and phase change components into the battery system, suppressing heat diffusion through a combination of heat absorption + insulation, further reducing the risk of heat diffusion in the power battery pack, and improving the safety and reliability of the power battery pack.

According to patent information, the leaky phase change filling material is mainly a lyophilic polymer material and a liquid phase change medium. The cooling component composed of the skeleton has the characteristics of not being easy to deform, high heat dissipation efficiency, fast heat dissipation response and good exhaust effect.

Figure 5. Related patent drawings

The key point of this technology is to use high heat absorption materials and utilize the latent heat of vaporization of the material to greatly enhance the heat absorption capacity between battery cells. It can completely absorb all the heat transferred from one battery cell to the next due to thermal runaway, thereby making it possible to solve the heat diffusion problem caused by thermal runaway of multiple batteries and the destruction of multiple batteries under extreme working conditions. The technical solution can cover all battery cell sizes and different battery cell systems.

Figure 6. Phase change material filled between battery cells (patent screenshot)

Figure 7. BYD's blade battery

BYD's blade battery "came out of its sheath to protect the world" in 2020 and became famous for passing the needle puncture test. Over the past four years, BYD has continued to use innovative thermal safety technologies, especially the application of high heat absorption materials between battery cells in blade batteries, so that the thermal safety capability of the blade battery system is sufficient to meet the "no fire, no explosion" requirement of the draft for comments.

Veken Lithium Battery noticed that on September 13, BYD obtained an important invention patent, the patent name is "Battery System and Electric Vehicle", the application number is CN201711332873.2. The authorization of this patent marks that the company has taken another solid step in the field of battery technology.

Summarize

According to statistics, as of mid-September, BYD has achieved remarkable results in patent authorization this year, having obtained 2,607 new patent authorizations, an increase of 25.4% over the same period last year.

The continuous rapid development of technological strength is supported by R&D investment. BYD's 2024 interim financial report shows that during the period, BYD's R&D investment reached 19.621 billion yuan, a year-on-year increase of 41.82%, making it the company with the highest R&D investment among A-share listed companies in the first half of the year. This further proves BYD's high attention to R&D and innovation.

Under the "protection" of innovative technologies, BYD's power batteries and new energy vehicles will be safer and more competitive!

Reference address：No fire, no explosion! Decoding the safety standards and technology trends of power batteries

Previous article：Volvo Trucks launches next-generation safety system to protect pedestrians and cyclists
Next article：Intelligence and safety go hand in hand: Interpretation of popular automotive technologies

Popular Resources
Popular amplifiers

Latest Automotive Electronics Articles

Breaking through the intelligent competition, Changan Automobile opens the "God's perspective"
"Gigabit computing power", "Ultra-large screen cockpit" As the competition trend in the automotive industry moves towards intelligence, a new "indicator competition" is unfolding. For users, it is not easy to measure which car is more worth buying. ...
The world's first fully digital chassis, looking forward to the debut of the U7 PHEV and EV versions
On November 15, the 22nd Guangzhou International Automobile Exhibition opened grandly. In the BYD Pavilion in Hall 21, the million-level high-end new energy vehicle brand Yangwang appeared at booth 1B05 with its full product matrix. ...
Design of automotive LIN communication simulator based on Renesas MCU
1. Introduction to project functions This project is designed to assist automotive communication and electronics industry personnel in debugging LIN communication logic and testing products. In the automotive electronics communication industry, the functional modules used in LIN communication may include ...
When will solid-state batteries become popular?
Solid-state batteries are seen as the future technology of the electric vehicle industry. Major companies have announced plans for mass production. Among the industry giants, a newly established startup, Tailan New Energy, has emerged as a leader in the electric vehicle industry with its innovative " ...
Adding solid-state batteries, CATL wants to continue to be the "King of Ning"
If the attitudes of major automakers and battery manufacturers towards solid-state batteries were still somewhat cautious and reserved in 2023, by 2024, everyone's attitude had reversed 180 degrees, and solid-state batteries became the new ...
The agency predicts that my country's public electric vehicle charging piles will reach 3.6 million this year, accounting for nearly 70% of the world
U.S. senators urge NHTSA to issue new vehicle safety rules
Giants step up investment, accelerating the application of solid-state batteries
Guangzhou Auto Show: End-to-end competition accelerates, autonomous driving fully impacts luxury...

MoreSelected Circuit Diagrams

Change More Related Popular Components

MorePopular Articles

MoreDaily News

Guess you like