How is the safety performance of the power battery?

As the "heart" of electric vehicles, the progress of power batteries has made today's electric vehicles, and it also determines the pace of marketization of electric vehicles in the future. In 2018, the power battery industry entered the fast lane of development. With the continuous maturity of new battery technologies, the safety of power batteries has gradually become the focus of attention.

In May, a Tesla ModelS in Florida, USA, hit a concrete wall and quickly caught fire, killing two high school students and injuring another high school student. In the same month, an accident occurred in a Swiss Tesla car in Switzerland, causing the battery to catch fire and the driver to die on the spot... The continuous accident once again pushed the safety of the electric vehicle battery to the cusp of the wind, and also raised doubts for consumers who are willing to purchase electric vehicles. : Electric car, is it safe?

Power battery safety to be tested

The news of the explosion of well-known brand mobile phone batteries has been going on for a long time, but it still leaves many people with a lingering fear. The recent electric car fire accident is even more shocking. Under the blessing of energy saving, environmental protection, and high cost performance, can electric cars let everyone sit on a large battery with peace of mind?

"The overall technical level of domestic power battery production is still far from the advanced level of foreign countries." Wang Zhan, an engineer at China Quality Certification Center, said that in recent years, the number of domestic power batteries has grown rapidly, new technologies and new routes have emerged in an endless stream, but manufacturers are generally not large. Big, technical strength has room for improvement. Under the current system, the market threshold is relatively low, and some small manufacturers have not yet established a standardized quality assurance system. “Most companies use a combination of semi-automated and automated production equipment in the production process, the quality of the product is unstable, and there is room for improvement in terms of capacity and safety.”

According to the reporter, lithium iron phosphate and ternary lithium batteries are currently the most used power batteries on the market. The data shows that the lithium iron phosphate battery has lower energy density than the ternary lithium battery, but it has better safety than the ternary lithium battery. The positive electrode material is the key factor determining the energy density and performance of the battery. The separator is the key material to ensure the performance and safety of the battery. It is well known that the greater the battery capacity and the higher the energy density, the more important the importance of safety.

Ouyangminggao, an academician of the Chinese Academy of Sciences and a professor at Tsinghua University, stressed that in the development of electric vehicle power batteries, safety is always the first, and other performance indicators such as energy are second.

"It is not only the battery itself, but also the battery pack, the power system, the whole vehicle, etc., especially the BMS (Battery Management System)." Ye Jiping, a professor at Tongji University, said that the current BMS cannot be like a human nerve. To achieve "cool and warm self-knowledge", all batteries are passively controlled by BMS, and the internal activity of the battery is very large, and it is impossible to see the internal operation under the exposure of the atmosphere, although the material analysis technology is very mature in Japan, Korea and other places. But domestic research has only just begun. So people's concerns are not unreasonable.

The battery is safer than you think

Experts in the industry believe that Tesla's fire is caused by the "thermal runaway" phenomenon caused by the ternary lithium battery in the face of a strong collision, resulting in a rapid rise in temperature.

The same is the car, why do you sit on the gasoline car every day, everyone is not so worried; and in the electric car, people are very concerned about safety?

Because the factors affect "electricity" are more than gasoline. “There are five failure modes of the battery system: electric shock (non-normal power release), combustion, explosion, collision, corrosion.” Zhang Renbai, vice president of Beijing Price New energy battery Technology Co., Ltd. introduced that there are at least four battery system safety tests. Great safety, the first is chemical safety, including material flame retardant, battery safety; the second is electrical safety, including expansion force, sensing, voltage acquisition, temperature acquisition, etc.; the third is mechanical safety, such as corrosion resistance, vibration resistance The fourth is functional safety, such as automatically cutting off the circuit to extinguish the fire during the collision.

“Whether it is overcharge or short circuit, most of the problems are caused by the thermal runaway of the battery. In the future development, we still have to continue to work on stable positive and negative materials.” Chairman of Fueng Technology (Zhangzhou) Co., Ltd. Wang Wei said that the current common safety measures include fusible fuses, relays, cabinets, batteries, battery modules, liquid cooling systems, thermal management and so on.

Wang Fang, chief expert of China Automotive Technology and Research Center, also stressed that safety is the foundation of electric vehicles. "Electric car safety is personnel safety, requiring no fire or explosion before people escape." But she also said that the safety of the battery is graded. "Security is relative, and insecurity is absolute. We just want to bring the possibility of insecurity to zero infinitely."

In addition to technical improvements and rigorous testing, the China National Quality Supervision, Inspection and Quarantine Bureau and the China National Standardization Administration jointly issued the Lithium Ion power battery Pack and System for Electric Vehicles on May 15, 2015. Part 3: Safety requirements and test methods (GB/T31467.3-2015) and other six national standards, and fully implemented in 2016. On January 24, 2018, the Ministry of Industry and Information Technology issued the "Notice on Soliciting <; Safety Requirements for Electric Vehicles>; and 3 Mandatory National Standards (Draft for Comment). A series of national standards will uniformly enforce battery safety and set a clear “safety bottom line”. Some industry commentators have indicated that the interconnection and combination of different standards covers various grades of power batteries, modules and systems, which is conducive to the healthy development of the power battery industry.

Battery companies and car companies join forces to create a sense of security

Industry experts generally said that the safety of new energy vehicles is not a problem of a certain link, a certain enterprise, but a system engineering including a battery, motor, electric control, vehicle manufacturing, charging facilities and other full chain. Ensuring battery safety is not just the “business” of battery companies, but the whole vehicle company is even more responsible.

In terms of battery companies, “need to ensure the safety of power batteries and energy storage batteries from design to production, from use to after-sales.” Huang Shilin, vice chairman of Ningde Times New Energy Technology Co., Ltd. suggested.

If battery companies focus on the development of battery performance, then vehicle companies are more concerned about battery use and user experience. Representatives of car companies and battery companies said that although the two sides seem to have a "clear division of labor", in fact, buying and selling does not necessarily require "two clear." The vehicle enterprise collects data during the user's use, reflects the user experience and problems, and the battery enterprise as a reference can better improve the performance and safety of the battery. Zhang Hailiang, chairman of Zhejiang Dianjia Automobile Technology Co., Ltd., suggested that vehicle manufacturers need to abandon the traditional supply and demand relationship between OEMs and suppliers, and work closely with suppliers to promote the iterative and evolution of battery technology. .

Zhang Xiyong, general manager of Beijing Automotive Group Co., Ltd. said that the development of power battery technology directly affects the fluctuations and control capabilities of vehicle manufacturers. The relationship between vehicle and parts is interdependent and common progress, and must be based on industrial development, the height, adherence to the open, cooperative mentality jointly meet the challenges, and embark on a new path to adapt to the new ecology of the new energy vehicle industry.

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