News from China Energy Storage Network: "To prevent future electric vehicle fires, we must first eliminate the bad apples in the enterprise. Secondly, the government must be more steady in improving energy density. Finally, the direction of technological improvement is not wrong, but it must be comprehensively measured." On September 17, Ouyang Minggao, academician of the Chinese Academy of Sciences and professor of Tsinghua University, expressed the above views to Autohome at the inauguration ceremony of the new energy vehicle "wind solar gas storage and charging" comprehensive test demonstration platform jointly built by Tsinghua University and Xingxing Charging.

　　Problems exposed behind electric vehicle fires

　　In Ouyang Minggao's view, the frequent fire accidents of new energy vehicles in China this year have exposed many problems, such as poor waterproofing throughout the vehicle's life cycle. For example, on August 31, a white car caught fire near Zengcheng Square in Guangzhou and spontaneously combusted. The reason is the fire accident caused by the owner continuing to use the vehicle after soaking it for 2 hours; secondly, the aging problems of components such as relay adhesion, plug-in aging, and connection aging during vehicle use cannot be ignored; thirdly, the safety design level of the charging function in the charging facilities Low quality, failure of products to strictly implement charging safety standards, etc. are also causes of fire accidents.

　　In addition, Ouyang Minggao pointed out that the technical level of thermal spread suppression of battery systems needs to be improved, because too fast a heat spread will cause the occupants to lose the chance of rescue, and the design of existing models leaves people with too short escape time. For example, the escape time of a car is less than 30 seconds, less than 5 minutes for passenger cars.

　　The main cause of foreign electric vehicle fire accidents is high-speed collisions, with charging taking a back seat. For example, among the four reported foreign Tesla fire accidents, three were caused by collisions. This is slightly different from the cause of fire accidents in China.

　　Vehicle fires have both objective and subjective factors

　　The objective factors are mainly structural problems in the power battery itself. For example, the lithium-ion batteries currently used in new energy vehicles will cause lithium deposition in the battery under conditions such as low temperature, fast charging, and micro overcharging. What are the consequences of lithium precipitation? It will cause lithium dendrites to continue to grow until they pierce the battery separator and cause a short circuit, causing contact between the positive and negative electrodes, rapid accumulation of heat, causing the battery pack to catch fire and threatening the safety of the vehicle and its owners.

　　The subjective factors lie in the fact that companies fail to comply with relevant technical standards or their technical level is not high, as well as Ouyang Minggao mentioned that “there are many black sheep in the new energy industry.” The latest data shows that from January to August, China sold a total of 18.0961 million cars, of which 601,000 new energy vehicles were sold. However, there are more than 200 manufacturers of new energy vehicles, which only account for 3% of the automobile industry. This has resulted in a mixed bag of good and bad new energy products on the market. The market is in urgent need of rectification, and manufacturers also need high-standard restraint and supervision to prevent the "black sheep" in the industry from hindering the development of China's new energy vehicles.

　　Finally, Ouyang Minggao pointed out the measures to improve the safety of existing power batteries, such as the oxygen release of the positive electrode of high-nickel ternary lithium-ion power batteries, which can delay the oxygen release of the positive electrode through interface modification and improve the thermal stability of the electrode; for electrolyte combustion If the problem occurs, solid electrolyte can be used instead of organic electrolyte, thereby completely solving the intrinsic safety problem of electrolyte combustion. (Text/Car Home Song Aiju)

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