Ouyang Minggao, a professor of automotive engineering at Tsinghua University, reported the statistical results of China's new energy vehicle safety accidents. The results show that the accident mainly comes from the collision caused by a short circuit, the battery outside the water short circuit, the electrical connection failure, battery overcharge, battery leakage caused by external short circuit and other factors.
New energy vehicles in China are rapidly developing, but the recent sudden changes in the direction of the "heart" power battery policy have brought great uncertainty to the development of the industry.
According to statistics, last year, China's new energy vehicle sales exceeded 300,000. A pure electric car, battery costs account for nearly half the cost of the vehicle. At present, pure electric vehicle battery technology roughly divided into ternary battery, lithium iron phosphate battery two.
January 14 this year, the Ministry of Industry released "new energy vehicles to promote the use of recommended models directory," which did not see ternary electric commercial buses, which means that did not enter the "directory" models will not be able to enjoy government subsidies, and avoid the purchase tax 10%) policy preferences. In response, China Chemical (601117, stock it) and the Secretary-General Liu Yanlong Physical Power Industry Association, said the ternary material power lithium battery production and installed capacity greatly affected. Once the risk assessment is completed and the corresponding safety standards and measures introduced, the industry will usher in new opportunities for development.
Electric vehicle and battery manufacturers are affected
Overall, ternary materials have advantages in terms of battery energy density, high rate charging, low temperature performance and the like, whereas lithium iron phosphate materials have long life and high safety. In December last year, an electric bus fire explosion involving a ternary material powered battery occurred in Hong Kong.
Subsequently, on January 24 this year, China's electric car hundred people's meeting, Ministry of Industry and Information Technology Equipment Industry Minister Zhang Xiang Mu said that the Ministry of Industry is organizing the implementation of the Sanyuan lithium battery buses and other models under the current safety standards system risk assessment, "the assessment is completed Before the suspension of triple lithium battery buses included in the application of recommended models of new energy vehicles directory. "
Liu Yanlong said that at this stage of the new energy automotive industry is subsidized by the national policy to be developed, the state suspended the subsidy for the ternary battery, which has a great impact on the enthusiasm of the depot.
China's battery industry, "leading" enterprise Chaowei Group Vice President, National "thousands of people plan" Dr. Kirk in an interview with Science and Technology Daily reporter said that Chaowei lithium-ion battery technology in the power line, adhere to a number of technologies Route and a variety of products in parallel, the bulk of the battery into the market, both lithium iron phosphate battery system, but also includes ternary material system. "However, before suspending the three-way lithium battery buses into the list of new energy vehicles to promote the application of models, Chaowei received orders also have ternary materials. Therefore, the production plan will be affected."
Battery security dispute
Ministry of Industry temporarily halted ternary lithium batteries, lithium iron phosphate and other types of power batteries are not affected, does this mean lithium iron phosphate batteries and other ternary materials than safer system?
Kirk does not think so. He said the safety of new energy vehicles and the safety of lithium-ion battery systems depend on many factors, including the lithium-ion battery cathode material system, not just the cathode material itself.
Also at the 100th China Electric Vehicle Conference, Ouyang Minggao, a professor of Automotive Engineering at Tsinghua University, reported the statistical results of China's new energy vehicle safety accidents. The results show that the accident mainly comes from the collision caused by a short circuit, the battery outside the water short circuit, the electrical connection failure, battery overcharge, battery leakage caused by external short circuit and other factors.
"Shenzhen Continental Chau dragon vehicle charging fire, Xiamen bus fire and other accidents are just lithium iron phosphate battery, indicating monomer material safety and does not represent the safety of the battery system or vehicle." Kirk said the battery system , The safety of new energy vehicles is a systemic problem. BMS (management system) strategy, vehicle control strategy, battery charge and discharge management, battery layout design and system manufacturing will affect the vehicle safety, and the single cathode material is only one of the factors.
Pure lithium-ion battery accident occurred from the combustion or explosion mechanism, is a so-called "thermal runaway" process. Kirk explained that the first is due to a variety of factors caused by internal battery temperature rise, as the temperature rises, there will be a series of further lead to heat generation process, these processes can not be discharged in time to heat, causing the battery temperature further increased to reach Cathode and electrolyte decomposition temperature, and with the diaphragm even a ceramic coating separator collapse, the temperature rose sharply, eventually the battery intense combustion or explosion.
Lithium iron phosphate decomposition temperature is higher than the ternary materials, ternary material decomposition of oxygen to promote thermal runaway thereafter, from this perspective, lithium iron phosphate is relatively safe. But Kirk believes that from the thermal runaway process, pure thermal stability of the cathode material is not a decisive factor in the safety of lithium-ion batteries, lithium iron phosphate battery bus combustion case of the actual accident also proved this point.
The development of high energy density battery system is the mainstream trend
According to statistics, ternary battery currently accounts for more than 80% of the global lithium-ion battery market.
Kirk said that the development of high energy density battery system is the mainstream of the international trend, high energy density is China's "13th Five-Year Plan" one of the core power battery technology, which is the current industrialization of electric vehicle mileage, has not yet met The inevitable result of market demand. At present, the high energy density system of international industrialization mainly consists of ternary elements.
"Samsung and other companies focus on the development of ternary battery is not a special case, is followed by the general trend of the international technology route itself, the merits of the market itself should be judged more scientific." Kirk said.
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