Electric vehicles can not be "sick on duty"

Recently, Samsung smart phone Galaxy Note 7 due to the explosion of lithium battery recall caused widespread consumer concern. Small cell phones will explode, often carrying hundreds of kilograms of power lithium battery electric vehicles are still safe?

There's no future for electric cars without safety.

By the end of 2015, the accident rate of electric vehicles in China was 0.17 %. "Safety is a prerequisite for the development of electric cars. There is no future for electric cars without safety. China has had 31 electric car accidents since 2011, including nine in 2015 and eight in the first half of the year, Li Dong, director of the equipment industry Department of the Ministry of Industry and Information Technology, said at a recent Summer Forum of 100 Electric Vehicles in China.

Another statistical data shows that as of the end of 2015, China's electric vehicle accident rate reached 0.17%, more than double the world average. “The number of electric vehicle accidents is growing, one reason is the rapid growth of sales.” Li Dong said that since the “12th Five-Year Plan”, China has sold 440,000 new energy vehicles, and sold only 330,000 vehicles in 2015. Among them, more than 70% of pure electric vehicles. With the aging of vehicles, batteries and wiring harnesses, the safety risks of electric vehicles are increasing further.

"The more typical accidents of electric vehicles are spontaneous combustion, collision and fire, and overcharging. For example, Zhourong, chief engineer of the China Automotive Technology Research Center's Standards Institute, said that on April 26, 2015, Wuzhoulong A10 pure electric bus spontaneously ignited when charging at the Shenzhen Bay Plus Power Station of Putian New Energy in Shenzhen, causing serious damage to the vehicle. Fortunately, no casualties occurred. The investigation showed that this was a typical overcharge fire accident. "At the time, the vehicle battery management system crashed, but the charging machine did not take emergency measures accordingly, but continued to charge. As a result, the battery was overcharged for 1 hour and 18 minutes, and the overcharged was 57.9 kilowatt-hours. In the end, the battery could not withstand, ruptured and burned. "

Concerned about power lithium battery safety electric vehicle can not "bring disease to work"

Another well-known plug-in hybrid passenger car spontaneous combustion accident is also due to charging. "The Shanghai car owner did not install a charging post. When charging with a flying wire, the terminal block was mistakenly placed on the back seat of the vehicle." An industry expert said that fortunately, only the vehicle was burned and no casualties were caused.

"Whatever caused the accident, the main sign of an electric car safety accident is that the battery heat is out of control. "The first is that the single core heat is out of control, and the heat generated during this period can increase the temperature of the battery by 400-1000 degrees Celsius," said Ouyang Minggao, executive vice chairman of the China Electric Vehicle 100. Then the heat out of control will spread like firecrackers in the battery module, and the vehicle will smoke, catch fire, and even explode. The degree of damage caused by thermal runaway and the speed of chain reaction are closely related to the thermal stability of battery materials. Among the various types of power batteries, the lowest temperature of heat runaway of lithium iron phosphate batteries is higher than that of other materials.

Li Ping, chairman of the New Energy Technology Co., Ltd.(CATL) in the era of Ningde, explained that the image is even more vivid -- from the material characteristics, lithium iron phosphate batteries burn like "coal", while the three-element lithium batteries burn like "gunpowder." Li Ping said that the high activity of ternary materials and the energy density(the electrical energy released by the average unit volume or mass of the battery) can theoretically reach 300 Wh / kg, but the thermal stability is poor, at an external temperature of about 200 °C. It breaks down and releases oxygen, which, along with combustible electrolytes and carbon materials in the battery, is at one point and will ignite in a very short period of time. The energy density limit of lithium iron phosphate is 150 Wh / kg, but the stability is higher. Decomposition occurs at 700 °C and oxygen is not released. Even in extreme cases, the combustion of lithium iron phosphate is not intense, the fire expands slowly, and the fire is easier to extinguish.

Huanghao, deputy researcher at the Shanghai fire research institute of the ministry of public security, said that since last year, there have been safety accidents in the production of power batteries, such as storage, vehicle operation, and shelving of old cars. Among them, in May, July and August this year, there were three fires in the production and storage of lithium batteries, resulting in the sacrifice of a fire chief and the injury of 10 firefighters during the fire fighting.

Electric car safety can do better

The fuel truck will also spontaneously ignite, and the danger of the power battery can be completely controlled by systematic measures. "As an energy carrier, lithium-ion batteries must have certain dangers, but this danger can be completely controlled by systematic measures. Wang Fang, chief expert in the power cell field at the China Automotive Technology Research Center and secretary general of the Battery Testing and Applied Technology Alliance, believes that traditional car fuel tanks and high-pressure hydrogen storage tanks for fuel cells are also dangerous. There are also a number of conventional car spontaneous combustion and collision and fire accidents that occur every year.

The safety hazard of electric cars should not be entirely blamed on power cells. "Four of the 17 accidents since 2015 were battery system accidents, six were related parts accidents, two were caused by defects in the charging system, and five were caused by illegal modifications or improper use. Mr. Li believes ensuring the safety of electric vehicles involves both the entire industrial chain and the full life cycle of the product. In terms of the entire industrial chain, the cause of the accident involves cell cells, batteries and management systems, wire bundles, high-pressure parts, charging piles, charging stations, etc.. From the perspective of the full life cycle, it involves the manufacturing and storage of batteries and vehicles, transportation and maintenance, scrapping and recycling and dismantling.

"Electric vehicle safety technology covers three parts: power batteries, complete vehicles and charging infrastructure. Mr. Ouyang Minggao believes battery companies must do everything possible to minimize the risks and hazards of runaway heat. At present, the technology of lithium iron phosphate in power battery enterprises in China has become relatively mature, and the safety of three-way positive and graphite negative pole cells has also been greatly improved, and innovations have been made in flame retardant diaphragm, flame retardant electrolysis, and flame retardant safety. The test results of monomer battery products are not very different from those of foreign countries.

To ensure the safety of electric vehicles, vehicle companies are duty-bound. Among them, the scientific safety concept, the rigorous development process, the collision protection performance beyond the same level, and the perfect electronic and electrical safety protection program are all necessary. "BYD’s electric car waterproof performance, Changan electric car collision safety, SAIC Rongwei's complete electric vehicle safety protection program are doing very well." Ouyang Minggao pointed out that compared with the international advanced level, we still have to learn The place. For example, he said that the Nissan pure electric car is listening to the wind, and the global sales have been about 230,000. There has not been a major accident. This is due to the safety concept of stratification and grading of Nissan – the first is to prevent and control accidents; secondly, once thermal runaway occurs, it is necessary to avoid burning and explosion of the whole vehicle; again, if something goes wrong, the accident should be controlled within the controllable range. Inside, the consequences are the same as for a fuel car. To this end, they have adopted a strict V-type development model, from materials, cell cores to battery packs, modules, from the design layer to the verification test layer, all in strict accordance with the above concepts and models.

"A complete test verification system is also essential. Zhu Jun, deputy director of the SAIC Technology Center, told reporters that the battery of the Rongwei 550 plug-in hybrid sedan not only passed tests such as acupuncture, fire, electrochemistry, high pressure, collision, and extreme cold and heat according to national standards. It also passed the professional safety certification of UL Corporation in the United States. Considering that more than a dozen electric vehicles burned down during a typhoon in New York, SAIC's vehicle immersion test took about nine months to immerse the entire battery in seawater, leaving the system intact.

Don't let electric cars get sick

We will improve technical standards and strengthen research and development capabilities. In January this year, due to the safety of power batteries, the Ministry of Industry and Information Technology suspended the inclusion of three lithium battery passenger cars in the list of recommended models for the promotion of new energy vehicles. This means that the relevant vehicle factory can not obtain a financial subsidy of a minimum of 600,000 yuan per vehicle at the central plus local level until the risk assessment of the current safety standard system for the three-way lithium battery passenger car is completed. This move once caused controversy in the industry.

"Looking back, the decision of the Ministry of Industry and Information Technology was very forward-looking. "Zhuguanghai, deputy director of Yutong Technology Center, believes that passenger cars should have higher safety requirements. In new energy buses, in particular, power batteries must be made sure that they have enough time to escape once they catch fire. A bus carrying dozens of passengers would take minutes to evacuate, even if it was orderly, compared with the shortest flight time of about 20 seconds for passenger cars. Because the subsidy standards for new energy passenger cars are too extensive, it not only triggered the "deception" behavior, but also caused many companies to quickly launch products while ignoring the safety of the vehicle, resulting in a small number of electric vehicles with "disease" hidden dangers.

Zhuguanghai said yutong is also working on a set of safety test guidelines for new energy vehicles, in addition to the 15 safety tests for battery packs and battery systems set out in national standards. As of now, there is no ready-made version at home and abroad. This is also an important reason why the Ministry of Industry and Information Technology has stopped the subsidies for Ternary  lithium electric buses.

In fact, the need to improve the standard is far more than Ternary lithium buses. The safety inspection results of new energy vehicles and charging facilities organized by the Ministry of Industry and Information Technology and the Energy Bureau show that some enterprises still have hidden dangers in product design, quality control, after-sales service, etc., and there are still loopholes in the safety monitoring and management systems in some places. Ouyang minggao added that the quality of domestic charging equipment is not particularly good, waterproof, dust-proof, anti-corrosion, leakage of electricity, short-circuit protection and other problems.

It is reported that the Ministry of Industry and Information Technology led the organization of long-range monitoring standards for electric vehicles, safety conditions for electric buses will be released and implemented, battery management system technical conditions, power cell coding and specifications are being revised. At the same time, the Regulations on the Administration of Access to New Energy Vehicle Production Enterprises and Products(Revised Draft for Consultation) have been issued, and it is planned to significantly increase the R&D capabilities and production consistency requirements of new energy vehicle qualification declaration companies.

"The breakthrough and industrialization of electric technology may come faster than people expect. Li Ping said that the energy density of lithium-ion batteries is currently 1.5 times higher than in 2012, and the energy density of power batteries has increased to 300 Wh / kg in 2020 and 350 Wh / kg in 2025. There is no technical problem. The economies of scale brought about by the rapid increase in market capacity will also greatly reduce the cost of power batteries. However, it must be seen that the resulting safety challenges will be greatly enhanced. The safety technology system around high-energy density lithium-ion batteries above 300 W/kg will become the most important core technology for the new generation of high-performance electric vehicles.

The page contains the contents of the machine translation.