Talking about Battery Safety of Electric Vehicle

The country's new-energy vehicles are growing rapidly, but the recent sudden shift in the direction of its "heart" power battery policy has brought huge uncertainty to the development of the industry.

According to statistics, sales of new energy vehicles exceeded 300,000 last year. A pure electric car costs nearly half of the vehicle's battery cost. At present, the pure electric vehicle battery technology route is roughly divided into three batteries and lithium iron phosphate batteries.

On January 14, the Ministry of Industry and Information Technology released the "Catalogue of Recommended Vehicles for the Promotion and Application of New Energy Vehicles." Among them, there is no three-way electric commercial passenger car, which means that models that do not enter the catalogue will not enjoy government subsidies and purchase tax exemption. (10 <UNK>) policy benefits. In response, Liuyanlong, Secretary General of the China Chemical and Physical Power Industry Association, said that the output and installed capacity of three-part material power lithium batteries have been greatly affected. Once the risk assessment is completed and the corresponding safety standards and measures are in place, the industry will welcome new development opportunities.

Electric vehicles and battery manufacturers affected

In general, ternary materials have advantages in battery energy density, high-magnification charging, and low temperature performance, while lithium iron phosphate materials have long life and high safety. In December, an electric bus in Hong Kong fired with a three-way power battery.

Subsequently, at the January 24th meeting of 100 electric vehicles in China, Zhangxiangmu, Director of the Equipment Industry Department of the Ministry of Industry and Information Technology, said that the Ministry of Industry and Technology is organizing a risk assessment under the current safety standard system of three lithium battery passenger cars. "Before the evaluation is completed, Suspension of Ternary lithium battery passenger cars included in the list of recommended models for the promotion and application of new energy vehicles. "

On the Development of High Energy Density System in Electric Vehicle Battery Safety

Liuyanlong said that at present, the new energy car industry has been developed by state policy subsidies, and the state has suspended subsidies for three-yuan power battery buses, which has a great impact on the enthusiasm of depots.

In an interview with a reporter from the China Science and Technology Daily, Dr. Kirk, vice president of the Chaowei Group Research Institute of China's leading battery industry and national expert on the "Thousand People Plan", said that Chaowei adheres to multiple technical routes and multiple specifications in the power lithium-ion battery technology line. Product parallel. Among the power battery products that are put into the market in bulk, there are both lithium iron phosphate battery systems and ternary material systems. "But before the suspension of the Ternary lithium battery passenger car was included in the catalogue of new energy vehicle promotion and application models, Chaowei received orders for Ternary materials. Therefore, the enterprise production plan will be affected. "

Battery safety battle

Does the Ministry of Industry and Information Technology temporarily stop lithium ternary batteries, while other types of power cells such as lithium iron phosphate are not affected, which means that batteries such as lithium iron phosphate are safer than ternary material systems?

Kirk thinks this is not the case. He said the safety of new-energy vehicles and lithium-ion battery systems depends on a variety of factors, including the lithium-ion battery cathode material system, rather than the cathode material itself.

Also at a meeting of 100 Chinese electric cars, Ouyangming, a professor of automotive engineering at Tsinghua University, reported the results of safety accidents in new energy vehicles in China. The results show that the accident mainly comes from the short-circuit caused by the collision, the short-circuit caused by the intake of the battery, the failure of the electric connection, the overcharging of the battery, and the short-circuit caused by the leakage of the core.

"The accidents such as the fire when the Shenzhen Wuzhoulong vehicle was charged and the Xiamen bus fire were exactly lithium iron phosphate batteries. This shows that the safety of the monolithic material does not represent the safety of the power battery system or the entire vehicle. "Kirk said that the safety of power battery systems and new energy vehicles is a systemic issue. BMS (management system) strategy, vehicle control strategy, battery charge and discharge management, battery layout design and system manufacturing will all affect vehicle safety, and the monomer positive electrode material is only one of the factors.

Simply from the mechanism of combustion or explosion in the event of an accident in a lithium ion battery, it is a so-called "thermal runaway" process. Kirk explained that the first is due to various factors that cause the internal temperature of the battery to rise. As the temperature rises, a series of processes will further lead to the generation of heat. These processes can not be discharged in time, causing the battery temperature to increase further. To reach the positive pole and electrolyte decomposition temperature, With the complete collapse of the diaphragm and even the ceramic coating diaphragm, the temperature rises sharply, and the final battery is violently burned or exploded.

The decomposition temperature of lithium iron phosphate is higher than that of the ternary material, and the decomposition of the ternary material to produce oxygen promotes the subsequent thermal runaway. From this point of view, lithium iron phosphate is relatively safe. However, Kirk believes that from the point of view of the thermal runaway process, the thermal stability of a simple positive material is not a decisive factor in the safety of lithium ion batteries. The actual accident case of the complete combustion of a lithium iron phosphate battery passenger car also proves this.

Developing High Energy Density power battery System is the Mainstream Trend

According to statistics, ternary batteries currently account for more than 80 in the global lithium ion battery market.

Kirk said that the development of high-energy density power cell system is the international mainstream trend. High energy density is one of the core technical indicators of China's "13th Five-Year Plan" power cell, which is also the current industrial range of electric vehicles. Still not meeting the inevitable result driven by market demand. The current high energy density system of international industrialization is dominated by three yuan.

"Samsung and other companies are not special cases of focusing on the development of ternary batteries. They are following the international trend. The advantages and disadvantages of the technology line itself should be judged more scientifically by the market itself. " said Kirk.

At the two sessions this year, Zhangtianren, deputy to the National People's Congress and chairman of Tianneng Group, also said that China's high-end lithium battery industry should not be satisfied with state subsidies alone, but should rely on technological innovation and brand building, especially in the Ternary system. In the future, it can compete with Samsung and Panasonic.

The page contains the contents of the machine translation.