In the process of its rapid development, new energy vehicles have always been accompanied by safety problems. The frequent occurrence of fire and other accidents has always been the concern of the public.
Shenzhen new energy vehicle application and Promotion Center issued the emergency notice on strengthening the operation safety of new energy pure electric trucks, which mentioned that due to many battery thermal runaway accidents during charging and operation of new energy pure electric trucks in Shenzhen.
In order to ensure the safety of people’s lives and property and prevent and reduce such accidents, vehicle operation enterprises and vehicle production enterprises are required to carry out investigation on the causes of accidents as soon as possible, relevant enterprises and individuals are required to stop the driving of vehicles immediately, and various charging facility operation enterprises are required to increase the monitoring of vehicle charging safety.
On the second day after Shenzhen new energy vehicle application and Promotion Center issued the emergency notice, the Quality Development Bureau of the State Administration of Market Supervision issued the notice on Further Strengthening the recall management of new energy vehicle products.
Among them, with regard to the frequent safety problems of new energy vehicles, relevant departments and enterprises are required to immediately organize investigation and analysis when they are informed of traffic collisions, fires and other related accidents of new energy vehicles produced, sold or imported in the Chinese market, and report the investigation and analysis results to the quality Development Bureau of the State Administration of market supervision.
In recent years, the state and several local governments have issued relevant policies to support the accelerated promotion of pure electric vehicles in the field of logistics and express delivery. Pure electric logistics vehicles have gradually replaced fuel vehicles as the mainstream environmental protection vehicles in the logistics and express delivery industry. With the strong support of the government, the role of pure electric logistics vehicles in cities has become prominent, showing explosive development, but safety problems In particular, the disadvantages exposed by battery safety problems are also increasing.
In 2018, there were dozens of safety accidents caused by explosion of pure electric logistics vehicles in China. For example, in July 2018, the pure electric logistics vehicle dedicated to Beijing vegetable basket Distribution Co., Ltd. caught fire during charging, and the relevant person in charge of the company disclosed that several electric faults had occurred in the previous use, resulting in the vehicle unable to be used normally.
In August 2018, an electric truck in Liaocheng, Shandong Province caught fire due to spontaneous combustion; In the same month, an Ankai electric bus in Tongling, Anhui Province caught fire; In the same August, there were many spontaneous combustion accidents of pure electric mini vans in Shenzhen.
A top management of a well-known domestic pure electric animal flow vehicle enterprise once disclosed that the obvious increase in fire accidents of pure electric flow vehicles in 2018 was mainly related to the high-energy density battery system widely used in vehicle models.
Previously, in the subsidy policy for new energy vehicles, the energy density of the battery system loaded by vehicles has become one of the important indicators; It is clearly required in the subsidy policy that the energy density of power battery system loaded on special vehicles such as pure electric trucks shall not be less than 115wh / kg. For pure electric passenger vehicles, the subsidy shall be doubled for vehicles with battery system energy density of 120 (inclusive) – 140wh / kg, 1.1 times for vehicles with battery system energy density of 140 (inclusive) – 160wh / kg, and 1.2 times for vehicles with battery system energy density of 160wh / kg and above.
Driven by the subsidy policy, car enterprises are more inclined to adopt high-energy density power battery system; At the same time, in order to meet the needs of the terminal market, pure electric logistics vehicle enterprises are increasing high endurance capacity and realizing rapid charging.
however, Insiders said: “From a technical point of view, the relationship between high energy density and high fast charging rate of battery is similar to a seesaw. Under the premise of ensuring high energy density, it is generally difficult to achieve the fast charging requirements of high rate, especially the stability of ternary battery is relatively poor. Therefore, under high-power fast charging, the battery system with poor product performance and technology is prone to thermal runaway and fire Accident. “
Most pure electric logistics vehicles in the market use ternary batteries, the energy density is relatively controllable, and the battery charging rate is 0.5c or less; However, in order to realize fast charging, almost all pure electric logistics vehicles are equipped with fast charging function, and the charging rate is above 1C.
In this case, the high energy density of the battery system is also greatly improved. At present, the ternary material battery can not well solve the problem that it is difficult to reconcile the high energy density and fast charging rate, which leads to the increased risk of spontaneous combustion of vehicles.
In addition, pure electric logistics vehicles have strict cost control. The performance of three electric products is lower than that of passenger cars. The battery enterprises supporting pure electric logistics vehicles on the market are mixed. The application of ternary batteries in pure electric logistics vehicles has only been two years since 2016.
On the one hand, the technical level of battery enterprises is limited, on the other hand, they can not guarantee the battery safety, and improve the high energy density and fast charging high rate, which leads to the battery safety of pure electric logistics vehicles can not be guaranteed. Further, the safety of pure electric logistics vehicles is also worrying.
Yang Yusheng, academician of the Chinese Academy of engineering, once pointed out that due to the one-sided pursuit of high driving range of pure electric logistics vehicles, the wind of high nickel of ternary materials is getting stronger and stronger, but ternary batteries may actually be a time bomb with low safety. At the same time, although the high nickel of batteries improves the specific capacity, increasing the nickel content in ternary batteries also makes the thermal runaway temperature and safety of batteries gradually decline, It will inevitably bring greater potential safety hazards; Therefore, the industry suggests that lithium iron phosphate batteries should not be buried.
