The safety of electric vehicles is the focus of consumers' attention, and it is also the fundamental guarantee for the sustainable and healthy development of the new energy automobile industry. The three mandatory standards further improve and optimize the safety technical requirements of electric vehicles and power battery products.
Among them, the "Safety Requirements for Electric Vehicles" mainly stipulates the electrical safety and functional safety requirements of electric vehicles, and increases the requirements for thermal event alarm signals of battery systems, which can remind drivers and passengers to pay attention to safety at the first time; Strengthen the waterproof, insulation resistance and monitoring requirements of the whole vehicle, and reduce the safety risks of normal use and wading of vehicles. Optimize the test methods such as insulation resistance and capacitive coupling to improve the test accuracy and ensure the high voltage safety of the whole vehicle.
In view of the characteristics of electric bus, such as large passenger capacity, large battery capacity and high driving power, the safety requirements of electric bus put forward stricter safety requirements for battery compartment collision, charging system, waterproof test conditions and vehicle requirements, increased the requirements for flame retardancy of high-voltage components and thermal runaway assessment of the minimum management unit of battery system, and further improved the risk prevention ability of electric bus.
The safety requirements of power batteries for electric vehicles not only optimize the safety requirements of battery cells and modules, but also emphasize the thermal safety, mechanical safety, electrical safety and functional safety requirements of battery systems. The test items include thermal diffusion, external fire, mechanical impact, simulated collision, damp-heat cycle, vibration soaking, external short circuit, over-temperature overcharge and so on. The standard specially adds the thermal diffusion test of the battery system, which requires that the battery system will not catch fire or explode within 5 minutes after the thermal runaway of the battery monomer, so as to reserve a safe escape time for the occupants.
In recent years, with the entry of electric vehicles into thousands of households, lithium-ion power batteries have increasingly entered our daily lives. The high energy density and long cycle life of lithium-ion batteries give electric vehicles longer cruising range and longer service life. However, as a product directly related to the safety of users' lives and property, the safety of power batteries has naturally attracted more attention.
"In the future, what attracts consumers to buy will no longer be power platoon but safety." Gao, an academician of Chinese Academy of Sciences and professor of Tsinghua University, pointed out that mileage anxiety promoted the progress of battery technology. The specific energy of lithium-ion power battery system is increasing year by year, and the cost is decreasing year by year. At the same time, the increase of specific energy of the battery also reduces the thermal stability of the material and increases the safety risk of the battery, especially how to restrain the thermal runaway of the power battery has become one of the key research topics in the industry.
The so-called "thermal runaway of the battery" simply means that when the temperature of the battery rises rapidly in a short period of time and exceeds the safe use temperature range of the battery, it will cause the thermal runaway of the battery, and then accidents such as battery burning will occur. Overcharging, lithium precipitation from dendrites, dendrites piercing the diaphragm and overheating will all induce internal short circuits. The problem of battery internal short circuit is not unsolvable, but it requires the battery management of vehicles to be gradually upgraded to a new generation of safety-oriented system, which also puts forward higher requirements for related vehicle manufacturing and battery enterprises.
Gao said that with the upgrading of the safety concept of electric vehicle power battery, two leading companies have made innovations in battery pack this year, namely CTP of Contemporary Ampere Technology Co., Ltd. and BYD's blade battery technology.
Among them, the CTP battery pack patent of Contemporary Ampere Technology Co., Ltd. cancels the battery box in the prior art, and directly installs the battery module in the whole vehicle through the sleeve through the fixing piece or the mounting beam. This design not only realizes the lightweight of the battery pack, but also improves the connection strength of the battery pack in the whole vehicle. The advantage is that it is not limited by standard modules and can improve the volume utilization rate and energy density of the system. At the same time, the heat dissipation effect is higher than that of the current small module battery pack.
BYD's "blade battery" also adopts modular battery pack technology, that is, the battery core is made into a slender "blade" shape, which increases the volume energy density of lithium iron phosphate battery by 50%; More importantly, the long core structure, the shell and the protective structure of the blade battery form a rigid structure, and the ability to resist deformation, extrusion and puncture is also stronger. In addition, the high-temperature ceramic coating with high temperature resistance and excellent insulation performance is fully used in high-risk safety places, so that the probability of short circuit inside the battery pack is extremely low.
BYD insiders told E-Cafe that the requirements of the three mandatory standards have been fully considered in the development process of blade battery. In the acupuncture test used to simulate the battery's thermal runaway, there is only a low degree of temperature change near the acupuncture point of BYD blade battery, and there is no violent reaction, which basically excludes the possibility of explosion, and even in extreme cases, there is only smoke. This also means that BYD's blade battery can better pass the thermal diffusion test of the battery system added in the Safety Requirements for Power Batteries for Electric Vehicles, and reserve a safe escape time for the occupants.
As Gao, an academician of the Chinese Academy of Sciences, said, there are three main directions for the development of electric vehicle power batteries, including the innovation of battery materials and electrochemical systems; Development of smart batteries such as intelligent manufacturing and intelligent recycling; Innovative direction of battery design and product engineering. "Blade battery" is mainly embodied in "innovation of battery design and product engineering".
Undoubtedly, the three mandatory standards are the first batch of mandatory national standards in the field of electric vehicles in China, which is of great significance to improving the safety level of new energy vehicles and ensuring the healthy and sustainable development of the industry. It is worth mentioning that people in the industry generally believe that CTP batteries and blade batteries are not completely modular, but appear in the form of large modules, but this still means that non-modular batteries have entered the accelerated stage of reform and development. It is believed that more battery companies will follow suit, bring further innovation and bring more affordable and safer new energy vehicles to consumers.
This article comes from car home, the author of the car manufacturer, and does not represent car home's position.