Time:2024.12.23Browse:0
China started from the Ministry of Science and Technology’s key electric vehicle projects in the “Tenth Five-Year Plan” to promote the research and development of power batteries for electric vehicles in China. At that time, they were mainly nickel-metal hydride batteries and lithium manganese oxide batteries. During the "Eleventh Five-Year Plan" period, it was mainly lithium iron phosphate batteries. By the "Twelfth Five-Year Plan", China's focus on research and development will shift to ternary lithium-ion batteries. In 2015, the specific energy of China's ternary lithium-ion batteries is expected to reach 180 watt-hours per kilogram. By 2020, it is expected to exceed 200 watt-hours per kilogram, double the current level.
Ouyang Minggao believes that compared with the world, China has many problems in electric vehicle power batteries. China’s research on advanced materials and mechanisms is poor, its battery structure design technology is less advanced, its degree of automation is also low, and its ability to develop fine processes is weak. “In the past, the electric vehicle field felt that the battery system had no technology, and it was enough to combine the monomers. , Only now do we understand that the battery system is a very complex technology."
In view of the above problems, China's supply of high-end materials is still insufficient. Consistency, yield, safety, reliability, and product performance cannot fully meet market requirements. Enterprises' overall innovation capabilities are not strong, and their advantageous production capacity is insufficient. At the same time, China's electric vehicle power batteries face challenges from foreign battery companies such as South Korea.
According to Ouyang Minggao's speculation, it is expected that by 2025, lithium-ion batteries will reach their performance limits, reaching about 350 watt-hours to 400 watt-hours per kilogram. The U.S. Department of Energy's judgment on the development status and trends of lithium-ion batteries shows that the battery limit can reach 300 to 350 watt-hours per kilogram, and can reach at least about 200 watt-hours per kilogram by 2020. China basically agrees with this judgment. The current focus of technical research is how to solve problems related to silicon anodes and improve battery life.
According to foreign trends, China's basic development goal for 2020 is for high-specific energy batteries to reach 300 watt-hours per kilogram, have a lifespan of 1,500 times, and cost 8 cents. Ouyang Minggao emphasized that in the process of moving towards high-energy lithium-ion batteries, opportunities and challenges coexist, and safety issues will become more prominent. The higher the energy ratio, the greater the challenge. "China must pay more attention to safety. Among the three issues of safety, durability and power, the core issue is safety."
The problem of power battery safety is generally called power battery thermal runaway. After the battery is heated to a certain temperature, it becomes uncontrollable. The temperature rises linearly, exceeding 500 degrees or 1,000 degrees, and then burns and explodes.
The reason is that overheating can cause this problem. Temperature can trigger side reactions in batteries, which can release heat and lead to thermal runaway. Additionally, electrical triggering can cause this problem. External short circuit, internal short circuit, and overcharge will all cause heat generation and thermal runaway. Another reason is collision. After the vehicle is collided and squeezed, the battery is like being pricked by a needle, short-circuiting, and then generating heat, which in turn causes thermal runaway.
Ouyang Minggao suggested that China should study the safety design of Tesla batteries. "It should be said that Tesla uses unsafe batteries, which are unsafe from the perspective of a single battery. However, a single unsafe battery can achieve system safety because Tesla's battery uses 7,000 Multiple 18650 ternary batteries, nickel-cobalt-lithium, and unsafe batteries alone are safe when combined. This is Tesla's safety design patent. You can analyze these patents carefully, because now Tesla's patents are all public."
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