Is the lithium iron phosphate battery fast charging solution better than ternary lithium?

　　If new energy vehicles want to truly achieve a similar experience to traditional gasoline vehicles, shortening the charging time, improving the range and convenience of charging are unavoidable topics.

　　If new energy vehicles want to truly achieve a similar experience to traditional gasoline vehicles, shortening the charging time, improving the cruising range and the convenience of charging are unavoidable topics. Dr. Wang Shengwei, head of the fast charging project of CATL New Energy Technology Co., Ltd. (CATL), said that the "superconducting subnet" and "fast ion ring" technologies developed by CATL are combined to develop lithium iron phosphate fast charging cores. After having 4C high-rate fast charging, 100% charging of pure electric buses can be completed within 15 minutes.　　 Recently, Wang Shengwei delivered a speech to analyze the principles and characteristics of fast-charge lithium-ion batteries, and introduced CATL's maintenance plan and the progress of fast-charge lithium-ion batteries.　　 In principle, the bottleneck of fast charging of batteries is the negative electrode. Common chemical systems will produce by-products on the negative electrode during fast charging, which will affect the cycle and stability of the battery. Once the lithium ions are blocked in the negative electrode, it is very dangerous, but as long as the lithium ions enter the graphite, there is basically no problem. Therefore, CATL has developed the "fast ion ring" technology to create a highway network on the surface and inside of the graphite, so that lithium ions can be quickly embedded in any position of the graphite. "It can achieve both lithium ion density and fast charging. This is like repairing the ring road to alleviate traffic congestion. The'fast ion ring' graphite is the mechanism. We have shipped hundreds of millions of dollars on mobile phones. It is reliable. Sex has been verified.” Wang Shengwei introduced.　　 Is lithium iron phosphate suitable for fast charging?　　 Some people in the industry believe that lithium iron phosphate is not suitable for fast charging. In Wang Shengwei's view, this problem has two sides. From the point of view of materials, the intrinsic conductivity of lithium iron phosphate materials is relatively low, only one percent of that of ternary materials. It is necessary to optimize the conductivity of lithium iron phosphate materials to meet the needs of fast charging.　　Wang Shengwei said that after CATL's transformation, lithium iron phosphate is no longer "the original lithium iron phosphate", even better than ternary materials. On the positive electrode, CATL has developed the "superconducting subnet" technology, which makes lithium iron phosphate have excellent electronic conductivity, which can reach 1000 times that of ternary materials.　　 He pointed out that the current cycle performance of lithium iron phosphate fast-charged batteries is better than that of non-fast-charged batteries. In principle, there is no contradiction between cycle performance and charging. Then why is it not good for a traditional battery to use a fast charge cycle? That's because traditional batteries are not designed for fast charging. There will be by-products or side reactions during fast charging. When the side reactions increase, the cycle will naturally deteriorate. Once the kinetic problem of fast charging is solved, its cycle will not deteriorate at least. At the same time, fast charging batteries not only have higher kinetics, but also because the energy density is lower than that of non-fast charging, it is not surprising that the energy density is lower, the electrolyte is more, and the circulation becomes better. In fact, the lithium iron phosphate fast charge battery they are currently developing can reach 10,000 cycles. To ensure fast charging in the "healthy charging range" "After years of research at CATL, we believe that the healthy charging range is related to the irreversible reaction speed of charging. For a fixed chemical system, it will be affected by temperature and voltage and is irreversible. The speed of the reaction determines the speed of the capacity decay and impedance increase of the battery during the cycle. Therefore, the focus of our research is how to identify the speed of the irreversible reaction. Fast charging can be achieved within this "healthy charging interval". Charging can prevent the battery from being damaged by fast charging, and achieve both fast charging and long cycle.” 　　 In low temperature conditions, CATL proposes two battery protections. One is charging in a temperature range and slow charging at low temperatures. Charge in the "healthy charging interval" to better protect the battery. The second is to use the hydrothermal system to heat the battery cell at low temperature. When the battery cell temperature reaches the required level, the fast charge mode can be turned on to achieve "healthy" fast charge at low temperature.　　 Similarly, the battery also needs to avoid the effects of high temperature, because it has an oxidation-reduction reaction, the higher the temperature, the more violent the reaction. In this regard, CATL's solution is to use a low voltage system of 3.65V, which has weak positive oxidation, few side reactions and slow speed. In addition, there is water cooling to control the temperature to avoid high temperature.　　High-energy-density battery fast charging leads the world. 　　In terms of “longer cruising range”, CATL’s technical plan is to achieve a battery energy density of 300 watt-hours per kilogram by 2020. After 2025, there are plans to further increase the energy density. In terms of "shorter charging time", CATL has been developing a fast-charge battery with an energy density of 190Wh/kg and a 15-minute full charge. The battery is expected to have mass production capacity in 2018, and its main application area is passenger cars. "For the high-energy density fast-charging batteries for small cars, we have the advantage of technical reserves, and domestic battery companies have the opportunity to be ahead of Japan and South Korea." Below 1C, charging to 80% is close to 50 minutes. Our product can charge 80% in 12 minutes, and the charging speed is in sharp contrast. Even for the heavy-duty taxis with fast charging, they are fully charged twice a day, one It needs to be charged 700 times a year. According to the taxi's 4 years of service cycle, 2800 times should be enough. The cycle of our high-energy fast-charge battery is expected to be more than 3000 times, which should be able to meet the needs of passenger car applications. ."