CATL's fast charge, the big reveal of lithium battery fast charge technology

　　CATL's fast charge, lithium battery fast charge technology is a great secret. What is fast charging technology? What is the principle of fast charging technology? Where is the technical difficulty? Today I am very honored to invite CATL "Quick Charge King" Wang Bo to explain the fast charge technology to everyone.

　　What is fast charging technology? What is the principle of fast charging technology? Where is the technical difficulty? Today I am very honored to invite CATL "Quick Charge King" Wang Bo to explain the fast charge technology to everyone.

　　Wang Bo, the first person to research lithium battery fast charging technology in China, has eight years of fast charging technology research and development experience. When you see "Charge for 5 minutes, talk for two hours", you think of Wang Bo's knowing smile.

　　To understand fast charging, there is no escape from a technical term. What is C! C? C refers to the charge rate, which can be simply understood as the rate of charge and discharge. The charge-discharge rate of lithium-ion batteries determines how fast we can store a certain amount of energy in the battery, or how fast we can release the energy in the battery.

　　For example, for 1C current, it takes 1/1=1 hour from full charge to discharge; 2C=1/2 hour, which is 30 minutes; 4C, it takes 15 minutes.

　　Fast charge and slow charge are relative concepts. The industry generally believes that fast charging of electric vehicles refers to a charging method with a charging current greater than 1.6C, that is, a technology that takes less than 30 minutes to charge from 0% to 80%.

　　If we visually compare a lithium-ion battery to a rocking chair, the two ends of the rocking chair are the two poles of the battery, and the lithium ion is like an excellent athlete running back and forth on both ends of the rocking chair.

　　When charging, lithium ions are generated on the positive electrode of the battery, and the generated lithium ions move to the negative electrode through the electrolyte. The carbon as the negative electrode has a layered structure, which has many micropores for the insertion of lithium ions that reach the negative electrode. The more lithium ions are inserted, the higher the charging capacity.

　　During fast charging, lithium ions need to be accelerated and inserted into the negative electrode instantaneously. This poses a great challenge to the negative electrode's ability to quickly receive lithium ions. The battery of ordinary chemical system will have by-products in the negative electrode during fast charging, which will affect the cycle and stability of the battery.

　　Therefore, the core of the lithium battery fast charging technology is to accelerate the speed of lithium ions moving between the positive and negative electrodes through chemical system and design optimization without affecting the battery life and reliability.

　　The diffusion and movement of lithium ions between the positive and negative electrodes is the same as the one-hundred-meter race. We hope that the runways should be wide enough and not crowded with each other. How to widen the channel?

　　For this reason, on the graphite surface of the negative electrode, CATL uses the "fast ion ring" technology, which is equivalent to creating a high-speed track on the graphite surface, which greatly accelerates the insertion of lithium ions in the graphite layer. The modified graphite takes into account both super fast charging and high Characteristics of energy density.

　　There are no by-products in the negative electrode during fast charging, which greatly improves the insertion speed of lithium ions in the graphite layer, so that it has a 4-5C fast charging capacity, and realizes fast charging in 10-15 minutes.

　　In addition, the heat dissipation rate inside the battery is also an important factor affecting the rate performance. If the heat dissipation rate is slow, the heat accumulated during high-rate charging and discharging cannot be transferred out, which will affect the reliability and life of the lithium-ion battery.

　　The fast charging products currently developed by CATL are equipped with a self-developed thermal management system, which can fully identify the "healthy charging range" of a fixed chemical system at different temperatures and SOCs, greatly expanding the operating temperature range of lithium batteries.

　　When the southern summer is very hot, the battery system automatically sends out a cooling demand, and the water cooling system is activated to cool the battery core, so as to achieve "full climate" fast charging.

　　When the battery is in the cold winter in the north, the water heating system heats the battery cell at low temperature. When the battery cell temperature reaches the required level, the fast charge mode is turned on.

　　At present, CATL super iron lithium fast charging products have been applied in batches in the field of commercial vehicles, which can achieve 85% full charge within 10 minutes, and the cycle life can reach more than 10,000 times. More than 2,600 electric buses equipped with CATL super fast charging products have been in operation on the market, and they are operating in good condition and have been well received by vehicle companies and bus users.

　　The fast charging technology of 　　 passenger cars can also achieve 350 kilometers of battery life and complete charging within 15 minutes. At present, many passenger car companies are cooperating with CATL to develop fast charging products.

　　However, for the popularization of high-power fast charging, there are still many difficulties that must be overcome one by one in the upstream and downstream of the industry chain.

　　01

　　Impact of infrastructure

　　The power of fast charging can reach 350kW, which imposes a heavy burden on the existing power grid and may affect the stability of the power grid. At the same time, due to the lag in the design and laying of infrastructure, it may have a certain impact on the promotion of fast charging.

　　Standardization and voltage power rating

　　02

　　Generally speaking, fast charging uses DC charging, which are basically public facilities. In this way, different manufacturers should adopt the same charging protocol and standard, so that public facilities can be better used.

　　03

　　The challenge of electrical systems

　　With the increase of battery voltage, the power devices of power electronics in vehicles are new challenges. Due to technological limitations, only some foreign manufacturers can provide related products. This poses a challenge to patents and the cost of the entire vehicle.

　　Challenges of thermal management during charging

　　04

　　The high current of fast charging and the large heat generated by the battery and charging system are a big challenge to the thermal management system of the vehicle. Improve the efficiency of thermal management, and explore the use of direct cooling in the vehicle and off-board cooling systems. Possible challenges.

　　You have to accept these quick charging tips

　　Is there any scientific basis for fast-charging batteries?

　　What are the consequences of injury?

　　Every battery of the same design has a "healthy charging interval", and the chemical system of fast charging batteries is specially optimized. Its "healthy charging interval" is larger than that of slow charging batteries, and the charging current it can withstand is naturally greater than Slow-charge batteries must be large.

　　Therefore, if you use a system-optimized fast-charge battery, its life will not be affected. However, if the slow-charge battery is forced to be used as a fast-charge battery, because the charging current exceeds the healthy charging interval of the slow-charge battery, the battery will suffer relatively serious damage and its life will be greatly shortened.

　　After years of research, CATL has found that the healthy charging interval is related to two factors, one is temperature and the other is SOC (the state of charge, the level of voltage). So just identify the healthy charging interval of each battery and perform fast charging within the range. It can be charged quickly without harming it.

　　How often do you use fast charging

　　There is no strict limit, it depends on the user application scenario. Taxi companies have purchased electric cars and use electric cars as a means of production. They have strict requirements on the charging speed, so there is no ceiling. On average, taxi users charge once or twice a day, fast charging during the day and slow charging at night. This can not only meet the needs of taxi operations, slow charging at night is also helpful for fast charging cycles, and at the same time can take advantage of the peak-to-valley price difference.

　　The daily mileage of private car owners is less than 50 kilometers, and they generally use slow charging. For private car owners, fast charging is generally based on emergency charging.

　　Eat 80% full

　　Is the fast charge to 80% less harmful to the battery?

　　The battery has an effective volume, and the effective volume is generally reached when it reaches 95%. If the battery is fully charged every time, the battery will be in a full-load working state, and the battery will be exhausted in the long run. The last trickle part of the fast charge can be omitted, because the current will be very small at the end of the charge. Since it is not a constant voltage, the voltage will be very large at this time, so the efficiency of the final charge is very low. It is better to just let the battery eat each time. To 80% full. On the contrary, the battery will be in a very healthy state, which is the same as people eating.