On June 23, 2022, CATL officially released the CTP3.0 battery, the Qilin battery. Qilin batteries are not battery cell technology, but battery system technology. This is a battery system composed of prismatic cells, the volume utilization rate has exceeded 72%, and the system integration has reached a new high in the world. When using ternary material cells, the energy density of the Qilin battery system can reach 255Wh/kg, which can easily achieve a 1,000-kilometer battery life of the vehicle. When using lithium iron phosphate, the system energy density also exceeds 160Wh/kg. What is the difference between Tesla 4680 battery vs CATL CTP battery? Under the same cell chemistry system and the same battery pack size, the energy density of the Qilin battery is 13% higher than that of the cylindrical 4680 battery system.
1.CATL prismatic Qilin battery optimizes the battery structure
One of the biggest features of Qilin batteries is the inversion of the cells. CATL is not the first company to put effort into battery cell placement. Not long ago, SAIC released a battery pack for laying cells. The way of inverting the battery cells in the CATL is obviously more efficient than the lay-type battery pack. The two have the same idea of adjusting the water-cooled functional parts, and they are both moved from the bottom to the middle of the battery. CATL also integrated water cooling, heat insulation and transverse beams, further improving the integration of battery packs.
① The cell space utilization rate reaches 72%
It can be seen from the information given by the CATL that the cells are inverted.It turns out that when the top cover is placed upwards, the battery pack needs to leave space for both the top and bottom of the cell, the top for thermal runaway, and the bottom for preventing bottom ball hits. Nowadays, the cells are upside down, and the uncontrolled exhaust and the bottom ball strike space are shared, leaving 6% more space for the cells. Compared with the Rubik's Cube battery, the space utilization rate is higher.
② Integrated into a multifunctional elastic interlayer
CATL also canceled the original independent design of transverse beams, water-cooling panels and thermal insulation pads, and integrated them into a multi-functional elastic interlayer.The built-in micron bridge connection device can freely expand and contract with the respiration of the cell, improving the reliability of the cell throughout its life cycle. The benefits of this interlayer are not only that, but also play the role of a force-bearing structure. The battery cell and the multi-functional elastic interlayer form an integrated energy unit, which becomes a force-bearing structure in the driving direction, improving the structural strength and impact resistance of the battery.
③ The heat exchange area is expanded by four times
CATL quadrupled the heat exchange area by placing the bottom water-cooled functional parts between the cells. The large-surface cooling technology of the battery reduces the temperature control time of the battery to half of the original, so as to adapt to the fast charging of higher current and higher voltage. At present, the Qilin battery can support fast hot start in 5 minutes and fast charge to 80% in 10 minutes. In extreme cases, the cells can be rapidly cooled, effectively blocking the abnormal heat conduction between the cells, effectively avoiding irreversible damage caused by the abnormal working temperature of the battery, and effectively improving the life and safety of the cells.
Therefore, Qilin batteries can achieve thermal stability and thermal safety of the full chemical system, thus adapting to material upgrades with higher energy density. The substantial increase in the cooling area effectively adapts to the launch of the next 800V voltage platform models by car companies. It can be said that CATL made the best use of every inch of space in the battery pack through a large amount of real vehicle data and AI simulation. At present, for high-end 800V platform models, only the cylindrical 4680 battery system can compete with Qilin batteries. But Tesla 4680 battery vs CATL CTP battery, which one is better?
2.Mass production of Tesla 4680 cylindrical cells faces many challenges
In theory, the technical maturity of cylindrical cells is the highest, but in fact, compared with 18650 and 21700 battery, 4680 is very difficult to mass produce. In the eyes of industry insiders, although Tesla's small cylinder has rich experience, the experience is basically not available on the 4680, because the 4680 requires a number of innovative technologies to be applied together. Generally speaking, the 4680 must choose the full tab (tabless) technology. The conventional monopole ear cannot solve the problem of hot spots, and it cannot meet the needs of high power.
① Mass production is difficult
The first difficulty is that the precision of the winding machine is higher. Alignment is also more difficult due to the larger cell size. The second difficulty is the welding technology of the tabs. Currently, the production process of full pole ears includes cutting and stacking method and kneading method. The cut-and-stack method is a solution adopted by Tesla. It is mainly rolled up by obliquely cutting the sheet, and the surface fluctuation is large, which is easy to cause the poor consistency of the internal resistance of the tabs due to the inconsistent degree of contact.
In addition, when the electrolyte is injected, since both ends are closed by the tabs, continuous injection production cannot be performed. The kneading method is a full-tab solution that is widely used by Chinese companies. The tabs are rubbed into end faces through ultrasonic waves or machinery. During the flattening process, the tabs are prone to produce metal debris, which leads to excessive self-discharge of the cell, and even an internal short circuit. In addition, the rear end surface of the flattening is relatively dense, and it is difficult for the electrolyte to enter the inside of the cell. These will become a problem to improve the cell yield rate.
② Low space utilization
Under the same chemical system, the space utilization rate of large cylindrical cells is much lower than that of prismatic cells. If the ternary material is also used, the prismatic can use ordinary 532 or 622 material, but the 4680 must use high nickel to have similar power. Although high-nickel ternary has high energy density, it also means a higher risk of thermal runaway, which must be paid attention to at the system protection level.
③ The traditional method is difficult to dissipate heat
At present, cylindrical cells all use side cooling. Cylindrical cells generally have the fastest heat conduction in the axial direction and the slowest heat dissipation on the side. This feature of 4680 large cells is more obvious. Under 800V high-voltage charging, the battery will accumulate a lot of heat in a short time, and the side heat dissipation speed will be slower. In the long run, it will have a greater impact on the life of the battery. The way Tesla adopts is to add a water cooling plate on the top to achieve the effect of bilateral cooling on the side and the top.
④ The scale effect is difficult to exert
If car companies do not have the grouping technology of cylindrical batteries, and rely on battery companies to manufacture battery systems, it is difficult to exert the scale effect.
⑤ Insufficient anode material
The anode of 4680 should use silicon carbon to reflect the significance of energy density improvement. However, the silicon carbon anode should have some disadvantages. First, the cost is high; second, there are many side reactions, high expansion, and low first charge and discharge efficiency, which affect the quality of the battery; the third is that under the influence of silicon volume change.
The SEI film is repeatedly destroyed and reformed, and lithium ions are consumed in large quantities, which may reduce the cycle characteristics and battery capacity. Therefore, although 4680 cells have outstanding advantages in terms of energy density and fast charging performance, they have great security challenges, and the production difficulty has increased exponentially. Moreover, for car companies, the grouping of cylindrical batteries is very difficult. If the grouping technology of cylindrical batteries is not available, its cost advantage is difficult to exert.
3.The group performance of 4680 cells may not be as good as the CTP battery system
What is the result of Tesla 4680 battery vs CATL CTP battery? The 4680 cells with better single performance seem to be inferior to Qilin batteries after grouping. From the data given by CATL, the cylindrical 4680 system is still slightly insufficient compared with Qilin batteries in terms of energy density, fast charging performance, integration and thermal conductivity. Before the release of CTP technology in CATL, the only way for battery companies to improve energy density was to explore in terms of cell size and material system. However, the change of the material system is a very slow process, which needs to constantly balance the performance of the cells, and it takes several years or even more than ten years of research and development to mature.
However, the simplification of the structure of the battery pack in the CATL has opened up an innovative path: first, the energy density is higher. The energy density of the lithium ion battery pack can be greatly improved by simplifying the structure without changing the material of the battery core, the difficulty is relatively lower, and the iteration speed of the battery energy density is faster. The second is relatively safe. Compared with the battery itself, the energy density is improved by increasing the nickel content, the stability of the battery is guaranteed, and the safety of the battery system is also improved to a certain extent. From this, in Tesla 4680 battery vs CATL CTP battery, CTP seems to be better.