In 2020, Tesla unveiled the epoch-making 4680 battery on Battery Day, and it was only a year after the concept of the 4680 battery was proposed. The cylindrical battery is optimized and improved, and finally I feel that the 4680 battery is a good solution.
If it is in the style of Panasonic, it will not start publicity until 2022 at least, and mass production may not start until 2025. After all, it is completely different from mass production in the laboratory, but Tesla is Dare to "blow it out", and this time it seems to have blown it again. Celebrating Tesla's California factory pilot producing 1 million 4680 cells, which can hold roughly 1,000 Model Ys
At the just-concluded EV 100 Conference 2022, major battery giants such as Panasonic, BAK Battery, and Yiwei Lithium Energy expressed their optimism about the 46-series large cylindrical battery. At the same time, in January, Tesla announced the factory in California. One million 4680 batteries have been pilot-produced in China, and the official loading of 4680 batteries is close at hand.
The 4680 battery is a cylindrical battery with a diameter of 46 mm and a height of 80 mm. The 18650 and 2170 batteries currently used by Tesla also conform to this naming rule. The last "0" of the 18650 battery means a cylinder, but the 2170 and 4680 batteries Omitted.
First of all, let’s look at the diameter of “46 mm”. From the perspective of safety, although the reduction of the number of battery cells in the whole vehicle can reduce the difficulty of BMS management, the heat dissipation of large cells is a problem, and 46 mm is a point within the balance range. From the perspective of improving battery life and reducing costs, Tesla believes that after 46 mm, the battery life of the entire vehicle begins to decline, and the marginal benefit of cost reduction becomes very low, so 46 mm is the optimal solution. In addition, from the perspective of internal stress, 46 mm is also a relatively critical point. Before there is no essential breakthrough in chemical properties and production processes, 46 mm is a golden size.
Another parameter is the height of "80 mm". In fact, the industry has not yet concluded, mainly due to the different chassis designs. For example, BMW uses the 4695 scheme, and some manufacturers plan the 46105 scheme, that is, the height is 105 mm. But this height should not be too high. On the one hand, radial heat dissipation will be a problem, and on the other hand, it will significantly increase the thickness of the chassis, which will affect the design aesthetics and wind resistance.
Simply put, it is path dependence. Tesla was established in 2004 and launched its first model Roadster in 2008. At that time, there was no very mature power battery solution available on the market, and Panasonic's 18650 battery was very mature, stable and safe in the civilian field. The reliability and consistency have reached a very high level, so Tesla chose the solution of using thousands of single cells to assemble. Although the test for BMS was relatively large, it was indeed more reliable than other power battery solutions at that time. spectrum.
Tesla Model S battery pack, consisting of thousands of 18650 cells
With the development of power batteries, 18650 batteries have been gradually upgraded to 2170 batteries. Tesla and its suppliers Panasonic, LG Chem, etc. are becoming more and more specialized in cylindrical batteries, but this time 4680 batteries are also a time for cylindrical batteries. Squeeze the toothpaste upgrade.
02. Toothpaste squeezed out, the core technological innovation of Tesla's 4680 battery
Tesla Battery Day PPT, 4680 battery has 54% longer range and 56% lower cost than 2170 battery
The upgrade from 18650 to 21700 can be seen from the numbers that it is a bit like squeezing toothpaste, a bit like the Qualcomm Snapdragon chip in the past two years, and the 4680 battery is not only 448% larger than the 2170 battery, but more Combined with revolutionary technologies such as all-pole tabs, high-silicon anodes, and combination with CTC, finally, the battery life increased by 54%, the cost decreased by 56%, and the investment in equipment per unit capacity decreased by 69%. Of course, Tesla's PPT has always been a little watery, which should be achieved after two or three iterations of the 4680 battery).
Full polar ear: drive farther and charge fast
The traditional battery has a very big limitation: the energy density and power density cannot be balanced. For example, the energy density of the ternary battery of the Honda Accord hybrid is only 82 Wh/kg, while the energy density of the ternary lithium battery of the pure electric vehicle is average. At 150-180 Wh/kg, this is because the core parameter of HEV lithium battery is power density. After all, the battery is small (the battery capacity of the Accord Hybrid is only 1.3 kWh) and it needs to drive a high-power motor, so it can only sacrifice some mass energy density .
Under the all-pole scheme, the path of electron flow is significantly shortened
The Tesla 4680 battery combines the two by adopting the solution of all-pole ears (Tesla advertises that it is a pole-less ear). The pole ear is simply the contact point when the positive and negative electrodes are charged and discharged. The traditional battery is in the positive and negative electrodes. Each has a pole ear, which brings a problem. When the current flows from the positive pole to the negative pole, as shown on the left side of the above figure, it has to cross a long horizontal path, so that the internal resistance naturally rises, which not only consumes the energy of the battery, but also generates heat. difficult to resolve.
According to Tesla's patent, it can be seen that the positive and negative poles of the 4680 battery are evenly distributed, which greatly shortens the distance between the poles. , the path is about 900 mm, and the positive and negative films of the 4680 are 4-5 times that of the 2170 battery. If the monopole is still used, the path of the electrons will be as long as 3.8 meters, and the internal resistance will also increase by 4 times. The pole ear solution can shorten this path to the height of the battery, which is 80 mm. According to Tesla, the internal resistance of the 4680 battery is only one-fifth of that of the 2170 battery. Combined with the full tabs, the current path is greatly increased so that electrons can move more easily inside the battery.
Under the V3 overcharge, the estimated charging speed of the 4680 battery is faster than that of the 2170 battery, and the difference is expected to be more obvious under the V4 overcharge
Therefore, the full-ear 4680 battery has the talent of high-power discharge and overcharge. According to the research report of Insideevs, it takes 15 minutes for the 400 V 4680 battery system to charge 70% of the power, while the Porsche Taycan and Hyundai using the 800 V battery system IONIQ by car takes 18 minutes and 22 minutes respectively. In the future, if the 4680 battery adopts an 800 V voltage system, the charging speed will be faster.
High nickel cathode + high silicon anode: the key to single energy density reaching 300 Wh/kg
At present, Tesla's 4680 battery positive electrode still uses the NCM 811 high-nickel solution, which everyone is familiar with. In the future, the 4680 positive electrode will use a higher proportion of nickel (such as NCM 9/0.5/0.5) and "cobalt-free". and "quaternary" aspects of evolution.
The change in the positive electrode is not large, and the negative electrode is also very critical to achieve higher energy density. At present, most batteries are graphite negative electrodes, but the theoretical specific capacity of graphite is 372 mAh/g, which has actually reached about 330-370 mAh/g, which has reached the ceiling. The specific capacity of silicon can reach 4,200 mAh/g, which is more than 10 times that of graphite. Therefore, doping a certain proportion of silicon in the negative electrode has always been the direction of battery energy density breakthrough.
On 2020 NIO DAY, the PPT of NIO's 150-degree battery shows the silicon carbon negative electrode and the high nickel positive electrode, to achieve high energy density, everyone has the same goal.
In fact, as early as 2017, on the Model 3 equipped with 2170 batteries (from Panasonic), Tesla has introduced the technology of "silicon doping", but the proportion is still relatively small (about 5-6% of silicon alloy), The increase in energy density is not yet obvious. There are also some domestic manufacturers that have adopted "silicon-doped" negative electrodes. For example, the negative electrode of the large battery of GAC Aeon LX 144.4 degrees with a CLTC battery life of 1,000 km is doped with a certain proportion of silicon. The 150 kWh "solid-state" battery mass-produced in Q4 also uses this technology.
Relatively speaking, the stress inside the cylinder is uniform in all directions
Relatively speaking, the structure of the 4680 battery is more suitable for "silicon-doped". First of all, the characteristics of the winding of the pole piece of the cylindrical battery can make the expansion force of each position of the pole piece as uniform as possible, and reduce the appearance of damage and wrinkles. Damage and wrinkles caused by stress concentration are prone to occur at the place. In addition, the stainless steel shell of the 4680 battery has high mechanical strength and can fully absorb the expansion force of the negative electrode. Therefore, in theory, more silicon can be doped into the negative electrode of the 4680 battery, which is expected to reach more than 10%, and the energy density will be significantly improved.
Starting from first principles, in order to improve the energy density of the battery pack, the less "middleware" the better, for example, if you want to put the most eggs in a box, it is best to remove the egg tray, which is equivalent to It is more extreme to remove the mold components, and the box is not needed, that is, the CTC (Cell to Chassis) technology, and some are called CTV (Cell to Vehicle).
4680 battery combined with CTC technology, seat mounted directly above battery
The 4680 battery is born with this potential. First of all, CTC has certain requirements for the structural strength of the battery. The battery itself has to bear a lot of mechanical strength. Compared with the 18650 and 2170 batteries, the 4680 single battery has a larger structural strength and higher strength. And the general square shell battery is aluminum shell, and the 4680 shell is stainless steel, the inherent structural strength is guaranteed. In addition, the use of CTC technology basically means saying goodbye to maintenance and replacement. If there is a violent collision or there is a problem with the consistency of the battery, it may only be possible to change the car, and the consistency of the cylindrical battery has always been an advantage. Finally, compared with the square shell battery, the layout of the cylindrical battery will be more flexible and can adapt to various chassis. Combined with the advantages of high energy density and high charging and discharging power of all-pole tabs, the future potential in the field of HEV and PHEV is also very large.
In addition to all-tab batteries, high nickel + high silicon and CTC technology, Tesla 4680 batteries also have other technical applications, such as applying PVDF on the diaphragm to prevent the expansion of the silicon negative electrode, adding silicon nanotubes to the negative electrode to improve conductivity, and in addition Tesla's second-generation 4680 battery may also use the dry electrode process. In short, Tesla is going to squeeze the toothpaste this time, it depends on how the opponents take the trick.
03. 4680 cylindrical battery VS CTP square battery, is the Ningde era in danger?
The square battery in the Chinese market stands out, and the cylindrical, square and soft packs in the overseas market are three pillars.
The data shows that since 2019, square batteries in China's power battery market have been occupying about 80% of the market share, and the Ningde era has accounted for more than half of them. Naturally, the first impact of the 4680 battery is also the Ningde era.
Here, we will first put aside the domestic soft-pack batteries that mainly focus on European customers such as Mercedes-Benz, and focus on comparing the advantages, disadvantages and development trends of CTP square batteries and 4680 cylindrical batteries.
4680 battery arrangement
First of all, the group efficiency of square cells is obviously better than that of cylindrical cells. It is expected that excellent CTP cells can reach 80%-90%, and 4680 + CTC can reach more than 70%. This is not difficult to understand. Although the 4680 battery is much larger than before, it is still very small compared to the large square battery. About 960 4680 batteries are needed on a Model Y, and it may only take 6 to 10 to replace the square case. The lower the proportion of other components not related to chemical substances.
Volkswagen's CTP ternary prismatic battery pack
However, since the single cell of the square battery is large and is in surface contact, it is very difficult for the heat dissipation and thermal runaway protection of the square battery. Therefore, the positive electrode of the square battery ternary battery is not suitable for the direction of ultra-high nickel. At the same time, it is mentioned that the negative electrode of the square battery is not suitable for adding too much "silicon", so the single energy density of the square battery cannot be made too high.
The cylindrical battery is relatively easy to dissipate heat because of its small single cell. In addition, the application of all-pole tabs makes it easier to dissipate heat in a targeted manner. Therefore, a more aggressive high-nickel solution can be used, combined with a high-silicon negative electrode. The energy density of the monomer can reach 300 Wh/kg. In the future, if a positive electrode with a ratio of more than 90% nickel is used, the energy density of the monomer can reach 350-400 Wh/kg.
In this way, although the integration efficiency of the square battery is high, the single energy density of the 4680 cylindrical battery is high. In summary, the system energy density of the two is similar.
As a variety that has been commercialized for more than 30 years, cylindrical batteries have the most mature technology and certain advantages in terms of production efficiency, yield, and investment cost. For example, in terms of yield, Panasonic's 2170 battery can reach more than 99%, which is already a very good level compared to square batteries that can reach 90%.
In addition, in terms of production efficiency, if the winding process is also adopted, the innate efficiency of the concentric winding of cylindrical batteries is much higher. For example, according to the latest production line of Yiwei Lithium Energy, 200 2170 batteries can be produced per minute, while
Similar production lines of prismatic batteries within 200 Ah can generally produce 10-12 cells per minute, and large cells over 200 Ah can produce less than 10 cells per minute. If it is a new car equipped with 80 kWh of electricity, the production of cylindrical batteries takes about 20 minutes, while the production of square batteries takes 30 minutes.
If the mass production of 4680 batteries goes smoothly, it is estimated that after 2024, the cost of 4680 batteries per kWh is 50-100 yuan cheaper than that of ternary prismatic batteries, and the cost of an electric vehicle with a 100-degree battery can be 5,000-10,000 yuan lower.
Therefore, from the perspective of the ternary battery system (including cobalt-free batteries and quaternary batteries), if the yield of the 4680 battery can be rapidly improved, it will rely on a certain cost advantage and ultra-high charge and discharge power. It will gradually form a substitution effect on the square ternary lithium battery.
In the low-end market, lithium iron phosphate batteries are still dominated. Lithium iron phosphate is inherently stable and not prone to thermal runaway, so it is more suitable for square batteries with high integration efficiency but not easy to dissipate heat. Therefore, the future situation is likely to be that some high-end models begin to gradually use 4680 ternary batteries, while the mid-to-low-end models are dominated by CTP square lithium iron phosphate batteries.
BYD blade battery, the blade battery on the Han EV also adopts the lamination process
Then the Ningde era will face the attack of 4680 batteries and BYD blade batteries. BYD itself started with batteries, and has been specializing in lithium iron phosphate batteries for many years. As the production capacity of Fudi batteries begins to expand significantly, here You can refer to the article, which is bound to eat up part of the share of the Ningde era.
The Ningde era CTP 3.0 Kirin battery advertises that the system energy densities of ternary lithium and lithium iron phosphate can reach 250 Wh/kg and 160 Wh/kg respectively, and can achieve the highest safety requirements without thermal diffusion
However, at the just past 100-person meeting of electric vehicles in 2022, Ningde era also gave a counterattack - whether the Kirin battery of the CTP 3.0 version can maintain its current absolute leading position, it depends on the landing effect of CTP 3.0 and the cost reduction and efficiency increase. speed.
04. Which car companies and battery factories are following up the layout of large cylindrical batteries?
At present, from the perspective of car companies, the main driver is still Tesla. In 2022Q1, Tesla has started trial production, and it may be able to deliver a small amount of 4680 Model Y to consumers by the end of the year. The real outbreak period will be after 2023, when the long-delayed Cybertruck and heavy truck Semi will gradually meet with you. The mass production time given by BMW's 4695 battery is after 2024, and it may become the main battery of BMW's future pure electric platform "Neue Klasse".
Lucid, a new American car-making force, also uses 2170 cylindrical batteries
In addition, there are already many overseas manufacturers that use cylindrical batteries. For example, the new forces in the United States, Lucid and Rivian, currently use 2170 batteries, and it is very natural to transition to 4680 batteries in the future. LG Chem's global share in the power battery field is second only to the CATL era
On the battery manufacturer side, overseas are mainly Tesla, Japan and South Korea battery manufacturers, including Panasonic, LG Chem, Samsung SDI, Panasonic and LG Chem plan to mass production in 2023, Samsung SDI plans to mass production in 2024, and there are An Israeli company, Storedot, also plans to mass-produce 4680 batteries in 2024.
The domestic CATL currently plans a 4680 battery capacity of 12 GWh, and the pace of research and development is accelerating. It is expected to start mass production in 2024. The customers may be Tesla and BMW; BAK battery will be displayed at the Shenzhen CIBF in March 2021. Cylindrical products are expected to be mass-produced in 2023; Yiwei Lithium Energy is expected to achieve mass production of 4680 batteries in 2024, with a planned production capacity of 20 GWh, and there is also a plan to build a factory in Hungary, Europe.
On the whole, compared with the upgrade from 18650 to 2170, the 4680 battery squeezed the toothpaste this time, which basically determined the development direction of cylindrical batteries, and is also expected to lead the market share of cylindrical batteries to quickly catch up with square batteries. However, the 4680 battery still faces many process problems. For example, the laser welding point of the full-tab battery is at least five times that of the 2170, which requires very high precision. At the same time, the curved edge of the full-tab coating also requires higher precision of the equipment. In the future, the development of 4680 batteries will focus on when the yield rate of Tesla, Panasonic, LG Chem and other companies can stabilize above 90%.
