Recently, the terms “large cylindrical battery” and “4680” are very popular in the energy storage industry. In fact, large cylindrical batteries are not a new technology. Cylindrical batteries appeared in Japan as early as 1992. The root of this wave of craze is: Tesla regained the large cylindrical battery and gave it a size: 46mmX60mm.

The main change of the Tesla large cylindrical battery is the structural innovation. BYD’s blade battery is also an innovation in structure. The original square battery is elongated and flattened, while the large cylindrical battery is made into a “short fat man.” Can the comeback cylindrical battery break the “big knife” of the blade battery?

“Promise ear” technology is a “double-edged sword”

Cylindrical batteries used as power batteries have been developed and applied since 1992, and a variety of models have appeared since then. One of the more famous is 2170. Compared with the 2170 battery, the biggest advantage of the 4680 battery is that it is “wide and fat”. The volume of the 4680 battery is about 5.5 times that of the 2170 battery, so the capacity of a single battery will be larger.

The most prominent advantage of the 4680 battery is its large capacity and fast heat dissipation. When the battery is placed in a rectangular shape like a blade, the gap is extremely small, and when placed in a cylindrical shape, space is left, and the heat dissipation immediately becomes faster. The fast heat dissipation is actually improving the safety of the battery.

But the 4680’s fast heat dissipation is not entirely due to the shape change, but more due to the internal change. This involves the official name of the 4680 battery: “no tab battery”.

The tabs are the “ears” of the battery’s positive and negative poles. They are metal conductors that lead the positive and negative poles from the battery core, and are the contact points between the battery and the external circuit when the battery is charged and discharged. When the battery becomes “fat”, the connection between the two ears becomes longer. Because of the large capacity of the battery, the flow of electrons will cause excessive local heat at the junction of the tabs, which will bring safety hazards.

Tesla’s solution is not to eliminate the tabs, but to insert more “tabs”, which shortens the transmission distance of the electrons inside, and at the same time, the contact method of the tabs has also changed from point contact to surface contact. Greatly increase the heat dissipation area.

In other words, “non-polar ear” is actually “full-polar ear”. This brings about an increase in manufacturing difficulty. It can be said that this is an extreme manufacturing: battery companies need to weld more tabs with lasers, and the actual production requires extremely high manufacturing capabilities and equipment.

Because of this, there are still difficulties to be overcome if the 4680 battery wants to maintain a high yield. At present, Tesla has not completely solved the problem of the yield rate of the lug processing, which is why the advertised mass production time has to wait until 2022.

In addition, the large cylindrical 4680 battery is larger than the 18650 and 21700, so the radial and axial geometric symmetry become worse, and the positive and negative poles are relatively harsh inside the cylinder. Secondly, it is more difficult to dissipate heat inside the battery, which has a certain impact on battery life. Third, in situations where the rate performance is not high, the cylindrical volume energy density of CTC may also be lower than that of prismatic batteries. In other words, the 4680 battery is not without shortcomings.

The blade battery itself is lithium iron phosphate

The essence of the blade battery is the innovation of the packaging form of the lithium iron phosphate battery. The intuitive understanding is that the battery is made to a large extent and the heat dissipation of the battery is improved. Because of the application of the steel shell, the strength of the battery is increased, and the battery is packaged into a battery pack. Very important meaning, because the specific energy of the lithium iron phosphate battery is 170WH/kg. It is simpler to say that a 100 kg battery has 17 kWh of electricity. Because of the excellent design of the blade battery, after being packaged into a battery pack, the specific energy is still 140WH/ kg.

The advantage of the blade battery lies in its safety. Even acupuncture will not catch fire and explode. It is trustworthy after experimentation. In addition, the blade battery adopts CTP moduleless technology to improve the volume utilization rate of the blade battery. While maintaining high safety, it greatly improves the cruising range, and the development of lithium iron phosphate batteries has entered a new stage.

Nowadays, mainstream power battery companies at home and abroad are accelerating the pace of construction of 4680 cylindrical batteries to seize the technological high ground in advance. Perhaps this makes blade battery companies smell dangerous.

Obviously, in the market where lithium iron phosphate batteries seem to have taken the initiative, Tesla is not only making a comeback with 4680 cylindrical batteries, which brings great uncertainty to the market changes in the power battery field in the future. On this battlefield, some companies have gained new opportunities, because for domestic companies, large cylindrical batteries mean cost reduction.

Because in an electric vehicle that is also used for 75kWh, if 2170 is used, 4400 batteries are needed, while 4680 is only needed for 950 batteries. The reduction in the number of batteries means that the time required for production and assembly is reduced, and the efficiency of the group is While greatly improving, it also makes the cost more advantageous. Some experts have calculated that if the yield rate is consistent, this technology may reduce battery costs by about 7%.

On Tesla’s 2020 Battery Day, Musk said that in order to accelerate the development of electric vehicles, Tesla must produce more affordable electric vehicles. Tesla looks for opportunities to reduce costs in terms of battery design, manufacturing processes, and material systems. Today, when the material system is difficult to break through, structural innovation has become the focus of competition among major power battery companies, and the driving force behind structural innovation mainly comes from extreme manufacturing capabilities.

From the point of view of the innovation point and the difficulty of mass production of the 4680 battery, the ultimate manufacturing capacity in the future will become one of the key factors for power battery companies to win. The manufacturing capacity is exactly what the domestic manufacturing industry is good at.

4680 will bring new uncertainties to the domestic power battery market. I wonder if the blade battery is ready for the battle?