Tesla 4680 battery – technology innovation and industry chain development

Tesla 4680 battery is one of the most groundbreaking technologies of Tesla, and its excellent performance in the field of electric vehicles makes it a key technology leading the development of the lithium battery industry, bringing revolutionary changes, and a number of advantages of this battery open a new prospect for the future development of electric vehicles.
Table of Contents

What is 4680 battery

“4680” represents the size specification of the diameter and height of the battery. The 4680 battery refers to the diameter of the battery is 46 mm and the height of 80 mm. Compared with the traditional electric vehicle battery, its larger volume, higher capacity and higher energy density can provide longer driving range and batter performance.

Advantages of 4680 battery

Compared with the 21700 battery single-pole lug structure, the 4680 battery adopts the design of all-pole lug+collector plate, while the mainstream scheme adopts the new configuration of the positive pole at the bottom of the shell groove and the cover plate laser welding to seal the shell groove.

In terms of processing process, compared with 21700 battery, 4680 battery increased the pole lug die-cutting, kneading, laser welding collector, opening formation, laser welding cover plate process, 4680 battery cell capacity is 5 times that of 21700 battery, which can improve 16% of the mileage of the corresponding model, and the output power is 6 times higher than 21700 battery.

At present, Tesla 4680 battery has self-produced 1 million batteries in January 2023, with an average yield of 92% and the highest yield of 97%, and the yield has reached the mass production level.


Two structural schemes of 4680

Traditional scheme: the end of the negative lug faces the bottom of the steel shell groove, and the positive lug is led out from the open end and welded with the positive end. The steel shell base is welded with the negative all-pole lug through the groove by pulsed laser penetration welding.

●Advantages: the structure without negative collector does not occupy the space in the height direction of the steel shell, improving the space utilization rate;

●Disadvantages: when the battery wall thickness increases, it is difficult to weld the pole lug firmly to the bottom of the housing through welding.

New scheme: the positive collector plate is directly welded to the positive column, the positive column is stuck on the opening at the bottom of the shell groove, and there is an insulating seal between them, the battery cell is a full-pole lug structure.

The two ends are connected with the positive and negative collector plates and the pole is electrically connected through the positive collector plate and the battery, the shell and the negative collector plate are electrically connected, the cover plate and the shell are connected by the notch, and the cover plate is etched with explosion-proof lines.


4680 battery brings new opportunities for battery material industry

Previously due to the subsidy decline brought cost reduction demands, safety problems were obvious. The main auxiliary materials to the direction of high energy and high rate of upgrade slowed down, and Tesla 4680 battery is expected to become a new upgrade pusher.

The permeability/dosage of main auxiliary materials such as high nickel cathode, silicon carbon anode, lithium supplement, carbon nanotube, LiFSI, PVDF are expected to increase.

1) High nickel cathode: With high operating voltage and specific capacity, is a potential cathode material for power batteries;

2) Silicon-based carbon anode: As an ideal next generation anode material, the specific capacity of pure silicon is 10 times that of graphite;

3) Lithium supplement: In addition to the low first effect of the silicon carbon anode, the SEI film will “breathe” regeneration during the cycle process, which reduces the cycle life, and the demand for lithium supplement is getting stronger;

4) Carbon nanotubes: Due to the poor conductivity of silicon based anode materials, it is necessary to add carbon nanotubes (CNT) to increase the conductivity between active substances and improve the energy density of the battery;

5) LiFSi: A new type of lithium salt suitable for high-nickel, high-voltage and high-rate batteries;

6) PVDF: Mainly used in the battery in the lithium battery separator and cathode as a binder.

In terms of structural parts, since the Tesla 4680 battery adopts a new configuration design, the manufacturing threshold has been raised, making the structural parts turn to customization, shell+cover plate procurement, the layout is optimized and the value of single products is increased.

In terms of equipment, the amount of laser die-cutting, laser welding and other processes has increased, and the high-precision requirements have increased the value of related equipment. The head battery factory plans new production capacity, and the shell stamping equipment is expected to be replaced by Chinese manufacturing.

In addition, because all lugs are closely arranged, it is difficult to use metal die-cutting, and in some schemes, the width of the lugs changes along the length of the pole piece, so laser die-cutting is more suitable. Laser welding equipment benefits from the Tesla 4680 battery plan, and the major battery factories in the superimposed industry also plan to have production capacity, which is expected to usher in a rapid increase in volume.

Leading 4680 battery companies: CATL, EVE Energy, and other top 10 4680 battery manufactureres.

Suppliers of main materials for 4680 batteries: CNGR (high nickel), Easpring Technology (high nickel), Putailai (silicon carbon), Shanshan (silicon carbon), Dynanonic (lithium supplement), Ke Dali (shell), Cnano Technology (carbon nanotubes), Tinci Materials (LiFSI), Capchem (LiFSI), BRT (high nickel+carbon nanotubes), Fangyuan (high nickel) , Slac (shell), Hymson (laser die-cutting equipment), Uwlaser (laser welding equipment), JDM (stamping equipment).


Difficulties in mass production of 4680 battery

The new structure of the Tesla 4680 battery brings process realization and consistency challenges, affecting the battery yield rate.

Coating: The curved edge of the all-pole lug coating requires higher precision of the device (the blank area of outer ring is getting more and more than the inner ring, and the pole lug length is longer to the outer ring).

Pole lug cutting: Higher process requirements, if the edge is uneven, it will result in a gap in the pole lug fitting.

Laser welding: All-pole lug and collector plate welding, welding points increased (the number of solder joints in Tesla 4680 battery is more than five times higher than that in 21700), easy to create virtual welding or high temperature damage diaphragm.

Kneading: Metal chips are produced.

Liquid injection: It is difficult to inject liquid after all-pole lug covering, which affects continuous production.


The performance advantages of Tesla 4680 battery

Tesla made the design improvement of “large cell+all-pole lug+high nickel and high silicon+CTC” for the Tesla 4680 battery to achieve a number of performance advantages:

1) Long endurance: Tesla 4680 battery energy density increases >20%;

2) Fast charging: The all-pole lug optimizes the thermoelectric performance of the battery and can withstand high rate current above 4C;

3) Low cost: Large battery+high energy density, reducing the cost of single Wh.

In addition, Tesla 4680 battery due to its better thermal safety performance, internal stress distribution uniform advantages, is more suitable for high nickel and high silicon system compared with square batterie. It is expected that low-end cars will be more application of phosphorus square+CTP scheme, high-end cars will be more application of high nickel and high silicon 4680+CTC scheme.

Global leading battery suppliers such as LG, Panasonic, Samsung, CATL, EVE energy, etc., have also followed up the layout of Tesla 4680 battery. The Tesla 4680 battery is expected to usher in an inflection point driven by Tesla and the leading battery manufacturers.


Technology innovation of Tesla 4680 battery

Adopt all-pole lug
● Reduce resistance:
The design of the all-pole lug can reduce the electron flow path and reduce the internal resistance. 21700 battery electrons flow through the entire spanwise length of the wound pole sheet in the collector, the path is about 1000mm, and the corresponding impedance is greater than 20mΩ according to the electrical conductivity of copper.

In the Tesla 4680 battery all-pole cell, the path of electrons flowing through the collector fluid is only the axial length, that is, 80mm, and the corresponding impedance is 2mΩ.

● Reduce heat
In terms of heat production, the heat is reduced as the resistance reducing(the heat of the all-pole lug battery is only 1/5 of the unipole lug). In terms of heat dissipation, a strong thermal conductivity path is formed along the radial direction, and only the cold plate can be arranged at the bottom (the original 21700 is a serpentine tube cooling side wall), which reduces the difficulty of thermal management and energy consumption.

In summary, the loss of electricity and heat energy is small, breaking the constraint that energy and power density can not be increased at the same time, and achieving long battery life and fast charging.


● Simplify the process

The pole plate of 21700/18650 needs to leave a blank area for the pole lug, and the full pole lug can avoid zebra coating and simplify the battery production process.

Adopt high nickel and high silicon

In principle, the 4680 cylindrical battery is only a form of packaging, and there is no limit to the material system. However, from the application aspect, high nickel and high silicon can give play to the advantages of 4680 large cylinder with better thermal performance and uniform internal stress distribution than square battery.

● Energy density

Because the integration efficiency of the cylindrical battery is lower than that of the square battery, that is, to make a pack with the same energy density, the energy density of the cylindrical single must be higher than that of the square. Therefore, to achieve a higher pack energy density, the cylinder naturally requires high nickel.

● High nickel adaptation degree
Cylinder is more suitable for high nickel than square. The core reason is that the square high nickel is the surface contact, and the single battery is large, the heat production in the body is not easy to release, and the thermal runaway design is not easy to control.

On the other hand, the chemical properties of lithium iron are stable, and the requirements for heat dissipation and thermal runaway are lower, so the square CTP is very suitable for the battery of lithium iron system, giving full play to the advantages of high square integration, but the thermal runaway design is difficult. 4680 lithium has lost the advantages of 4680 in passenger cars, and may be applied in the future in two-wheeled vehicles and power tools.

In addition, due to the expansion of the negative electrode after adding silicon, the internal stress dispersion of the cylindrical shape is more uniform than that of the square, which is easy to cause particle breakage under this scheme, affecting the performance and life. Therefore, in order to increase the energy density of the cell, a high-silicon solution with high nickel is selected.

Achieve low cost
● Inactive material cost
Take structural parts as an example, 21700 battery shell + cap 2 RMB, 4680 is currently about 10 RMB, long life M3 needs to use 21700/4680 battery cell 4400/960, the current corresponding to the value of 8800/9600, so the cost of bicycle battery structural parts is basically flat. The price reduction space is huge after the late volume, assuming that the cost can be reduced by 30%, a single structural part can save about 2000 RMB than 21700.

● High energy density

Graphite + high nickel energy density of 283wh/kg (compared to LG 21700 battery which is 247wh/kg), silicon carbon +83 series high nickel energy density of 300wh/kg, 91 series target 350-400Wh/kg.

● Cost savings in the production process

Mainly reflected in the dry electrode technology in the early stage of the production cycle, the positive and negative particles are mixed with polytetrafluoroethylene (PTFE) binder to make it fibrose, and the powder is rolled directly into a film and pressed onto aluminum foil or copper foil to prepare a positive and negative electrode sheet.

In this way, the complicated rolling and drying processes can be omitted, greatly simplifying the production process, improving production efficiency and saving costs.


Current status of 4680 battery industry chain

For Tesla, with the promotion of Tesla 4680 battery, there will need to be two or three foundry factories in China to achieve greater production capacity in the future, and other major battery factories will follow up the layout of Tesla 4680 battery. 2023 is expected to usher in the first year of the outbreak.

Global: Tesla first announced in September 2020 that it would start delivering Model Y with 4680 battery in 2022Q1.

Panasonic plans to start trial production of 4680 batteries in Japan in 2022 H1 and mass production in 2023; LG will expand 4680 battery capacity at the Ochang plant in South Korea and plan to mass produce in 2022-2023; Samsung SDI plans to achieve mass production in 2024, and Israeli company Storedot announced in September 2021 that it successfully produced the first 4680 battery and plans to achieve mass production in 2024.

China: CATL is speeding up the pace of research and development, planning mass production in 2024; Bic exhibited large cylinder products at Shenzhen CIBF in March 2021, and mass production is expected in 2023; EVE Energy put 20GWh large cylinder battery production project into production in 2021 Q4 in Jingmen, and is expected to achieve 4680 battery mass production in 2024.

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