Tesla 4680 Cell

The Tesla 4680 cell has intrigued ever since it was announced. A cylindrical cell that is 46mm in diameter and 80mm high.

Estimated Specifications:

  • Cell format: 4680
    • Diameter: 46mm +/-
    • Height: 80mm +/-
    • Volume: 0.1330 litres (outer volume)
    • Cell case
      • stamped and drawn nickel plated steel or stainless [3]
      • 0.5 to 0.6mm thick
  • Capacity: 26.5Ah (estimate based on 21700 5Ah volumetric energy density)
    • Cathode:NMC811
      • solvent based slurry and application
      • electrode thickness ~85µm [2]
      • aluminium current collector thickness 9 to 10µm [2]
      • aluminium “flower” end disc thickness 400µm [3]
    • Anode
      • carbon, no silicon [2]
      • dry based electrode [2]
      • copper “flower” end disc thickness 260µm [3]
  • Nominal Voltage: 3.7V

The assumption is that Panasonic / Tesla have initially used the same fundamental chemistry in this cell as the 21700 or even stepped back to the previous one. This would be a sensible approach as the format change is significant and is likely to bring a number of issues. Hence you would want to stabilise the chemistry and reduce the swelling associated with silicon in the anode.

  • Nominal Energy: 98Wh
    • Roadmap:
      • 108Wh in 2023
      • 118Wh in 2024
  • Mass: 0.355kg
  • Metrics:
    • Cell volumetric energy density = 737 Wh/litre
Tesla 4680 cell

What you immediately notice with this cell is that the crimped closure is on the negative, bottom, of the cell (the top of the image on the left). This is in contrast to the 18650 and 21700 cells where the cell is crimped closed with an isolating and sealing gasket around the +ve, top end of the cell.

This means that the positive button on the top of the cell is pre-installed into the empty can shell and is isolated from the can.

Online recording of a discussion around the manufacturing process for the 4680 cell.

The 4680 manufacturing process appears to be:

  1. roll the anode, cathode and separator (appears they cut into the tabs ready to fold at this point)
  2. fold the tabs over – this must result in wrinkles on the edge of the active materials
  3. laser weld the cathode and anode discs to the jelly roll
  4. fit the positive button into the can with isolator (this might arrive pre-assembled)
  5. push the jelly roll into the can and weld the cathode disc to the underside of the +ve button though the hole in the anode disc and centre of the jelly roll (very similar to the current 18650/21700 process for the anode connection to the bottom of the can)
  6. weld the anode disc around the edge to the inside of the can
  7. fit the can closing disc and crimp this into the can (this step has been changed apparently as the crimp was leaking)
  8. fill with electrolyte through the hole in the centre of the closing disc
  9. close/weld the hole in the closing disc

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Based on this we have constructed a schematic that sows the cross-section through this cell.

Tesla 4680

It appears that this is an old design. The following are a couple of issues described online:

  1. The can closing process is different. The design in the picture shows a weakness, which makes it difficult to get it work, in the closing process since is missing the gasket between lid and can so even with grooving + crimping process you cannot ensure hermetically sealing, and you waste too much space in the can.
  2. Even the cathode disc design is different from the picture above. No reason to do it like that, you loss energy density (no space optimization).

It appears that this cell is designed to rupture or un-crimp the bottom disc in the event of the cell going over pressure. The next video shows the cells being assembled into a battery pack that appears to show serpentine side cooling. This would make sense if the bottom of the cell is designed to be the venting path.

Tabbed vs Tabless

The tabless jelly roll significantly improves the electrical and thermal connections. Tranter et al [1] have analysed this design and looked at the electrochemical and thermal behaviour.

The new design is found to mitigate the ohmic losses experienced around the “jelly-roll” current collectors which are significant for the traditional tabbed case, thus leading to higher efficiency and capacity and reduced heat production.

T. G. Tranter, R. Timms, P. R. Shearing and D. J. L. Brett, “Communication—Prediction of Thermal Issues for Larger Format 4680 Cylindrical Cells and Their Mitigation with Enhanced Current Collection“, Journal of The Electrochemical Society, Volume 167, Number 16

Safety

  • Cell venting
    • appears to be from the bottom negative end
  • Cell fusing
    • no internal fuse

Other Manufacturers

There are a lot of other companies jumping on the 46mm diameter cylindrical cell format:

  • BAK
  • CATL
  • EVE
  • Gotion
  • LG Chem
  • Lishen
  • Panasonic
  • Samsung
  • SVOLT

References

  1. Panasonic GREEN IMPACT – New Environmental Concept for a Sustainable Future
  2. Tesla 4680 Teardown: Specs Revealed! (Part 2) – The Limiting Factor
  3. Part 1: Tesla 4680 Teardown // Cell Disassembly // 4 hours in 1 hour – The Limiting Factor
  4. T. G. Tranter, R. Timms, P. R. Shearing and D. J. L. Brett, “Communication—Prediction of Thermal Issues for Larger Format 4680 Cylindrical Cells and Their Mitigation with Enhanced Current Collection“, Journal of The Electrochemical Society, Volume 167, Number 16
  5. Not only tesla 4680 battery, which battery manufacturers are in the layout of 4680, TycoRun Energy

Note: we will update this page as more data becomes available.


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