Here is a very interesting video of a Tesla 4680-type cylindrical battery cell teardown, presented by The Limiting Factor, in partnership with a team from UC San Diego.
As we know, the 4680-type (46 mm in diameter and 80 mm tall) is the latest and the biggest cylindrical cell for Tesla EVs (see more about Tesla batteries here), currently used in the Made-in-Texas (MIT) Tesla Model Y.
According to the video, this particular cell comes from Tesla's Kato Road pilot facility in Fremont, California.
The video is essentially four hours of work in the lab, compressed to about one hour (see timestamps down below). A second part is expected to be released in the near term with the data/characterization).
The opening of the steel case happened to be quite difficult. The case appears to be some kind of stainless steel and surprisingly thick - potentially because the cells are envisioned for structural battery packs (glued together and ready to carry external forces).
On the bottom, there is a copper "flower", connected to the anode in a tabless design. The bottom metal part is electrically isolated, but the side case is not. Similarly, on the top, there is an aluminum "flower" for the cathode (electrically connected to the top center part).
To better understand what is the tabless design, it's worth checking out the EEVblog's video from 2020 (3:48 - 14:00), which explains the difference and explains how the "flower" or "shingle spiral approach" works. EEVblog notes how it reduces the length of the electrical circuit, which means lower resistance and higher power capability.
Other than that, the jelly roll of the active material (cathode, separator and anode) appears to be similar to conventional solutions.
It will be interesting to see the characterization of the cell, which maybe will reveal the battery chemistry Tesla uses in in-house produced 4680-type cells.
Timestamps:
00:00 Introduction
03:02 Prep
04:19 Voltage Check (OCV)
05:17 Creating a Cut
07:04 Comments on Toughness
07:50 Prying Access to the Copper/Anode
13:17 Copper/Anode Finally Opens
16:31 Removing the Tabless Cover (Flower/Hubcap thing)
19:21 Tabless Electrode Exposed (Copper)
23:33 Cutting the Side Wall
27:57 Jelly Roll Removed and Tabless Electrode (Aluminum)
30:15 Removing Tape Wrap
31:45 No Tabless on Outer Wraps
33:45 Cleaning Up the Glovebox and Collecting Electrolyte Crystals
36:49 A Quick Look at the Aluminum ‘Flower’
37:48 Collecting Electrolyte, Cleaning, Unwrapping Jelly Roll
41:34 Notes on the Cathode
42:30 Folding Cathode
42:56 More Notes on Cathode
43:48 Folding and Measuring Anode
47:44 Cathode and Anode Lengths
47:59 Measuring Width (roughly 70mm)
49:25 Decision to Cut a Piece and Measure Outside Glovebox
49:31 Cutting a Piece
50:42 Discussion on Length and Cutting Coin Cells
52:33 Closing Notes on Day 1
53:37 Day 2 Start – General Discussion About Structure
57:43 Cutting Open the Sidewall to Access the Aluminum Top
01:01:17 Discussion of the Button, Plastic, Aluminum ‘Flower’
01:02:37 Attempting to Deconstruct Aluminum Top Further
01:04:34 More Discussion of the Button, Plastic, Aluminum ‘Flower’
01:06:45 Cutting a Piece of the Sidewall
01:07:29 Sidewall Thickness
01:08:24 Measuring the Thickness of Other Pieces
01:10:40 Comparing the Aluminum and Copper ‘Flower’
01:11:29 The Cell Can is Structural
01:12:19 When Can We Expect Results?
