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The Fit LTO cell is physically a flattened roll of long sheets of cathode, anode, and separator media all fully enclosed within a thin aluminum prismatic enclosure. I have a failed cell which I have begun to disassemble in order to study the construction technique. I am devoting no attention to the chemistry of the cells as that has been covered in other scholarly sources. I will add and edit this OP and thread as I learn more.

Most of the cell is visibly hidden by the packaging and stacking of cells. I have separated and exposed the cell at its basic level - a thin prismatic(rectangular) aluminum can.
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This is a picture of the top of the basic cell. The two terminals are obvious, positive red and clear negative near the edges on the top. The rather strange cross hatch shape in the center of the top is what seems to me to be a one time vent for the cell, however I have seen no verification of this fact. I cannot read the QR Code on the top of the cell but will be able to get it read this weekend. It appears that during manufacture the cell is assembled on the top cover, then the entire contents are inserted into the "can."

The next picture shows some of the internal construction detail.
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The bottom of the cell is shown on the right. The active battery material flat roll is clear in this shot. the roll is supported within the aluminum enclosure by a clear plastic frame. At this stage of disassembly, the frame is clearest at the bottom of the cell, where it extends about 25mm into the cell. There is a space in the mid part of the cell bottom where the roll is unsupported. The barely visible feeler gauge on the right is a .025 feeler gauge which fits comfortably into this void. There is a similar space at the top of the cell. The "bottom" as referenced here is the portion of the cell which is open to inspection and visible at the bottom of the packs.

The last picture for today is a closeup of the roll support at a bottom corner. Because the cell enclosure is quite thin, the cell walls have sometimes arrived with minor to moderate damage of the cell enclosure bottoms. This is usually indicated by marks, dents and gashes on the bottom plastic tray of a pack. The damage can be inspected more carefully by peeling back the layer of putty like material under the plastic cover. I have included this picture so that folks can determine which internal parts might be affected by dents in the aluminum case.
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The approximately 25mm part of the plastic frame which support the active battery roll is clearly visible here.

So, that's it for today. I'll be adding additional pictures and information as I dig deeper:)
 

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Hi Jime,
Glad to see this thread. Can I assume that the plastic frame is hard and not compressible? Also, it would be helpful to know the radius of the battery roll at the bottom.
 

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Discussion Starter #3
Yes, the clear plastic inner frame is of hard plastic.

I haven't taken the battery roll out of the can yet, but the roll fully fills frame fully fill the rectangular cell. The frame is about .025 thick.

I won't have much time to continue the autopsy until sometime next week when my latest mounting frame goes to the machine shop for welding.

You can calculate the radius easily from the outside dimensions of the can - not handy at the moment. Just subtract 2 x .020(can metal thickness) and 2 x .025(frame thickness) from the can thickness to find diameter of the roll at the bottom.

Radius = Diameter/2. (That's a joke. I know you know :D)
 

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Got badly sidetracked. Mommy fell and broke a hip. In rehab full time so I now have a bit more time to do stuff. Should get back to this sometime this week.
 

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Discussion Starter #5 (Edited)
More pictures of internals.
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This is a picture of the cell internals. As I suspected earlier, the cell seems to have been assembled onto the top cap, then the cell internals were inserted into the outer can. :)

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These are the two internal L brackets which are fitted to the edges of the roll of active cell material.

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This shows some detail on internals. It can be seen that the cell consists of a long roll of active plates which has been rolled into a flatten mass. At this point I'm a bit confused. There are two clamps on edges of the roll(positive side shown). The internal bus bar is also U shaped. It looks a bit like there may be two batteries in parallel OR they may have done this handle the peak current with the rather small bus bar.

88531

After peeling of the single blue "cover" layer one finds this light blue very thin film layer which has the consistency of a very thin film tape like tydex, but is v ery easily torn. The next layer is the dark grey, which might have been an electrolyte paste before the volatile elements out-gassed. Scraping away a bit of this, one finds a third layer which looks like a very thin aluminum foil. I will need to somehow remove the edge clamps before I can verify that the light blue and the aluminum are the anode and cathode of the cell.

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This last photo shows the one-time vent forced open. I believe that opening of this vent is probably the explanation for the few observations of the sickeningly sweet smell that some have observed.

I'll probably try some more delicate surgery to release the edge clamps and determine which material serves what function.

BTW, mommy considerably improved in rehab:)
 

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Amazing what it takes to build a cell / pack. I don't recognize anything there. Is that a single cell?
 

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Amazing what it takes to build a cell / pack. I don't recognize anything there. Is that a single cell?
Yep, this the entire contents of a single cell. As I said, the cell is built upon the cell top and then inserted into the outer aluminum can.

You don't recognize any of it because almost all of this is hidden from view when the sub-pack is assembled.
 
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