A bit of background. This cell is one of the green-wrapped Sony 2200mAh cells from the 12-cell HP laptop packs. When cutting apart the cluster endplates the sharp edge pierced the insulator at the + end and shorted the cap with the body of the cell. I cleaned as much of the burned plastic and possible weld boogers off of it as I could, but even under a magnifying glass I cannot tell where the - case ends and the + cap begins. The cell has since been carefully cleaned and re-wrapped. The shorting was momentary, and the cell as since charged, partially discharged, and been charged again, and held 4.15v for…about a couple weeks now I’d guess (my i4 only goes to 4.15).
I took it out of the box I keep my pack-pulls in and noticed that the top rim above the crimp is 75% circumfrentially covered in some black goo. It has the appearance as if someone poured a gel-pen’s ink onto the table, rolled the rim in it, and then put on the shrink-tube. I encountered slight smears of this substance earlier soon after the short but I had in fact been playing with gel-pens earlier and thought it was transfer. At no point did I observe foul or sweet odors that I’ve read are associated with a leaking or compromised li-ion cell. The cell was cleaned before the shrink wrap was applied, so this is not external contamination.
I suspect the advice given will be to have the cell recycled, but does anyone know what this substance is?