Method group NG-PM
Post-mortem
A cell that lost 30 % of its capacity lost it somewhere. Teardown is the only method we offer that answers where, and it is destructive, irreversible and unrepeatable — so the order of operations matters more here than anywhere else in the laboratory.
Stages 1 and 2 happen in the open laboratory. From stage 3 onward the cell is inside an argon glove box held below 1 ppm water and 1 ppm oxygen; samples that leave it for diffraction travel in a sealed holder with a polymer window.
Teardown with optical documentation
Seven working days for a single cell, including the report. The deliverable is 60–90 calibrated photographs, a dimensional record of every layer, and a written description of what was found.
- Incoming state: mass to 0.01 g, open-circuit voltage, case dimensions, visible deformation, any smell noted at opening.
- Safe discharge at C/50 to the lower voltage limit, then a 24-hour rest and a second voltage reading. A cell that recovers more than 150 mV during that rest is flagged, because it usually means an internal disconnection rather than depletion.
- Layer-by-layer separation with each layer photographed against a calibration target, so that length measurements in the photographs are usable later.
- Coating thickness at nine points per electrode with a micrometer, reported as mean and range.
- Separator inspected under reflected light for plating marks, blocked pores and perforation.
Teardown with diffraction and micro-CT
Three weeks. Adds three measurements that answer different questions, and they are ordered so that each one does not destroy the next.
- Electrolyte sampling
- 50 µL drawn from the separator before any rinsing, sealed and frozen at −20 °C. We preserve and ship it; the chemistry is done by an analytical laboratory you nominate
- Powder diffraction
- Both coatings, scraped and sealed under argon. Phase identification and lattice parameters; quantitative phase fractions only when the pattern supports them
- Micro-CT
- Full stack at 9 µm voxel size on a cell of up to 21 mm diameter, run before disassembly when the question concerns winding geometry or gas pockets
When micro-CT is ordered it moves ahead of stage 3, since opening the cell destroys exactly the geometry it is there to record. We will tell you this when quoting, but it is worth knowing before the cell is shipped: scanning first adds four days.
What a post-mortem settles, and what it does not
Usually answerable. Whether lithium plated on the anode and over what fraction of its area. Whether the separator was mechanically damaged. Whether the coating delaminated from its current collector. Whether electrolyte was consumed to dryness. Whether the winding was displaced. Whether one jellyroll section aged differently from the rest. Whether a tab weld failed.
Rarely answerable. The exact event sequence of a thermal failure, once the evidence has burned. Whether a contaminant was present in the original material or entered during assembly. Which of two concurrent degradation paths contributed more, when both leave the same visible trace. The cause of a fault that occurred in one cell out of a thousand, from that one cell alone.
We write the second list into every teardown quotation. A post-mortem on a single field return frequently produces a credible story and no proof, and a client who was told otherwise at the quotation stage has reason to be annoyed at the report stage.
Cells must arrive below 30 % state of charge and the packing list must state the measured voltage. We cannot discharge a cell that we are not allowed to transport.
- Cells that have vented are accepted only after a written description reaches us first, and only in a sealed steel container with a non-combustible absorbent.
- Swollen pouch cells are accepted; swollen cells with a leaking seam are not.
- We do not accept cells that were involved in a fire, nor cells recovered from water.
- Nothing above 20 Ah, in any format. The glove box antechamber sets that limit, not the method.
Shipping rules, labelling and the packing list template are on the samples page. Retention after teardown is covered under retention and disposal: disassembled material cannot be returned, and what remains is held for 90 days.