The M50lt 21700 cylindrical cell (21-mm diameter and 70-mm length) chosen as an initial ECN target is the LG-INR21700-M50LT. Batches of batteries from different lots have been purchased and are available for ECN research upon request. Scans of the internal geometry of the injector have been performed by Sandia (credit Bernice Mills) using x-ray computed tomography imaging, with slides presented at ECN9.13 and 9.18 showing details. M50LT cells have also been opened and inspected in the literature and cell material inventories for mass and percentage of components of from similar M50 cells are reported. The cathode is NMC811, the anode is graphite with 1% silicon, and the cell mass is 5.6% electrolyte (electrolyte mass is 78% dimethyl carbonate). The overall structure of the jelly roll, casing, voids, and aluminum cathode tab midway through the jelly roll is shown at the right. Details of the Charge Interrupt Device (CID) and burst-disk geometry and venting operation at the top of the cell are described in the ECN9.18 slides.

Feature of the internal geometry are used to produce STL surface files and other computational mesh setups for analysis of thermal runaway. The table below includes 2D axis-symmetric options (that neglect asymmetries such as the cathode tab) for less-expensive calculations. These STL files have simplified geometries at the CID/burst disk. Note that there are substantial voids at the center, top, and bottom of the jelly roll, which will affect conductivity and heat flow to the battery. Also, the jelly roll is encapsulated by the plastic separator at the interface with the stainless steel casing, which will increase contact resistance. 

File Description Credit
M50LT 2D STL without heater 2D “thin STL” of half battery without brass heater  Steven Luna, Lyle Pickett (Sandia)
M50LT 2D STL with heater 2D “thin STL” of half battery with brass heater  Steven Luna, Lyle Pickett (Sandia)
jellyroll, void, casing, heater Various STL elements of 2D assembly, each as a separate STL Lyle Pickett (Sandia)
coming 3D STL model of battery, including aluminum cathode tab Steven Luna, Lyle Pickett (Sandia)
CVG zip file CONVERGE 4.1 case with regions identified for 1.5C/min ramp Martin Rieth (Sandia), Koby Rouviere (U Cent. FL), Kislaya Srivastava (Convergent Science)
M50LT SLDPRT SolidWorks file of the battery, heater, and simplified internal features  Andy Wang (Sandia)

Side-view of a “thin” STL, with symmetry axis at the left. This is one-half of the cell, for 2D axis-symmetric cylindrical-coordinate simulations: M50lthalf