Evaluating the Manufacturing Quality of Lithium Ion Pouch Batteries

Lithium-ion batteries must undergo a series of quality control tests before being approved for sale. In this study, quality control tests were carried out on two types of lithium-ion pouch batteries, here denoted as type A (with stacked electrode configuration) and type B (with a jelly-roll arrangement) to assess the effectiveness of the tests. Electrochemical tests, which included capacity and impedance measurements, found that both types of batteries met the specifications. However, computed tomography (CT) scan, disassembly, and material characterization revealed quality concerns in battery assembly and material composition. Results showed that, for an A cell, cathode extended past anode at the top and bottom of the roll, and a CT scan revealed inhomogeneities in the electrode near the corners. Similarly, analysis of a B cell revealed gaps in the winding structure and cathode material discrepancies. More specifically, the lithium nickel manganese cobalt oxide (NMC) material specified by the battery manufacturer turned out to be lithium cobalt oxide (LCO). The findings indicate that systematic quality control tests are needed to properly identify defects in batteries before they are used in products.