X-ray radiography instrument design for internal defect detection in lithium-ion battery modules for electric wheelchairs

Lithium-ion batteries (LIBs) are widely used in transportation and energy-storage system; however, their increasing deployment raises concerns about thermal runaway caused by internal defects. The aim of the current study is to optimize a radiography instrument to detect internal defects in LIB at the module level. Using Monte Carlo simulation, a commercial cylindrical 18650 LIB module and a CsI(Tl) detector were modeled. To enhance the performance of the radiography instrument, parameters such as X-ray energy, filter material and thickness, pixel size, and magnification were optimized. Quantitative metrics, including signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and detectability index, were used to evaluate image quality. Optimal conditions were determined to be 150 keV X-ray energy, 1.6-mm Sn filtration, 85 μm pixel size, and 2.1 magnification. Under these conditions, crack and delamination defects were distinguishable at sizes of 0.18 and 6.6 mm, respectively. Future work involves fabricating and experimentally validating the prototype instrument under actual LIB inspection condition.