High-resolution x-ray imaging under low-voltage conditions is essential for nondestructive evaluation of lithium-ion batteries, where microscale internal defects critically affect safety and long-term performance. However, many previously reported electron emission sources exhibit limitations in beam confinement, particularly under low-voltage or high-current operating conditions, which can restrict imaging resolution and practical applicability. To address these challenges, a newly optimized single-island C-beam x-ray source based on a carbon nanotube (CNT) cold-cathode field emitter is proposed for low-voltage, high-resolution battery inspection. The electron source was optimized through improved electrode geometry and electrostatic focusing, resulting in enhanced beam convergence and reduced focal spot size. Electrical characterization demonstrated reliable operation, delivering a maximum emission current of 1.15 mA in a diode mode and a stable anode current of 0.42 mA in a triode mode. These improvements enabled the formation of a tightly confined focal spot of approximately 32 μm at an anode voltage of 65 kV. Imaging performance was quantitatively validated using line-pair phantoms, confirming a practical spatial resolution of 38.5 μm with contrast-to-noise ratio values ranging from 1.6 to 5.47 under low-dose conditions. The optimized system further achieved high-throughput capability, supporting inspection rates of 300–500 cylindrical cells/min, surpassing conventional low-voltage commercial x-ray systems. The proposed CNT-based C-beam source demonstrates a compact, energy-efficient, and scalable solution for rapid, low-dose, and high-fidelity nondestructive inspection of advanced energy storage devices.
Patil et al. (Tue,) studied this question.