Investigation of Acoustic Attenuation and Resonances in Lithium-Ion Batteries Using Ultrasound Spectroscopy

Ultrasound spectroscopy up to 6 MHz is carried out on a 12 Ah Lithium-ion battery pouch-cell. The analysis revealed that the attenuation behavior can be effectively described as having an absorption component and a resonance component. It was demonstrated that the absorption can be modeled as a second order polynomial. Two distinct resonances were identified at 2.2 MHz and 4.4 MHz. The first of these resonances shows a significant almost linear reduction in magnitude with increasing state of charge. By smartly choosing the ultrasound interrogation frequency to coincide with this resonance, an almost linear increase by a factor of more than five was measured in the signal amplitude between between state of charge levels of 0 and 100. This could provide the basis for a robust and straightforward state of charge determination method. Ultrasound spectroscopy (up to 6 MHz) on a 12 Ah Lithium-ion cell reveals absorption and resonance components of attenuation. Two resonances are identified. The attenuation of the first resonance linearly decreases with state of charge. Matching interrogation frequency to this resonance yields a 5x signal amplitude increase across 0-100 % charge, potentially enabling robust state of charge determination. image