Monitoring the internal structural evolution and gas generation in lithium-ion batteries is critical for effective battery management; however, conventional electrical and thermal sensing techniques lack the sensitivity to capture these dynamic changes accurately. To address this limitation, we apply ultrasonic diagnostic techniques—specifically A-scan and C-scan modalities—to characterize the acoustic responses of pouch-type LFP batteries subjected to a range of current densities (0.5C–5C) and overcharge conditions defined by cutoff voltage and SOC. Our findings show that ultrasonic signals are highly sensitive to concentration polarization and electrode lithiation processes occurring during charge–discharge cycles. At elevated current densities (>2C), an imbalance in the Li+ intercalation/deintercalation process occurs. Overcharge tests reveal that 4.2 V can serve as the threshold voltage for early warning during ultrasonic testing of LFP batteries When SOC exceeds 110%, internal gas generation and mechanical degradation significantly accelerate and become irreversible.
Wang et al. (Wed,) studied this question.