Ultrasound-Based Battery State-of-Charge Monitoring and Health Evaluation Using High Directivity MEMS Transducer

The development of lithium-ion batteries necessitates effective monitoring methods for accurate battery state-of-health (SOH) assessment and safety assurance. Traditional battery monitoring approaches, which rely on electrical properties and algorithmic analysis, are limited in detecting battery instability and early-stage degradation. Ultrasound technology offers a non-destructive and real-time method for evaluating lithium-ion batteries. However, it faces challenges related to non-integrability, large volume, and poor coupling efficiency. Here, we present a compact 300 kHz piezoelectric micromachined ultrasound transducer (PMUT) array with 7° high-directivity, specifically designed for battery monitoring. The effect of temperature on ultrasound detection was analyzed, showing a 61.5% decrease in maximum ultrasonic signal amplitude. The maximum absolute correlation coefficient between the ultrasound signal and battery status is ~0.8, which has the potential to be further improved by the multi-point ultrasonic detection method. The measured SOH of the battery drops from 89% to 76% as the temperature decreases, which demonstrates the feasibility of battery status monitoring in low-temperature environments. Compared to previous work, the proposed method demonstrated a promising solution of a small-footprint device for accurate low-temperature battery status monitoring.