In situ detection of lithium-ion batteries by ultrasonic technologies

Overcharging is one of the most frequent and dangerous hazards in lithium-ion batteries, which not only increases the risk of battery failure but also causes thermal runaway and catastrophic outcomes. In this work, we combine the A-scan and 2D/3D Total Focusing Method (TFM) ultrasonic detecting technologies to in situ monitor and image the battery's abnormal behavior under overcharging. The ultrasound wave behavior during the charge/discharge process at various current densities and cut-off voltages is demonstrated first to obtain a general comprehension of its relations to the lithiation/de-lithiation, volume changes, concentration polarization, and temperature elevation process. Moreover, the early-warning characteristic of ultrasonic detecting has been proven in overcharging. The onset and location of side reactions can be precisely and facilely detected by ultrasonic detecting technologies as early as 102% SoC after the overcharging begins, and various overcharged states can be differentiated with an accuracy of 0.4% SoC. The astonishing precision of ultrasonic detecting technologies allows a timely remedy to be applied to batteries, thus elongating batteries' lifespan. In conclusion, the ultrasonic detecting technique is excellent at not only accurately detecting the battery state but also acting as an alarm for latent danger.