A model-informed analysis of battery electrodes using non-contact air-coupled ultrasound

Non-destructive, in-line battery electrode metrology techniques are critical for reducing material waste, limiting equipment downtime, and improving production yields. This study demonstrates non-contact, air-coupled ultrasound as a technique for evaluating battery electrode films. First, an analytical model was derived from fundamental acoustic wave propagation principles to determine acoustic density. Acoustic density maps of electrode films revealed features that are not visually apparent, attributed to mass gradients. The technique was used to evaluate several applications, such as the impact of calendering and the effect of metal impurities on acoustic density. In all applications, quantitative and statistically significant analyses demonstrated the technique's capabilities for characterizing inhomogeneities within electrode films in a non-contact and non-invasive manner.