Thickness Measurement of Graphite Coating on Lithium Battery Anode Film by Scanning Acoustic Microscope With Resolution Enhancement Method

Lithium battery as environmentally friendly and low-carbon energy storage has the largest number of applications. The control of the thickness of the graphite coating of anode film is very important and directly determines the capacity, charge and discharge speed, and cycle life of the lithium battery. However, due to the particularity of its structure and materials of lithium battery anode film, there has been a lack of practical thickness measurement instrument and methods. In this article, the scanning acoustic microscope (SAM) has been developed to acquire echo signals during rolling. The resolution enhancement method is proposed to improve the time resolution of the acoustic scanning microscope system by autoregressive (AR) spectrum extrapolation based on the deconvolution method and wavelet analysis. Compared with the existing instruments and methods, the acoustic scanning microscope with resolution enhancement method can measure the thickness of the graphite layer at any point from the center to the edge and can also provide B-scan imaging of the anode film during rolling. The experimental results show that this method can overcome the resolution limitation of the SAM and provide super-resolution thickness measurement for anode film. The range of thickness measurement for graphite coating on the anode can cover as thin as
$30 \mu \text{m}$
. In this article, the measurement of anode film has an important guiding significance for the subsequent research on the safety of lithium battery, so as to effectively improve production efficiency and benefit.