# Non-Destructive Thickness Measurement of Energy Storage Electrodes via Terahertz Technology

## TL;DR

This paper introduces a non-destructive method using terahertz technology to accurately measure the thickness of battery electrode coatings, improving battery performance and manufacturing quality control.

## Contribution

The study introduces a hybrid signal processing algorithm and multi-peak amplitude analysis for improved terahertz-based thickness measurement accuracy.

## Key findings

- The method achieves a 1% error rate in determining material refractive index.
- The hybrid algorithm improves accuracy by 2.13% and extends the measurement range by 17.62%.
- Real-time online measurement is enabled under atmospheric conditions using the time-of-flight method.

## Abstract

Precision thickness control in new energy electrode coatings is a critical determinant of battery performance characteristics. This study presents a non-destructive inspection methodology employing terahertz time-domain spectroscopy (THz-TDS) to achieve high-precision coating thickness measurement in lithium iron phosphate (LFP) battery manufacturing. Industrial THz-TDS systems mostly adopt fixed threshold filtering or Fourier filtering, making it disssssfficult to balance noise suppression and signal fidelity. The developed approach integrates three key technological advancements. Firstly, the refractive index of the material is determined through multi-peak amplitude analysis, achieving an error rate control within 1%. Secondly, a hybrid signal processing algorithm is applied, combining an optimized Savitzky–Golay filter for high-frequency noise suppression with an enhanced sinc function wavelet threshold technique for signal fidelity improvement. Thirdly, the time-of-flight method enables real-time online measurement of coating thickness under atmospheric conditions. Experimental validation demonstrates effective thickness measurement across a 35–425 μm range, achieving a 17.62% range extension and a 2.13% improvement in accuracy compared to conventional non-filtered methods. The integrated system offers a robust quality control solution for next-generation battery production lines.