Nonlinear Acoustic Shear Wave Detection of Zero Gap Kissing Bonds in Encapsulated Packs
Nonlinear acoustic shear wave harmonic detection resolves zero gap kissing bonds in encapsulated battery packs by measuring contact acoustic nonlinearity.
Micro Clapping
Meaning
A localized, high-frequency physical opening and closing of microscopic contact interfaces under the influence of acoustic waves causes non-linear ultrasonic behavior in damaged materials. This micro clapping occurs when a high-intensity ultrasonic signal passes through a battery electrode that has suffered micro-cracking or delamination. The acoustic pressure alternately compresses the crack shut and pulls it open, generating higher harmonics of the original signal frequency.
Nonlinear Signal
Conventional ultrasonic testing measures the energy of the transmitted or reflected wave at the same frequency that was injected. When a damaged region exhibits this non-linear interaction, the output signal contains frequencies that are multiples of the input frequency. These harmonic signals provide a clear indication of structural degradation even when the cracks are too small to block the primary wave.
High sensitivity to these harmonics makes it possible to detect early-stage mechanical fatigue in lithium-ion battery electrodes.
Diagnostic Application
Researchers and quality control engineers use this non-linear response to evaluate the cohesion between the active material and the current collector. During cycle testing, the repeated expansion and contraction of silicon or nickel-rich cathodes can cause the composite layer to detach. This physical separation results in a rise in internal resistance and a loss of capacity.
Detecting this detachment before complete failure occurs helps developers optimize binder materials and electrode density.
Sourcing Relevance
Procurement managers use non-linear ultrasonic data to evaluate the structural integrity of cells from new suppliers during the qualification phase. Cells that show signs of early mechanical degradation are rejected to avoid field failures. This testing reduces the risk of investing in unproven battery technologies.