Meaning
Progressive mechanical degradation of an active material layer under cyclic interfacial shear stresses leads to micro-cracking and eventual delamination from a current collector foil. High-rate calendering and mechanical flexure during cell assembly subject coating shear fatigue limits to repeated stress cycles that weaken interfacial adhesion over time. Slurry formulations with inadequate binder crosslinking concentration display low resistance to shear failure, causing active material particles to detach from copper or aluminum substrates during fast charging cycles.
Measurement of this failure mode defines the mechanical lifespan boundary of coated battery electrodes.
Stress Mechanism
Alternating shear forces arise during electrode winding and volumetric expansion during lithiation cycles. Dynamic expansion of silicon-graphite blended anodes creates intense cyclic stress at the current collector interface, initiating micro-fractures within the binder network. Cumulative mechanical work degrades the polymeric matrix, transforming elastic deformation into permanent micro-structural displacement.
Delaminated regions increase local contact resistance and create isolated pockets of inactive material.
Testing Protocol
Mechanical fatigue testing applies cyclic lateral displacement to coated electrode strips under fixed compression loads. Dynamic mechanical analyzers measure loss modulus shifts to record the onset of coating shear fatigue micro-cracking prior to visible surface peeling. Standard test runs evaluate sample endurance across thousands of load cycles at controlled humidity levels.
Results guide polymer binder formulation adjustments for high-capacity silicon anode coatings.
Adhesion Limit
Interfacial bonding strength dictates the minimum threshold required to prevent delamination during cell assembly. Exceeding the coating shear fatigue limit causes localized foil exposure, increasing internal impedance and risking short circuit formation.
