Rejuvenation of Mechanical Fatigue Resistance in Two-dimensional Ferroelectric CuInP2S6 by Reversing Ionic Motion

Two-dimensional (2D) ferroelectrics promise mechanically flexible, multifunctional electronics, yet their long-term mechanical reliability remains poorly defined. Here we scrutinize the ionic van der Waals (vdW) ferroelectric CuInP ₂ S ₆ (CIPS) via atomic force microscopy-based fatigue testing and demonstrate the unprecedented fatigue performance of CIPS that survives > 10 ⁷ cycles at stresses approaching 7 GPa, outperforming the fatigue tolerance of conventional ferroelectric counterparts. This endurance is governed by stress induced flexoelectric fields that drive Cu ⁺ ion migration, forming reversible protrusions. Crucially, the disordered lattice can be repaired to restore mechanical robustness through electric-field controlled ionic motion and extend the fatigue life by a further order of magnitude, establishing an electromechanically switchable self-rejuvenation protocol. Our findings position ion-migration dynamics as a pivotal lever for fatigue engineering in ionic vdW crystals and outline design principles for durable, reconfigurable 2D electromechanical systems.