Tough Interfacial Adhesion Enabled Extremely Durable Flexible Supercapacitors

The interfacial void and delamination between the hydrogel electrolyte and flexible electrode caused by the inconformal contact and weak adhesion lead to serious performance degradation of solid-state-sandwiched supercapacitors (SCs) upon repetitive deformation. Herein, we propose a hydrogel polymer electrolyte (HPE) engineering strategy for enhancing the interfacial adhesion (Γ) to achieve extremely durable SCs via the soft, tough, and self-adhesive HPE. Using a self-cross-linked poly(N-hydroxyethyl acrylamide)/H₃PO₄ (PHEAA/H₃PO₄) HPE as the model, the interfacial adhesion between HPE and polyaniline (PANI)-modified carbon cloth (CC) electrode (CC/PANI) reaches up to 556 J/m², leading to excellent durability of electrochemical performance under long-term repetitive deformations. The as-assembled sandwiched SC retains 94.14 and 93.62% of initial capacitance after 180° bending and twisting for 100,000 cycles, respectively. Furthermore, benefiting from the addition of H₃PO₄, the flexible sandwiched SC displays excellent tolerance to low temperatures and delivers a capacitance retention of 98.03% after 180° bending for 10,000 cycles at -20 °C. This work highlights the importance of interfacial adhesion engineering for the design of extremely deformation-tolerable SCs.