Ionic Strength‐Mediated pH‐Responsive Crystalline Domain Formation Drives Enhanced Toughness in Protein Hydrogel Electrolytes

Abstract Pure protein‐based electrolyte gels have garnered significant attention due to their biosafety, degradability, and environmental sustainability. Nevertheless, their high mechanical stabilities and ionic conductivities are difficult to reconcile, especially in the presence of chaotropic anions. Herein, this study presents a facile ionic strength‐mediated pH‐responsive crystallization strategy to fabricate a tough pure protein‐based gel electrolyte containing chaotropic Cl − anions. By leveraging the electrostatic shielding effect of NaCl to promote phytic acid dissociation, a highly acidic environment is constructed to trigger protein precipitation and crystalline domain formation, thereby significantly enhancing the mechanical properties of the gel. The optimized gel exhibits a tensile strength of 0.14 MPa and a tensile strain of 1039% in the presence of NaCl as high as 5 m . Owing to the efficient coordination of Na⁺/Cl − with amide groups in the protein backbone, the gel also demonstrates excellent ionic conductivity and superior electrochemical performance, including a high specific capacitance (51 F g −1 ) and a coulombic efficiency of 99.4% after 1 00 000 cycles. Furthermore, the gel retains its inherent biodegradability, enabling complete and harmless assimilation into the environment after its service life. These collective properties position it as a highly promising electrolyte material for next‐generation flexible energy storage devices.