Lewis acid-base mediated MOF-polymer hydrogel electrolyte for oriented ion conduction and textured Zn (002) deposition

Abstract

Hydrogel electrolytes offer inherent flexibility and safety advantages for Zn-ion batteries, yet their practical implementation remains hindered by insufficient Zn²⁺ mobility and unstable anode/electrolyte interfaces. This work leverages molecularly engineered Lewis acid-base interactions to integrate rigid metal-organic frameworks into flexible polymer networks, providing fundamental insights into Zn²⁺ transport mechanisms and deposition control. By incorporating zeolitic imidazolate framework-8 (ZIF-8) into a polyacrylamide (PAM) matrix, we fabricate a composite hydrogel electrolyte (PAM@ZIF-8) featuring precisely oriented ion-conduction pathways. The molecular-level design of complementary Lewis acid-base sites between ZIF-8 and PAM optimizes amide group interactions with mobile Zn²⁺ ions, enabling a rapid ion-hopping mechanism that yields a high Zn²⁺ transference number of 0.73. Additionally, the CN moieties in ZIF-8 serve as adaptive traps for SO₄²⁻ and H₂O, stabilizing mass transfer. Crucially, the interfacial chemistry of ZIF-8 steers crystallographic orientation via preferential adsorption onto Zn (002) facets, directing facet-specific kinetics to achieve dominant (002)-textured deposition. Consequently, PAM@ZIF-8 electrolyte enables ultra-stable Zn plating/stripping for >6500 h in symmetric cells (1 mA cm⁻²/1 mAh cm⁻²). Full Zn-ion batteries paired with a V₂O₅-based cathode exhibit exceptional long-term cyclability, retaining 95.0 % capacity after 3000 cycles at 5 A g⁻¹.