Enhancing Zinc-Ion-Transport Kinetics in Solid-State Zinc Batteries via an Internal/Surface Dual Acceleration Strategy

Solid polymer electrolytes (SPEs) hold substantial potential for enabling highly flexible and stable zinc-ion batteries (ZIBs) due to their nearly anhydrous nature. However, the development of SPEs is still hindered by their poor zinc-ion-transport kinetics. Herein, utilizing CALF-20 as both a filler and a functional coating, a bilayer solid-state electrolyte (BSSE) was designed. On the one hand, the intermediate CALF-20 filled poly(ethylene oxide) hybrid gel demonstrates strong interaction with CF₃SO₃^- anions, thus promoting Zn²⁺ dissociation and transmission. On the other hand, the outer single CALF-20 layer supports Zn²⁺ ions with abundant transmission paths and a low Zn²⁺ migration energy barrier, which doubly accelerates ion migration at the interface. This internal/surface dual acceleration strategy allows the BSSE to deliver high ionic conductivity and Zn²⁺ transference number. Both the Zn∥Zn symmetric and Zn∥MnO₂ full cells exhibit an obvious prolonged cycle life. This dual acceleration strategy sheds light on the design of high-ionic-conductivity, steady, and practical ZIBs.