Sandwich Structured Metal oxide/Reduced Graphene Oxide/Metal Oxide‐Based Polymer Electrolyte Enables Continuous Inorganic–Organic Interphase for Fast Lithium‐Ion Transportation

Abstract Introducing inorganic fillers into organic poly(ethylene oxide)(PEO)‐based electrolyte has attracted substantial attention to enhance its ionic conductivity and mechanical strength, but limited inorganic–organic interphases are always caused by isolated particles agglomeration. Herein, a variety of sandwich structured metal oxide/reduced graphene oxide(rGO)/metal oxide nanocomposites to optimize lithium‐ion conduction by interconnected amorphous organic–inorganic interphases in lithium metal batteries, are proposed. With the support of high surface area rGO, the agglomeration of metal oxide particles is precluded, forming continuous amorphous organic–inorganic interphases with stacked layer‐by‐layer structure, thus creating 3D interconnected lithium‐ion transportation channels vertically and laterally. Besides, metal oxide nanoparticles with hydroxyls possess high affinity toward bis(tri‐fluoromethanesulfonyl)imide anions by hydrogen bindings between hydroxyls and fluorine and metal‐oxygen bonds, releasing more free lithium ions. Consequently, PEO‐ZnO/rGO/ZnO electrolyte delivers superior ionic conductivity of 1.02 × 10 −4 S cm −1 at 25 °C and lithium‐ion transference number of 0.38 at 60 °C. Furthermore, ZnO/rGO/ZnO insertion promotes the formation of LiF‐rich stable solid electrolyte interface, endowing Li symmetric cells with long‐term cycling stability over 900 hours. The corresponding LiFePO 4 cathode possesses a high reversible specific capacity of 130 mAh g −1 at 0.5C after cycling 300 cycles with a poor capacity fading of 0.05% per cycle.