In situ polymerization of 1,3‐dioxolane infiltrating 3D garnet framework with high ionic conductivity and excellent interfacial stability for integrated solid‐state Li metal battery

Abstract The polymer‐ceramic composite electrolyte is considered as one of promising electrolytes for solid‐state battery. However, in previous research, ceramic particles are usually dispersed in polymer matrix and could not form continuous Li + conductive channels. The agglomeration of ceramic particles could also lead to low ionic conductivity and poor interfacial electrode/electrolyte contact. In this paper, self‐supported porous Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZTO) electrolyte is synthesized by gelcasting process, which possesses three‐dimensional (3D) interconnected pore channels and relatively high strength. The 1,3‐dioxolane (DOL) could penetrate into the porous LLZTO framework for its excellent fluidity. The subsequent in situ polymerization process by thermal treatment could completely fill the internal pores and improve the interfacial contact with electrode. The resulting 3D composite electrolyte with dual continuous Li + transport channels in ceramic and polymer components exhibits high ionic conductivity of 2.8 × 10 –4 S·cm −1 at room temperature and low Li/electrolyte interfacial resistance of 94 Ω·cm 2 at 40 °C. The corresponding Li/Li symmetric cell delivers stable voltage profiles for over 600 h under 0.1 and 0.2 mA·cm −2 . The solid‐state Li/LiFePO 4 battery shows superior rate and cycling performance under 0.1C and 0.2C. This work guides the preparation of composite electrolyte with dual continuous Li + conductive paths as well as high ceramic ratio and interface modification strategy for solid‐state Li metal battery.