Rational design of fireproof fiber-network reinforced 3D composite solid electrolyte for dendrite-free solid-state batteries

• 3D XRM is employed to visualize the internal composition, structure and morphology of solid-electrolyte. • The solid electrolyte exhibits stable Li plating/stripping cycle over 1000 h. • The NCM622/Li, NCM622/Graphite and NCM622/Si-Graphite batteries show good cycle stability at room temperature. Rationally constructing composite solid electrolyte (CSE) with high ionic conductivity, mechanically strong, and nonflammability is considered as an effective strategy to meet the urgent needs for high-safety and high-energy density batteries. Herein, we report the design of a fiber-network reinforced 3D CSE with a flexible, mechanically strong, nonflammable and porous PI film as the host, and Li 6.75 La 3 Zr 1.75 Ta 0.25 O 12 (LLZTO) and poly (propylene carbonate) (PPC) polymer matrix as the ionically conducting filler. The homogeneously and continuously distribution of LLZTO fillers in CSE is conductive to the rapid Li + transmission and uniform Li + deposition. Meanwhile, the mechanically robust PI host can effectively suppress Li dendrite growth by constructing physical obstacles in inner structure of CSE. Benefiting from these merits, the as-prepared PI-PPC/LLZTO CSE exhibits high ionic conductivity of 2.7 × 10 -4 S cm −1 at 30 °C and excellent tensile strength of 11.78 MPa. The 3D CSE enables highly stable Li plating/stripping cycle for over 1000 h at 0.1 mA cm −2 at 25 °C. The LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622)/PI-PPC/LLZTO CSE/Li cells demonstrate good cycling stability (0.2 C) and rate performances at room temperature. Furthermore, the NCM622/Graphite (Gr) and NCM622/Si-Gr full solid batteries based on PI-PPC/LLZTO CSE also deliver good cycle stability, which further broadens the application fields of this fiber-network reinforced 3D CSE in different battery systems.