Solvent-Free Synthesis of Thin, Flexible, Nonflammable Garnet-Based Composite Solid Electrolyte for All-Solid-State Lithium Batteries

Thin solid-state electrolytes with nonflammability, high ionic conductivity, low interfacial resistance, and good processability are urgently required for next-generation safe, high energy density lithium metal batteries. Here, a 3D Li6.75La3Zr1.75Ta0.25O12 (LLZTO) self-supporting framework interconnected by polytetrafluoroethylene (PTFE) binder is prepared through a simple grinding method without any solvent. Subsequently, a garnet-based composite electrolyte is achieved through filling the flexible 3D LLZTO framework with a succinonitrile solid electrolyte. Due to the high content of garnet ceramic (80.4 wt%) and high heat-resistance of the PTFE binder, such a composite electrolyte film with nonflammability and high processability exhibits a wide electrochemical window of 4.8 V versus Li/Li+ and high ionic transference number of 0.53. The continuous Li+ transfer channels between interconnected LLZTO particles and succinonitrile, and the soft electrolyte/electrode interface jointly contribute to a high ambient-temperature ionic conductivity of 1.2 x 10(-4) S cm(-1) and excellent long-term stability of the Li symmetric battery (stable at a current density of 0.1 mA cm(-2) for over 500 h). Furthermore, as-prepared LiFePO4|Li and LiNi0.5Mn0.3Co0.2O2|Li batteries based on the thin composite electrolyte exhibit high discharge specific capacities of 153 and 158 mAh g(-1) respectively, and desirable cyclic stabilities at room temperature.