Three-Dimensional Garnet Framework-Reinforced Solid Composite Electrolytes with High Lithium-Ion Conductivity and Excellent Stability.

We report a three-dimensional (3D) garnet framework-reinforced solid composite electrolyte with enhanced Li-ion conductivity and excellent thermal, mechanical, and electrochemical stabilities. The 3D garnet framework is fabricated via the polymeric sponge method, using low-cost polyurethane foam as the template. The interconnected 3D garnet framework not only reinforces the composite electrolyte but also forms continuous Li-ion transport pathways, thereby increasing the ionic conductivity. The 3D garnet composite electrolyte shows an ionic conductivity of 1.2 × 10-4 S cm-1 at 30 °C, about two times as high as that of the garnet particle-reinforced composite electrolyte. The Li-Li symmetric cell based on the 3D garnet composite electrolyte can be cycled more than 360 h without short circuit, suggesting an improved ability to suppress Li-dendrites. The Li/3D garnet composite electrolyte/LiFePO4 battery demonstrates stable cycling performance at 0.5 C. Owing to the cost-saving characteristics, the 3D garnet-reinforced solid composite electrolyte is promising for mass production.