3D Coral-like LLZO/PVDF Composite Electrolytes with Enhanced Ionic Conductivity and Mechanical Flexibility for Solid-State Lithium Batteries

Composite polymer electrolytes (CPEs) are very promising for high-energy lithium-metal batteries as they combine the advantages of polymeric and ceramic electrolytes. The dimensions and morphologies of active ceramic fillers play critical roles in determining the electrochemical and mechanical performances of CPEs. Herein, a coral-like LLZO (Li_6.4La₃Zr₂Al_0.2O₁₂) is designed and used as a 3D active nanofiller in a poly(vinylidene difluoride) polymer matrix. Building 3D interconnected frameworks endows the as-made CPE membranes with an enhanced ionic conductivity (1.51 × 10^-4 S cm^-1) at room temperature and an enlarged tensile strength up to 5.9 MPa. As a consequence, the flexible 3D-architectured CPE enables a steady lithium plating/stripping cycling over 200 h without a short circuit. Moreover, the assembled solid-state Li|LiFePO₄ cells using the electrolyte exhibit decent cycling performance (95.2% capacity retention after 200 cycles at 1 C) and excellent rate capability (120 mA h g^-1 at 3 C). These results demonstrate the superiority of 3D interconnected garnet frameworks in developing CPEs with excellent electrochemical and mechanical properties.