20 μm-Thick Li6.4La3Zr1.4Ta0.6O12-Based Flexible Solid Electrolytes for All-Solid-State Lithium Batteries

The doped garnet-type solid electrolytes are attracting great interest due to high ionic conductivity and excellent electrochemical stability against Li metal. However, the thick electrolyte layer and rigid nature as well as poor interfacial contact are huge obstacles for its application in all-solid-state lithium batteries. Herein, an ultrathin flexible Li6.4La3Zr1.4Ta0.6O12- (LLZTO-) based solid electrolyte with 90 wt% LLZTO content is realized through solvent-free procedure. The resultant 20 μm-thick LLZTO-based film exhibits ultrahigh ionic conductance of 41.21 mS at 30°C, excellent oxidation stability of 4.6 V, superior thermal stability and nonflammability. Moreover, the corresponding Li||Li symmetric cell can stable cycle for more than 2000 h with low overpotential at 0.1 mA cm-2 under 60°C. The assembled Li||LiFePO4 pouch cell with integrated electrolyte/cathode interface exhibits excellent rate performances and cycle performances with a capacity retention of 71.4% from 153 mAh g-1 to 109.2 mAh g-1 at 0.1 C over 500 cycles under 60°C. This work provides a promising strategy towards realizing ultrathin flexible solid electrolyte for high-performance all-solid-state lithium batteries.