“Polymer in ceramic” type LLZTO/PEO/PVDF composite electrolyte with high lithium migration number for solid-state lithium batteries

One of the effective methods to improve the energy density and safety of lithium metal batteries is to use composite solid electrolytes with high voltage and good performance. However, the low ionic conductivity at room temperature and the unsatisfactory Li+ migration number of composite solid electrolytes lead to the growth of lithium dendrites and the increase of internal resistance, which restricts the industrialization of composite electrolytes for solid-state lithium batteries. This work prepares a Li6.4La3Zr1.4Ta0.6O12 (LLZTO)/polyethylene oxide (PEO)/polyvinylidene fluoride (PVDF) composite electrolyte. In this “polymer in ceramic” type electrolyte, the combination of PEO with PVDF and LLZTO reduces the crystallinity of PEO and promotes the rapid migration of Li+ along the PEO polymer molecular chain through complexation and decomplexation. At the same time, LLZTO, which has an excellent ion conduction function, introduces new ion conduction channels when combined with PEO and PVDF, thereby further improving ion conductivity. The LP82 composite electrolyte has a Li+ migration number of 0.78 and an electrochemical stability window of 5.5 V and exhibits excellent flexibility. The Li/LP82 electrolyte/Li battery has a relatively stable voltage of 0.04 V at 0.1 mA cm−2 and a stable cycling of 1000 h. The discharge specific capacity of the LiFePO4/LP82/Li battery is 144.4 mA h g−1 at 0.1 C after 180 cycles, and the capacity retention is 90.7%. This work provides a good reference for the preparation of composite electrolytes with simple processes, high voltage, and high performance.