A highly ion-conductive three-dimensional LLZAO-PEO/LiTFSI solid electrolyte for high-performance solid-state batteries

Composite solid electrolytes have recently attracted widespread attention due to their acceptable lithium-ion (Li-ion) conductivity and suitable flexibility. However, isolated ceramic particles in composite electrolyte cannot provide continuous fast Li-ion transport channels. And the non-uniformity caused by particle agglomeration usually leads to a decrease in the performance of the composite electrolyte. Here, we design a “polymer in ceramic” composite electrolyte that combines three-dimensional Li 6.4 La 3 Zr 2 Al 0.2 O 12 (3D LLZAO) framework with polyethylene oxide (PEO)/LiTFSI (T-LAPL) via a template and solution method. In addition to the significantly enhanced Li-ion conductivity (2.51 × 10 −4 S cm −1 at room temperature) and the high Li-ion transference number (t Li+  = 0.53), the T-LAPL composite electrolyte also exhibits improved thermal and electrochemical stability. Both symmetrical Li/T-LAPL/Li cells and LiFePO 4 /T-LAPL/Li cells display excellent electrochemical performance. The repeated lithium stripping/plating process at 0.1 mA cm −2 can keep stable for 400 h without short circuit at room temperature. The assembled LiFePO 4 cell shows an initial discharge capacity of 165.9 mAh g −1 at 0.2C and the capacity can remain 80% after 100 cycles. This high-performance composite electrolyte reveals a promising opportunity for the next-generation lithium batteries with high energy density and high safety.