A composite solid-state electrolyte of high ionic-conductivity garnet-type Li6.5La3Zr1.5Ta0.1Nb0.4O12 filler in PEO matrix

In this work, highly ionically conductive Li6.5La3Zr1.5Ta0.1Nb0.4O12 (LLZTNO) fillers were blended into a poly(ethylene oxide) matrix to construct a composite solid-state electrolyte (CSSE). The LLZTNO fillers decrease the crystallinity of the PEO and provide extra lithium-ion transport pathways. Additionally, TFSI− anions are immobilized by the LLZTNO ceramic powders, and more Li ions are mobilized, increasing the overall ionic conductivity in CSSE. The PEO-LiTFSI-10% LLZTNO (i.e., PL-LLZTNO10%) CSSE shows the highest conductivity of 0.36 × 10−4 S cm−1 with a broad voltage window of 4.7 V at room temperature. The Li/ PL-LLZTNO10% CSSE/Li symmetric cells could operate for approximately 1200 h at 63 mV polarization voltage. The assembled solid-state LFP/PL-LLZTNO10%/Li cells deliver a 158.3 mAh g−1 capacity at 0.2C and 60 °C. After 300 cycles, its specific discharge capacity remains at 143.5 mAh g−1 with a Coulombic efficiency of 99.54%.