Thermal initiation/ultraviolet cross-linking process in polyethylene oxide@Li_6?75La₃Zr_1?75Ta_0?25O ₁₂-based composite electrolyte with high room-temperature ionic conductivity and long life cycle

Organic-inorganic composite electrolytes (PL-SCEs) based on polyethylene oxide (PEO) and Li6 center dot 75La3Zr1 center dot 75Ta0 center dot 25O12 (LLZTO) are considered to be one of the most promising solid electrolytes. However, the low room-temperature ionic conductivity caused by the inherent high crystallinity of PEO severely hinders its practical application. Herein, a novel PL-SCE is synthesized through a facile thermal induction and ultraviolet crosslinking process, using fluoroethylene carbonate (FEC) and 4-methylbenzophenone as thermal/ultraviolet triggers, and tetraethylene glycol dimethyl ether (TEGDME) as an ion conductive plasticizer. The F atom in the FEC can attack the C-O bond in the PEO chain and abstract the hydrogen attached to the C atom to form an active site, prompt TEGDME and PEO to achieve a higher degree of cross-linking, thus endowing PL-SCE with high Li-ion conductivity of 5.35 x 10(-4) S cm(-1) at 25 degrees C. Besides, the obtained PL-SCE exhibits excellent wettability and compatibility with Li metal anodes, the interfacial impedance is only 44 Omega cm(2). The LiFePO4 parallel to Li full cell based on the proposed PL-SCE exhibits an excellent room-temperature cycling performance with a capacity retention rate up to 88% and the average Coulombic efficiency above 98% upon 450 cycles at 1 C. Prospectively, this work provides a promising alternative method for the practical application of PL-SCEs.