Molecular coordination-doping engineering enables adjustable ion transport channel based on MOFs-derived UIOLiTF-LLZTO ionic conductor

Abstract

The inferior ionic conductivity of composite polymer electrolytes (CPEs) caused by grain boundary impedance is one of the critical issues. Adjustable ion transport channels at the molecular level can improve ionic conductivity and lithium-ion transference number. Herein, UIO-66-NSO2CF3Li-Li6.4La3Zr1.4Ta0.6O12 (UIOLiTF-LLZTO) ionic conductor derived from metal-organic frameworks (MOFs) was designed by a covalent grafted strategy of trifluoromethylsulfonyl (TF) group on UIOLiTF and a doping process of LLZTO, showing two new lithium-ion transfer channels driven by molecular coordination-doping engineering. The first channel along UIOLiTF-UIOLiTF was constructed due to the existence of the TF group on UIOLiTF. The second channel along UIOLiTF-LLZTO was constructed due to the direct nanometer contact interface between the opened channel of UIOLiTF and LLZTO. Then TF group acts as “claws” to capture and transfer lithium-ion along the different channels, facilitating improving ionic conductivity and reducing grain boundary impedance. Benefiting from the molecular coordination-doping engineering, UIOLiTF-LLZTO exhibits high ionic conductivity of 9.86 × 10–4 S cm–1, a large lithium-ion transference number of 0.79, and a wide electrochemical window of 5.35 V. Meanwhile, all-solid-state Li|UIOLiTF-LLZTO|LiFePO4 batteries show a high specific capacity of 164.5 mAh g–1 and 155.6 mAh g–1 at 0.2 C and 0.5 C, respectively. Therefore, UIOLiTF-LLZTO demonstrates the way towards the development of MOFs-based CPEs for all-solid-state lithium batteries with high performance.