LAUSR

Metal-organic frameworks (MOFs) have been reported as promising materials for various electrochemical applications owing to their tunable porous structures and ion-sieving capability. However, it remains challenging to rationally design high-performance MOF-based electrolytes for high-energy lithium batteries. Herein, by combining advanced characterization and modeling tools, we designed a series of nanocrystalline MOFs and systematically studied the effects of pore apertures and open metal sites on ion-transport properties and electrochemical stability of MOF quasi-solid-state electrolytes. We demonstrate that MOFs with non-redox-active metal centers can lead to much wider electrochemical stability window than those with redox-active centers. Furthermore, our results suggest that pore aperture of MOFs is a dominating factor that determines the uptake of lithium salt and thus ionic conductivity. The ab initio molecular dynamics (AIMD) simulations further demonstrate that open metal sites of MOFs can facilitate the dissociation of lithium salt and immobilize anions via Lewis acid-base interaction, leading to good lithium-ion mobility and high transference number. Such host-guest interaction was further quantitatively studied by cluster-model DFT calculations at the atomic level, which was confirmed by X-ray absorption near edge structure analysis. Besides, the vehicle-type ion conduction mechanism in MOFs were revealed by AIMD simulations and solid-state NMR results. Benefiting from good electrochemical stability and thin/dense structure, the MOF quasi-solid-state electrolyte demonstrates excellent battery performance with commercial LiFePO4 cathodes (>500 cycles at 0.5 C) and LiCoO2 cathodes (up to 4.6 V) at 30°C. This work provides new insights into structure-property relationships between tunable structure and electrochemical properties of MOFs that can lead to the development of advanced quasi-solid-state electrolytes for high-energy lithium batteries. This article is protected by copyright. All rights reserved.