Towards High-Performance Metal-Organic-Framework-Based Solid-State Electrolytes: Tunable Structures and Electrochemical Properties

Metal–organic frameworks (MOFs) have been reported as promising solid-state electrolytes owing to their tunable porous structures and ion-sieving capability. However, it remains challenging to rationally design high-performance MOF electrolytes. Herein, we controllably synthesized a series of MOFs to study the effects of pore apertures and open metal sites on ion-transport properties and electrochemical stability of MOF electrolytes. We demonstrate that MOFs with non-redox-active metal centers can lead to a wider electrochemical stability window than those with redox-active centers. Pore aperture of MOFs dominates the uptake of lithium salt and thus ionic conductivity. Ab initio molecular dynamics simulations further demonstrate that open metal sites of MOFs can immobilize anions of lithium salt via Lewis acid–base interaction, leading to a high lithium-ion transference number. This work provides not only a platform for studying ion-transport properties in tunable MOF electrolytes, but also a design strategy for MOF electrolytes with the guide of structure–property relationships.