Molecular Insights Shaping the Design of Metal–Organic Framework-Based Electrolytes

High Resolution Image Download MS PowerPoint Slide Understanding the molecular determinants of Li + transport in quasi-solid-state electrolytes (QSSEs) is critical for the design of next-generation energy storage materials. Here, we investigate Li + conduction in an isoreticular series of anionic metal–organic frameworks (MOFs), Li 3 [(Cu 4 Cl) 3 L 8 ] (L 3– = linker), to disentangle the effects of pore size and linker functionality on ion conductivity. Contrary to expectation based on previous studies, despite their structural differences, the MOFs show pore size-independent Li + conductivity, whereas the linker functional groups can impose an effect. Using 7 Li magic-angle-spinning solid-state nuclear magnetic resonance, we identify the major Li + conducting species residing in the open pore channels, which, upon the addition of propylene carbonate, display liquid-like transport with low activation energies. The similar local environments and liquid-like dynamics of these species give rise to conductivities on the order of 10 –5 S/cm across the isoreticular series, though the interactions between tetrazolate nitrogens in linkers and Li + restrict ion mobility, leading to a modest decrease in conductivity. This study provides molecular-level insights into Li + transport in anionic MOF-based electrolytes and thus establishes the design principles for developing efficient QSSEs.