Ionic liquid confined in MOF/polymerized ionic network core-shell host as a solid electrolyte for lithium batteries

• MOF-based core-shell host loading ionic liquids (ILs) as lithium-ion battery composite electrolytes with high ionic conductivity over 4×10 -4 S cm -1 at 25 o C. • Increased lithium-ions transference number of the MOF@PIN-IL electrolyte that liberates Li ions and facilitate their transportation owing to the strong interactions between MOF@PIN and the mobile anions in IL. • Improved rate capability of MOF@PIN -IL based batteries after long cycling-lifetime compared with bare IL electrolytes. Although the low t Li + and fluid nature of ionic liquid electrolytes can lead to weakened rate capability and higher leakage risks, these challenges can be tackled by incorporating ILs into solid hosts with controlled properties. Herein, we designed a heterogeneous metal organic framework (MOF)/polymerized ionic network (PIN) core-shell composite as a porous host for IL N,N-diethyl-N-(2-methoxyethyl)-N-methylammonium bis(trifluoromethylsulphonyl)imide (DEME-TFSI). The PIN shell with abundant ionic structures exhibit nice compatibility with ILs to achieve high loading, while the MOF core has narrow nanopores to confine large anions in ILs and enhance Li + selectivity. The as-synthesized conductive solid electrolyte (HKUST@PIN-IL-Li) showed high IL loading, high ionic conductivity over 4×10 -4 S cm -1 at 25 o C and increased Li + transfer number (0.367) in comparison to hollow H-PIN-IL-Li and bare IL-Li electrolyte. Overall, our research demonstrates for the first time a novel MOF@PIN core-shell structure as a solid framework for IL with high battery performance.