High Li ⁺ and Na ⁺ Conductivity in New Hybrid Solid Electrolytes based on the Porous MIL‐121 Metal Organic Framework

Solid-state electrolytes (SSEs) can leapfrog the development of all-solid-state batteries (ASSBs), enabling them to power electric vehicles and store renewable energy from intermittent sources. Here, a new hybrid Li+ Na+ conducting SSE based on MIL-121 metal-organic framework (MOF) structure is reported. Following synthesis activation MOF, free carboxylic units along 1D pores are functionalized with or ions by ion exchange. Ion dynamics investigated broadband impedance spectroscopy 7Li 23Na NMR spin-lattice relaxation. A crossover at 50 °C (Li+) 10 (Na+) correlated almost uncorrelated motion higher temperature observed, which in line Ngai's coupling model. Alternatively, accordance jump relaxation model Funke, low only fraction processes successful as lattice rearrangement direct vicinity slow. 1H unambiguously shows that main charge carrier. Conductivities reach 0.1 mS cm−1 (298 K, Na+) while energies 0.28 eV 0.36 (Na+). The findings pave way towards easily tunable rationally adjustable high-performance MOF-based SSEs for ASSBs.