Segmental molecular dynamics boosts Li-ion conduction in metal-organic solid electrolytes for Li-metal batteries

Metal-organic frameworks have emerged as a promising class of solid electrolytes for Li batteries. However, previous efforts to enhance Li-ion conductivity exclusively rely on the incorporation of solvents/salts and modifications of the rigid frameworks. In this study, we demonstrate metal-organic solid electrolytes with superionic conductivity by grafting hemilabile anionic chains with segmental motions in the pore channels of an Al-based metal-organic framework. High room-temperature ionic conductivity of 1.4×10–5 and 1.1×10−3 S cm–1 have been achieved under solvent-free and lean-solvent conditions, respectively. Solid-state nuclear magnetic resonance analysis reveals the localized molecular rotation and vibration of the anionic chains within in the rigid framework. Such segmental molecular dynamics would build Li transport highways and facilitate the Li-ion transport even without solvent. The metal-organic solid electrolyte shows excellent stability against Li metal anode, and the as-developed Li-metal batteries exhibit remarkable rate performance up to 4 C and long lifespan over 300 cycles. This work sheds light on the design principles of advanced metal-organic solid electrolytes for solid-state Li batteries.