Li(+) Dynamics of Liquid Electrolytes Nanoconfined in Metal-Organic Frameworks.

Metal-organic frameworks (MOFs) are excellent platforms to design hybrid electrolytes for Li batteries with liquid-like transport and stability against lithium dendrites. We report on Li(+) dynamics in quasi-solid electrolytes consisting in Mg-MOF-74 soaked with LiClO(4)-propylene carbonate (PC) and LiClO(4)-ethylene carbonate (EC)/dimethyl carbonate (DMC) solutions by combining studies of ion conductivity, nuclear magnetic resonance (NMR) characterization, and spin relaxometry. We investigate nanoconfinement of liquid inside MOFs to characterize the adsorption/solvation mechanism at the basis of Li(+) migration in these materials. NMR supports that the liquid is nanoconfined in framework micropores, strongly interacting with their walls and that the nature of the solvent affects Li(+) migration in MOFs. Contrary to the "free'' liquid electrolytes, faster ion dynamics and higher Li(+) mobility take place in LiClO(4)-PC electrolytes when nanoconfined in MOFs demonstrating superionic conductor behavior (conductivity σ(rt) > 0.1 mS cm(-1), transport number t(Li(+)) > 0.7). Such properties, including a more stable Li electrodeposition, make MOF-hybrid electrolytes promising for high-power and safer lithium-ion batteries.