In the pursuit of urgently needed, energy dense solid-state batteries for electric vehicle and portable electronics applications, halide solid electrolytes offer a promising path forward with exceptional compatibility against high-voltage oxide electrodes, tunable ionic conductivities, and facile processing. For this family of compounds, synthesis protocols strongly affect cation site disorder and modulate Li + mobility. In this work, we reveal the presence of a high concentration of stacking faults in the superionic conductor Li 3 YCl 6 and demonstrate a method of controlling its Li + conductivity by tuning the defect concentration with synthesis and heat treatments at select temperatures. Leveraging complementary insights from variable temperature synchrotron X-ray diffraction, neutron diffraction, cryogenic transmission electron microscopy, solid-state nuclear magnetic resonance, density functional theory, and electrochemical impedance spectroscopy, we identify the nature of planar defects and the role of nonstoichiometry in lowering Li + migration barriers and increasing Li site connectivity in mechanochemically synthesized Li 3 YCl 6 . We harness paramagnetic relaxation enhancement to enable 89 Y solid-state NMR and directly contrast the Y cation site disorder resulting from different preparation methods, demonstrating a potent tool for other researchers studying Y-containing compositions. With heat treatments at temperatures as low as 333 K (60 °C), we decrease the concentration of planar defects, demonstrating a simple method for tuning the Li + conductivity. Findings from this work are expected to be generalizable to other halide solid electrolyte candidates and provide an improved understanding of defect-enabled Li + conduction in this class of Li-ion conductors.

A series of Zr-based UiO-n MOF materials (n = 66, 67, 68) have been studied for iodine capture. Gaseous iodine adsorption was collected kinetically from a home-made setup allowing the continuous measurement of iodine content trapped within UiO-n compounds, with organic functionalities (À H, À CH 3 , À Cl, À Br, À (OH) 2 , À NO 2 , À NH 2 , (À NH 2 ) 2 , À CH 2 NH 2 ) by in-situ UV-Vis spectroscopy. This study emphasizes the role of the amino groups attached to the aromatic rings of the ligands connecting the {Zr 6 O 4 (OH) 4 } brick. In particular, the preferential interaction of iodine with lone-pair groups, such as amino functions, has been experimentally observed and is also based on DFT calculations. Indeed, higher iodine contents were systematically measured for amino-functional-ized UiO-66 or UiO-67, compared to the pristine material (up to 1211 mg/g for UiO-67-(NH 2 ) 2 ). However, DFT calculations revealed the highest computed interaction energies for alkylamine groups (À CH 2 NH 2 ) in UiO-67 (À 128.5 kJ/mol for the octahedral cavity), and pointed out the influence of this specific functionality compared with that of an aromatic amine. The encapsulation of iodine within the pore system of UiO-n materials and their amino-derivatives has been analyzed by UV-Vis and Raman spectroscopy. We showed that a systematic conversion of molecular iodine (I 2 ) species into anionic I À ones, stabilized as I À •••I 2 or I 3 À complexes within the MOF cavities, occurs when I 2 @UiO-n samples are left in ambient light.

We report the study of the resistance of archetypal MOFs (MILs, HKUST-1, UiO-66, and ZIF-8) under gamma irradiation. The different porous solids were irradiated with doses up to 1.75 MGy. All the MOFs constructed with transition metals (Cu, Zn, Zr) exhibit an evident destruction of the framework, whereas the compounds constructed with aluminium remain intact.