Elucidation of the structure of a new sodium superionic conductor, Na11Sn2PS12via single crystal XRD and AIMD simulations reveal isotropic 3D Na+-ion conduction pathways.

Argyrodites, Li6PS5X (X = Cl, Br), are considered to be one of the most promising solid-state electrolytes for solid-state batteries. However, while traditional ball-mill approaches to prepare these materials do not promote scale-up, solution-based preparative methods have resulted in poor ionic conductivity. Herein, we report a solution-engineered, scalable approach to these materials, including the new argyrodite solid solution phase Li6–y PS5–y Cl1+y (y = 0–0.5), that shows very high ionic conductivities (up to 3.9 mS·cm–1) and negligible electronic conductivities. These properties are almost the same as their analogues prepared by solid-state methods, owing to a lack of amorphous contributions and low impurity contents ranging from 3 to 10%. Electrochemical performance is demonstrated for Li6PS5Cl in a prototype solid-state battery and compared to that of the same solid electrolyte derived from classic ball-milling processing.

Solid electrolytes that are chemically stable and have a high ionic conductivity would dramatically enhance the safety and operating lifespan of rechargeable lithium batteries. Here, we apply a multi-technique approach to the Li-ion conducting system (1-z)Li4SiO4-(z)Li3PO4 with the aim of developing a solid electrolyte with enhanced ionic conductivity. Previously unidentified superstructure and immiscibility features in high-purity samples are characterized by X-ray and neutron diffraction across a range of compositions (z = 0.0-1.0). Ionic conductivities from AC impedance measurements and large-scale molecular dynamics (MD) simulations are in good agreement, showing very low values in the parent phases (Li4SiO4 and Li3PO4) but orders of magnitude higher conductivities (10(-3) S/cm at 573 K) in the mixed compositions. The MD simulations reveal new mechanistic insights into the mixed Si/P compositions in which Li-ion conduction occurs through 3D pathways and a cooperative interstitial mechanism; such correlated motion is a key factor in promoting high ionic conductivity. Solid-state (6)Li, (7)Li, and (31)P NMR experiments reveal enhanced local Li-ion dynamics and atomic disorder in the solid solutions, which are correlated to the ionic diffusivity. These unique insights will be valuable in developing strategies to optimize the ionic conductivity in this system and to identify next-generation solid electrolytes.

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The crystal chemistry and the electrochemical properties upon Na + extraction/insertion of NASICON-type Na 3 Al y V 2Ày (PO 4 ) 3 compositions (y ¼ 0.1, 0.25 and 0.5) were investigated. It was found that this family of V/Al substituted NASICON materials undergoes multiple reversible phase transitions between À50 C and 250 C upon heating, from monoclinic to rhombohedral symmetry, related to progressive disordering of Na + ions within the framework. Na + insertion/extraction mechanisms were monitored by operando X-ray diffraction. It is shown for the first time that substitution of aluminum for vanadium in Na 3 Al 0.5 V 1.5 (PO 4 ) 3 increases significantly the theoretical energy density of these promising positive electrodes (425 W h kg À1 ) due to its lighter molecular weight and the possibility of reversible operation on the V 4+ /V 5+ redox couple at 3.95 V vs. Na + /Na.

Experimental details, refinement data, Arrhenius plot, the Nyquist impedance plot and bond lengths (PDF) Data for Na 11.08 S 12 SbSn 2 (CIF) Data for Na 11.10 PS 12 Sn 2 (CIF)

Na2TiV(PO4)3 was synthesized by soft chemical oxidation. The system shows three electron exchange for 2 transition metals. Coupled X-ray diffraction/electrochemical studies were performed, operando.

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