Li+- and Na+-conducting thiophosphates have attracted much interest because of their intrinsically high ionic conductivities and the possibility to be employed in solid-state batteries. Inspired by the recent finding of the influence of changing lattice vibrations and induced lattice softening on the ionic transport of Li+-conducting electrolytes, here we explore this effect in the Na+ conductor Na3PS4–x Se x . Ultrasonic speed of sound measurements are used to monitor a changing lattice stiffness and Debye frequencies. The changes in the lattice dynamics are complemented by X-ray diffraction and electrochemical impedance spectroscopy. With systematic alteration of the polarizability of the anion framework, a softening of the lattice can be observed that leads to a reduction of the activation barrier for migration as well as a decreased Arrhenius prefactor. This work shows that, similar to Li+ transport, the softening of the average vibrational frequencies of the lattice has a tremendous effect on Na+-ionic transport and that ion–phonon interactions need to be considered in solid electrolytes.

One limiting phenomenon for the cycle life of metal–oxygen batteries is the growth of dendrites during metal plating (cell charging). For the relatively new sodium–oxygen cell, this subject has been scarcely investigated, until now. Therefore, dendrite formation is systematically investigated herein, with the aim of gaining a more detailed understanding of the underlying mechanisms and relevant control parameters. Electrochemical impedance spectroscopy, cycling experiments, and optical characterization techniques are applied in situ and ex situ; sodium dendrite growth is directly visualized, for the first time, by means of a tubular glass cell. The growth of instable surface morphologies is discussed from a theoretical perspective to comprehend the experimentally observed dendrite growth. Furthermore, countermeasures against issues with dendrites are discussed, with the aim of increasing the cycle life of sodium–oxygen batteries.

The development of high energy‐density and low‐cost energy storage devices requires new chemistry beyond the horizon of current state‐of‐the‐art lithium‐ion batteries. Recently, sodium/oxygen (Na/O2) batteries have attracted great attention as one possible battery type among the new generation of rechargeable batteries. They convince with superior energy density, a relatively simple cell reaction, and abundance of sodium. Research on Na/O2 batteries has progressed quickly in recent years. However, a fundamental understanding underpinning the complex chemical/electrochemical side reactions is still insufficient, and many challenges remain unsolved for real practical applications. Herein, recent achievements and remaining issues for the development of rechargeable Na/O2 batteries are summarized. The discussion focuses on cell reaction mechanisms as well as cathode materials, sodium anodes, and electrolytes as key components of this type of battery. Furthermore, perspectives for future research and technological advances of Na/O2 batteries are outlined.

Abstract. Na 3 SbSe 3 was obtained by solid state reaction of anhydrous Na 2 Se, antimony, and selenium in a ratio of 3:2:3. It is air and moisture sensitive and melts at 870 K. Yellow single crystals of Na 3 SbSe 3 were used for single-crystal X-ray diffraction. It crystallizes in the cubic space group P2 1 3 (No. 198) with a = 9.0227(2) Å, V = 734.53(3) Å 3 , and Z = 4. Na 3 SbS 3 is isotypic with Na 3 AsS 3 . Trigonal SbSe 3 pyramids therein act as mono-, bi-, and tridentate ligands to sodium. Sodium is

Abstract. Na 3 SbS 3 was prepared by the reaction of anhydrous Na 2 S, antimony, and sulfur in a ratio of 3:2:3 at 870 K. The pale yellow compound is air and moisture sensitive. A microcrystalline sample was obtained after annealing Na 3 SbS 3 for two weeks at 720 K. The crystal structure of Na 3 SbS 3 was determined by single-crystal X-ray diffraction at 123 K. Na 3 SbS 3 crystallizes in the cubic space group P2 1 3 (No. 198) with a = 8.6420(1) Å, V = 645.42(1) Å 3 and Z = 4. The structure refinement converged to R = 0.0099 (wR = 0.0181) for 592 independent reflections and 23 parameters. Na 3 SbS 3 is isotypic with Na 3 AsS 3 . Sodium atoms are located on three different sites, which show a