All-solid-state batteries with solid electrolytes having ionic conductivities in the range of those of liquid electrolytes have gained much interest as safety is still a major issue for applications. Meanwhile, lithium metal seems to be the anode material of choice to face the demand for higher capacities. Still, the main challenges that come with the use of a lithium metal anode, i.e., formation and growth of lithium dendrites, are still not understood very well. This work focuses on the reasons of the lifetime behavior of lithium symmetric cells with the solid electrolyte Li 6 PS 5 Cl and lithium electrode. In particular, the voltage increases during the application of a constant current density are investigated. The interface between the lithium metal electrode and the solid electrolyte is analyzed by X-ray photoelectron spectroscopy, and the resistance changes of each electrode during stripping and plating are investigated by impedance spectroscopy on a three-electrode cell. A main factor for the lifetime influenced by lithium dendrite formation and growth is the buildup of a lithium vacancy gradient, leading to voids which decrease the interface area and therefore increase the local current density. Additionally, those lithium vacancies in lithium metal represent a limitation for conductivity rather than migration in solid electrolyte. Further experiments indicate that the seedlike plating behavior of lithium also plays a key role in increased local current density and therefore decreased lifetime. Plating of only a small amount of lithium leads to small areas of well-connected interfaces, resulting in high local current density. A medium amount of plated lithium leads to larger areas of interface between lithium and electrolyte, balancing the current density distribution. In contrast, a high amount of repeatedly deposited lithium leads to lithium seed plating on top of already plated lithium. Those seed spots grown on top represent a better interface connection, which again leads to higher local current densities at those spots and therefore results in shorter lifetimes due to short circuits caused by lithium dendrites.

Compounds of stoichiometry (pe),(PF,) " , x 0.8CH 2 CI 2 (I)(pe = perylene),(peh(AsF 6 )" x 0.7 CH 2 CI 2 (2), (peh(PF 6 )1.4 x 0:6 THF (3), (peh(AsF6)1.5 x 0.5 THF (4) and (peh(SbF6h x 0.75 CH 2 C1 2 (5) have been obtained as crystalline samples by electrochemical deposition from CH 2 Cl 2 [(I), (2) and (5)J or from THF [(3) and (

Temperature dependent dc and microwave conjuctivity data together with EPR and optical reflectance measurements on the~mixedHsystem (pe)2(AsF 6)0,75(PF 6)0,35 x 0,85 CH 2 C1 2 are described. The data prove metallic behaviour of this organic solid down to 200 K.

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In the recent years, all-solid-state batteries have attracted much attention as they are safer in terms of flammability compared to liquid electrolyte systems. There are polymer, oxidic, and sulfidic solid electrolytes with advantages and disadvantages. One major advantage of sulfidic electrolytes is their high ionic conductivity at room temperature which is even comparable with that of liquid electrolytes. Another feature is the possible usability of lithium anodes in this system which leads to very high energy density. One major challenge of the lithium metal anode is the formation and growth of lithium dendrites which results in short circuits. A lot of research is done to prevent dendrite growth but more research is needed to understand the actual dendrite growth mechanism [1]. In our work we analyzed the reasons for increase of overpotentials that is very likely related to lithium dendrite growth in symmetric lithium metal cells with solid electrolyte Li6PS5Cl. In a three-electrode set up, the interface of a lithium symmetric cell is analyzed during stripping and plating with electrochemical impedance spectroscopy. The changes of the resistance contributions are discussed in terms of possible major mechanisms that are involved in lithium dendrite growth. Furthermore, the plating behavior of lithium is investigated which gives insight into possible onset for lithium dendrite growth. Reference s : [1] Xin-Bing Cheng, Rui Zhang, Chen-Zi Zhao, and Qiang Zhang, Toward Safe Lithium Metal Anode in Rechargeable Batteries: A Review, Chem. Rev. 2017, 117, 10403−10473.