SIMS, Plasmas & Materials
Welcome on the webpage of the SIMS, Plasmas and Materials group. On these webpages, you can find information about the direction, the area of research, the publications and the teaching. As a subgroup, we are part of the WG Janek. At first glance, “SIMS, Plasmas and Materials” appears to be a very diverse combination of topics. At second glance, an analytical technique like secondary ion mass spectrometry (SIMS) requires materials for analysis. Only specialist knowledge in the field of analytics and materials science enables maximum outcomes. The main interest lies in the investigation of diffusion processes in applied materials systems. This ranges from drug release from biomaterials and transport into bone, via diffusion in environmental polymers through materials degradation in low-temperature plasmas. A particular challenge lies in SIMS in-situ investigations of electrochemical systems, like solid oxide fuel cell electrodes and batteries.
Within the POLIS Cluster of Excellence we are investigating the formation, stability and interfacial kinetics of the SEI (Solid Electrolyte Interface) layer on hard carbon anodes in Na batteries. The investigations are carried out in an electrochemical cell with a Na cathode and most commonly used organic electrolytes, such as cyclic propylene carbonate (PC) and ethylene carbonate (EC). The SEI characterisation is carried out by XPS and ToF-SIMS in combination with statistical data analysis methodes like Multiple Curve Resolution (MCR). A stable SEI is a prerequisite for a long term cycle stability of the battery and its transport properties can determine the cellular kinetics. In the Figure 1 an exemplary SIMS depth profile MCR analysis of the SEI layer on an hard carbon electrode is shown. It shows a layered structure with different organic and inorganic layers. Figure 2 shows mass images of the lateral distribution of the C
2
-
as well as F
-
mass fragments. The C
2
-
image visualizes the hard carbon structure. The F- is an SEI component, which is inhomogeneously distributed at the SEI surface.
Figure 1: 5 factor MCR-Analysis of a ToF-SIMS depth profile of the SEI on a Hard Carbon electrode from a sodium-ion battery. bottom: graphical depiction of the results above.
Figure 2: Mass images that show C 2 - as well as F - distribution at the SEI surface. The C 2 - image reveals the struture of the hard carbon electrode.