Inhaltspezifische Aktionen

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 C2- as well as F- mass fragments. The C2-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 C2- as well as F- distribution at the SEI surface. The C2- image reveals the struture of the hard carbon electrode.