Bild des Monats Mai 2019
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Interfacial degradation in all solid-state batteries
All solid-state batteries (ASSBs) are expected to be a promising alternative to conventional lithium-ion batteries with liquid electrolytes (LIBs). In principle, high cell voltages and high specific capacities can be achieved with solid electrolytes (SE). In addition, safety aspects can be improved compared to conventional LIBs by avoiding flammable organic substances, which is particularly important in the field of electric vehicles.
However, some serious challenges still need to be overcome before this technology can be transferred to practical application. One of the key issues is the degradation of anode and cathode interfaces. This is still not fully understood and leads to an increase in cell resistance, unwanted additional overvoltage and ultimately to a strong capacity fading.
Within the “BASF International Scientific Network for Electrochemistry and Batteries” our goal is to establish the combination of time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS) for the investigation of lithium-ion-based battery materials. In a recent publication, we have shown that this method combination can provide valuable insights into interfacial degradation in composite cathodes. With ToF-SIMS and XPS we were able to identify degradation products and visualize the formation of the solid electrolyte interface (SEI) layer in a LiNi0.6Co0.2Mn0.2O2/Li6PS5Cl‑composite cathode (abbreviated with NCM and SE in the figure). These results can help to optimize interfaces in composite cathodes, which is essential for the improvement of the long-term cycling stability of ASSBs. This is an important step towards the transition of this new technology to practical application.
Publications: F. Walther et al., Chem. Mater. 2019, Just Accepted Manuscript. DOI: https://doi.org/10.1021/acs.chemmater.9b00770