MobilNachhaltigTC Plattling MoMo
E. dos Santos Sardinha, Michael Sternad, H. Wilkening, H. Martin, G. Wittstock
Nascent SEI-Surface Films on Single Crystalline Silicon Investigated by Scanning Electrochemical Microscopy
ACS Applied Energy Materials, vol. 2, no. 2, pp. 1388-1392
Silicon is a promising high-capacity host material for negative electrodes in lithium-ion batteries with low potential for the lithiation/delithiation reaction that is outside the stability window of organic carbonate electrolytes. Thus, the use of such electrodes critically depends on the formation of a protective solid electrolyte interphase (SEI) from the decomposition products of electrolyte components. Due to the large volume change upon charging, exposure of the electrode material to the electrolyte must be expected, and facile reformation of SEI is a scope for improving the stabilities of such electrodes. Here, we report the formation of incipient SEI layers on monocrystalline silicon by in situ imaging of their passivating properties using scanning electrochemical microscopy after potentiodynamic charging to different final potentials. The images show a local initiation of the SEI growth at potentials of around 1.0 V vs Li/Li+ in 1 M LiClO4 in propylene carbonate.
Maschinenbau und Mechatronik
Thomas Petersmeier, U. Martin, D. Eifler, H. Oettel
Cyclic fatigue loading and characterization of dislocation evolution in the ferritic steel X22CrMoV121
International Journal of Fatigue, vol. 20, no. 3
Isothermal cyclic deformation tests have been performed with the steel X22CrMoV121 in the temperature range 20°C ⩽ T ⩽ 600°C. The fatigue behaviour was related to microstructural changes in the bulk material. The dislocation density was determined for selected fatigue states by means of transmission electron microscopy. The material is characterized by cyclic softening in the investigated temperature range. Increasing temperatures and increasing stress amplitudes lead to an increase of the plastic strain amplitudes and a corresponding reduction of the number of cycles to failure. In the temperature range 250°C ⩽ T ⩽ 350°C dynamic strain ageing processes occur and maximum dislocation densities are observed. Generally the dislocation density decreases with increasing number of cycles and temperatures.