In Situ Mechanical Analysis of the Nanoscopic Solid Electrolyte Interphase on Anodes of Li-Ion Batteries

The interfacial decomposition products forming the so-called solid-electrolyte interphase (SEI) significantly determine the destiny of a Li-ion battery. Ultimate knowledge of its detailed behavior and better control are required for higher rates, longer life-time, and increased safety. Employing an electrochemical surface force apparatus, it is possible to control the growth and to investigate the mechanical properties of an SEI in a lithium-ion battery environment. This new approach is here introduced on a gold model system and reveals a compressible film at all stages of SEI growth. The demonstrated methodology provides a unique tool for analyzing electrochemical battery interfaces, in particular in view of alternative electrolyte formulations and artificial interfaces. B.M. acknowledges travel support by InnoEnergy Ph.D. School. The authors thank Carsten Dosche for additional XPS support. Furthermore, the funding of the Escalab250 Xi XPS spectrometer at Carl von Ossietzky University of Oldenburg by the Deutsche Forschungsgemeinschaft (INST 184/106-1 FUGG and INST 184/144-1 FUGG) is acknowledged. B.M. and H.W.C. performed the SFA experiments. C.M. and Q.H. helped with the experiments and produced thin films. B.M., Q.H., and M.O. provided XPS measurements. M.V. and F.U.R. conceived and designed the experiments. M.S. designed and carried out theoretical kinetic analysis. All authors analyzed data, discussed the results, co-wrote the paper, and commented on the manuscript.