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Ion and Molecule Transport across the Solid Electrolyte Interphase (SEI)

Sketch of a solid electrolyte interface
Figure: Sebastian Kranz

Figure 1: Schematic illustration of (left) electrochemical investigations to determine ion, electron and molecule transport properties and (right) in-situ shell-isolated nanoparticle enhanced Raman spectroscopy for characterizing the chemical composition.

Summary:

Lithium ion batteries (LIBs) are widely used for mobile electronic devices. During the first charging cycle of the battery, the electrolyte (lithium salt in mixture of organic carbonates) decomposes at the graphite anode / electrolyte interface. The decomposition products form the solid electrolyte interphase (SEI), which acts as a passivation layer preventing further electrolyte decomposition. In the ideal case, the SEI is a fast Li+ ion conductor and blocks electrons and molecules completely. However, real SEIs allow for a slow transport of electrons or molecules, which leads to further electrolyte decomposition and slow growing of the SEI. Due to the complex morphology of the SEI, the transport properties are not well understood up to now.

We form SEIs on planar model electrodes by electrochemical means and characterize their chemical composition, morphology and transport properties by combining a number of different experimental techniques (AFM, electron microscopy, shell-isolated nanoparticle enhanced Raman spectroscopy, cyclic voltammetry, electrochemical impedance spectroscopy, redox-probe experiments).

Highlighted Publications:

  • S. Kranz, T. Kranz, A. G. Jaegermann, B. Roling, 'Is the solid electrolyte interphase in lithium-ion batteries really a solid electrolyte? Transport experiments on lithium bis(oxalato)borate-based model interphases', J. Power Sources 418 (2019) 138-146. doi: 10.1016.j.jpowsour.2019.01.060
  • T. Kranz, S. Kranz, V. Miß, J. Schepp, B. Roling, 'Interrelation between Redox Molecule Transport and Li+ Ion Transport across a Model Solid Electrolyte Interphase Grown on a Glassy Carbon Electrode', J. Electrochem. Soc. 164 (2017) A3777-A3784. doi: 10.1149/2.1171714jes