Multilayer Electrodes and Neutrons: A Tool to Study Lithiation Mechanisms

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The electrochemical incorporation and removal of small metal Ions like Li into suitable electrodes is a fundamental process for rechargeable electrochemical energy storage. Consequently, an understanding of the lithiation mechanism of actual high capacity electrodes is of high interest for fundamental and application relevant research. Within this project we will investigate this problem for negative electrodes using a novel approach which is based on multilayer electrodes and in-operando neutron reflectometry. This unique combination allows an easy identification of the fundamental lithiation mechanism and simultaneously a measurement of volume modifications during electrochemical lithiation. The advantage of the approach is that the use of a multilayer arrangement (isotope or chemical modulated) transforms complex neutron reflectivity patterns with numerous interference fringes into a simpler pattern with a single Bragg peak. Hereby, the number of relevant parameters for the description of the pattern will be reduced drastically and an unambiguous interpretation of the results is possible. As multilayer electrode model systems thin films of 73Ge/Ge (isotope) and Si/C (chemical) will be investigated.The electrode material will be produced by ion-beam sputter deposition. Electrode processes should be studied in-operando during galvanostatic cycling and cyclic voltammetry by Neutron Reflectometry. The results should help to fundamentally understand the basic aspects, necessary for an improvement of batteries