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Research Topic:
  Investigation of the charge storage mechanism of Si thin film.
Martin Pradel

A relevant aspect of the silicon based anode research is to characterize the Li charging mechanisms and the density distribution of the charge storage element at the anode interface. Particularly as Si thin films emphasized the surface chemistry rather than the material bulk properties. Dedicated to this specific research, our group has developed a model anode which is composed of multiple nano-metric thin film layers of material deposited in a single batch process by a dedicated LP-CVD reactor. Figure 1a shows a TEM image of such model electrode cross section where a low roughness Ti disc is used as current collector and silicon is deposited on a blocking layer formed of TiN that avoids the formation of silicides. This is supported by an elemental mapping of Si (Figure 1b) and Ti (Figure 1c) of the anode cross section that demonstrates the efficiency of TiN to inhibit the formation of silicides. In agreement with literature, we have demonstrated that the mechanical degradation process is vanishing bellow a Si critical characteristic size of ca. 100-150 nm. Current research investigates the relationship between the Si surface chemical alteration, through chemical functionalization or doping, and its influence on the electro-chemical stability and dynamics. A part of this investigation is devoted to the development of in-situ spectroscopic characterization methods of the electrode interface. This research contributes to a better fundamental understanding of the stability limiting mechanisms related to the interface chemistry and outline new routes for the improvement of the cycling stability of silicon based anodes.


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