Modified carbons with optimized electrochemical properties as anode material in lithium ion cells

Lithium ion cells are widely used rechargeable batteries for applications in laptops or mobile phones. Purpose of this work is the optimization of the commonly used graphite intercalation anodes. During the first charge/discharge cycles electrolyte decomposition takes place at the anode followed by formation of a film, which hinders further decomposition of the electrolyte. This reaction can be controlled by the surface composition of the anodes. In this work the surface composition and structure of different graphites were changed by gas treatment. Referring to the 'dangling bonds' model, the activated graphite surface with free bonds and adsorption places was treated with a reactive gas. The applicability of the obtained modified graphites as electrode materials was tested in charge/discharge studies. The results were correlated with surface properties of the graphites. For this purpose the specific surface area of the differently treated graphites was determined by BET measurements. The chemical composition and the distribution of the surface groups was measured by electron scanning chemical analysis (ESCA). Optical pictures of the surfaces were obtained by scanning electron microscopy (SEM). (author)