Kohlenstoff Xerogele als Kathodenmaterial für die aprotische Lithium/Sauerstoff Batterie : Einfluss der Porenstruktur auf die physikalischen und elektrochemischen Eigenschaften

In this work the influence of the pore structure of the GDE on the discharge reaction od the aprotic Lithium-oxygen battery has been investigated. Therefore, carbon xerogels with different pore sizes were synthesized and analyzed by nitrogen adsorption. The samples with the highest and lowest mesopore size have been chosen to investigate the wetting behavior of solvents on the pore walls. Nuclear magnetic resonance (NMR) measurements were conducted to resolve the liquid phase inside of the porous structure. To use the carbon xerogels as active material in the GDE they were directly synthesized in a carbon fiber paper. The resulting ready-to-use and binder-free cathodes were discharged in the lithium/oxygen system and the deposition of discharge products was investigated. Electrochemical impedance measurements were conducted to observe the changes at the cathode during discharge revealing that the charge transfer between the carbon surface and the oxygen stays nearly constant. On the other hand it was also found that the pore clogging with discharge product and consequently the hindered oxygen diffusion are the limiting processes in this type of GDE.