The high specific energy density of the Li-oxygen battery makes the system an extremely attractive and intensively investigated technology for storing electricity in the future. Central challenges in materials science lie in the electrochemical stability of the electrolyte against the reactive oxygen species and against Li metal, the dendrite-free cyclization of the Li-based structured anode, the provision of a gas diffusion electrode (GDE) with a suitable pore structure, wetting behavior, and electrochemical stability.
The gas diffusion electrode (GDE) cathode is the limiting factor for the achievable energy densities. Due to the formation of the solid discharge product lithium peroxide (Li2O2) the porosity of the GDE needs to be chosen in the since of highly available surface area for depositing the solid discharge product. Also, the porosity changes during operation, as does its electrical conductivity. In addition, the carbon substrate usually used in the GDE reacts with the discharge products during the charging process. Titanium carbide (TiC)-based gas diffusion electrodes offer good electrical properties and electrochemical stability. Therefore, nano-TiC material is chosen to develop a porous active layer of the GDE for high-performance and stable operation in Li/Air cells. Moreover, the general requirements for a good performing GDE are good oxygen diffusion for oxygen supply, large interface AL/electrolyte as reaction area and large interface oxygen/electrolyte and O2 dissolution within electrolyte. The GDEs are produced by means of spray coating, whereby nanoscale titanium carbide powder is applied as an active layer on a gas distribution substrate. For determination of the morphology and surface quality high resolution scanning electron microscope (SEM) analysis has been carried out which shows a homogeneous distributed active layer thickness with a porous structure. With galvanostatic discharge and electrochemical impedance spectroscopy the relationship between electrolyte wetting time of the GDE and the maximum achieved capacity were analyzed.