The MeLuBatt consortium investigated porous carbon xerogel gas diffusion electrodes (GDEs) for lithium‑oxygen batteries, focusing on how pore size, wettability, and operating conditions influence discharge capacity, cycle life, and depth of utilization. IFAM fabricated xerogel GDEs with standard pore diameters of 25–29 nm and a larger 38 nm variant. When tested in full cells at the University of Giessen, the 38 nm GDEs delivered markedly higher capacities at comparable current densities. For example, at 500 µA cm⁻² the discharge capacity nearly doubled when the electrode was wetted for a longer period, and at 1500 µA cm⁻² significant capacities were still achieved. Cross‑sectional imaging revealed that higher current densities promoted deeper deposition of Li₂O₂ within the GDE, allowing more efficient use of the electrode volume. These observations suggest that larger mesopores improve ionic pathways and expose more electrochemically active surface.

Full‑cell cycling experiments (Work Package 6) explored both capacity‑limited and voltage‑limited protocols. With a capacity limit of 5 mAh g⁻¹ and a current density of 100 µA cm⁻², the cells completed 100 cycles without measurable capacity loss. When the capacity limit was increased fourfold, 50 stable cycles were obtained. In voltage‑limited tests at 1500 µA cm⁻², a protected lithium anode enabled the cells to retain more than 5 mAh g⁻¹ after 100 cycles; after about 30 cycles the capacity had fallen to roughly half its initial value. These results demonstrate that cycle stability depends strongly on pore size, wettability, and the presence of hold times between discharge and charge steps. The data also indicate that high current densities alter the morphology of the discharge product, requiring an optimal balance between GDE volume and depth of utilization to achieve superior performance.

The project’s scientific milestones were met: the porous carbon xerogel GDE was successfully processed and integrated into Li/O₂ cells, and its performance was evaluated in full‑cell configurations. The consortium’s work was supported by German federal funding, with a budget of approximately €306 k for personnel, €4.5 k for travel, €3.6 k for materials, and €9 k for investment equipment. The funding covered the high technical and scientific effort required to address the inherent risks of metal‑air battery development.

Collaboration involved several German research institutions. IFAM led the design and synthesis of the xerogel GDEs. The University of Giessen performed the electrochemical testing and provided data on wettability and pore size effects. TU Berlin contributed simulation work (Work Package 5) to model system behavior, while ZSW supplied electrolytes. The Fraunhofer Institute for Applied Materials and Interfaces (FZJ) and the Institute for Energy Conversion (MEET) supplied metal anodes. The consortium coordinated through regular meetings and conferences, and a joint review article is in preparation to disseminate the findings to the broader scientific community. Two peer‑reviewed papers have already appeared, and the project’s outcomes have spurred additional metal‑air battery initiatives and a small‑enterprise funding program focused on zinc‑air technology for seawater treatment.