In this work, different types of cathode materials for sodium-ion batteries were investigated to identify the suitable material for completing a cell with MXene-type 312 anodes. The research involved both computational analyses to study the structural and ionic transport properties of pure and copper-doped Na_0.44MnO₂ (NMO) materials, as well as experimental data. The experimental goal was to improve the electrochemical performance of NMO while preventing manganese migration into the electrolyte. For this reason, part of the manganese was replaced with Fe, at 45-50%, or with other elements such as Al, Cu, and Si. In these latter cases, the dopant amount did not exceed 10%.

Different synthesis methods were identified to obtain pure materials based on the substituting or doping element. The obtained cathodes were analyzed using potentiodynamic (CV) and galvanostatic (GCPL) tests. The electrochemical performance of NMO was considered improved, as the copper-doped Na_0.44Mn_0.9Cu_0.1O₂ material was able to operate for over 200 GCPL cycles at C/2 without degradation, maintaining a specific capacity above 80 mAh/g. After stabilizing the doped NMO, the focus shifted to identifying high-potential cathode materials to achieve complete cells with higher potential than the NMO-doped/MXene pair.

Attention was directed towards three major families of cathodes: polyanionic, layered-type oxides, and NASICON-structured materials.

Five materials were selected from these three families. For all the chosen materials, the initial focus was on identifying and optimizing the synthesis technique to obtain pure and crystalline samples.

The investigation into high-potential cathodes, which will continue next year, led to the synthesis and structural characterization of five different cathode materials, all obtained with high purity. Electrochemical testing on the fluorophosphate provided very satisfactory results, with specific capacities reaching up to 110 mAh/g at C/10 and 80 mAh/g at 1C, with over 400 charge and discharge cycles.