Oxidized Ti3Al(1-x)SnxC2 MAX phases as negative electrode materials for sodium ion batteries

Materials proposed for the negative electrodes in sodium-ion batteries often include oxides capable of reacting with Na+ through intercalation, conversion, or alloying. While these oxides offer high specific capacities, they suffer from poor mechanical stability. A novel approach to address this issue involves designing tailored nanocomposites based on the (Ti/Sn)Ox system, achieved through partial oxidation of tin-containing MAX phase (Ti3Al(1-x)SnxC2, x = 0.4 and 0.7). By employing this strategy, we have developed composite electrodes based on Ti(1-y)SnyO2 and MAX phase, which exhibit remarkable durability, withstanding over 600 cycles in half-cells. These electrodes also demonstrate charge efficiencies higher than 99.8 % and specific capacities comparable to MXenes electrodes. These outstanding electrochemical performances are further validated at the full-cell level when combined with Na0.44MnO2 positive electrodes. The reaction mechanism between the composite and the sodium ion was also studied using in-situ techniques (Raman and XAS) and the contribution of the different components during sodiation and de-sodiation was highlighted.