This report summarizes the experimental activities conducted to improve the performance of MXenes to be used as anodes in sodium-ion batteries (NIBs). This objective was pursued both by working on the starting material (MAX phases) and implementing new chemical exfoliation processes and post-etching treatments. The synthesis was optimized through Spark Plasma Sintering of the Ti₂AlC MAX phase and the Ti₃Al_1-xSn_xC₂ solid solution. For both materials the main problems concerned the MXene preparation through the chemical exfoliation process.

As regards the improvement of the electrochemical performance of the Ti₃C₂T_x MXenes, whose preparation process had been optimized in the previous year, new acid solutions were tested for their production starting from Ti₃AlC₂. Furthermore, several post-exfoliation processes in hydrofluoric acid were tested with the aim of modifying the functionalization of the lamellae. The best MXenes were obtained by means of Ti₃C₂T_x heat treatment at 500°C in which a specific organic compound (cetyltrimethylammonium bromide (CTAB)) had previously been inserted among the lamellae.

Furthermore, MXene-based NIB single cells were created and characterized, in which the Na_0.44MnO₂ cathode material is the first generation material developed by RSE in the previous year. NIB devices were assembled in order to check the electrochemical effects of two main parameters: MXene pre-sodiation and active materials weight ratio in the anode and cathode. NIB prototypes provided excellent feedback in terms of specific capacity (≈105 mAh/g of MXene), average potential (between 1.8 and 2.2V) and stability over time. The anode/cathode weight ratio is the most critical aspect to fine-tune in order to maximize performance, also in anticipation of potential industrial developments.