The large-scale implementation of electrochemical energy storage devices requires the development of new materials suited to specific uses. Sodium ion batteries (SIBs) can cover different fields of application, but the most advanced negative material—hard carbon—suffers from poor cyclability and capacity loss. MXenes are a vast class of 2D materials with general formula M_n+1X_nT_x (M=transition metal, X=C or N, T=terminal group) with peculiar structural characteristics capable of reversibly intercalating chemical species, such as alkaline cations. The MXene Ti₃C₂T_x is one of the most studied thanks to its easy preparation by leaching the precursor Ti₃AlC₂. This work studies the effect of leaching conditions and post-synthesis heat treatments on the chemical, morphological and structural properties of Ti₃C₂T_x and, in turn, the correlation between its characteristics and functional properties as negative material in SIBs. The Ti₃C₂T_x obtained in high concentration of HF, after a heat treatment at 300°C, when cycled with a current of 30 mA g^-1 shows 110 mAh g^-1 of capacity with an average potential of 1.33V vs. Na+/Na, and 100% capacity retention. Finally, even when cycled with a current of 1500 mA g^-1 it retains good performance providing a capacity of 73 mAh g^-1 .