SnSe quantum dots anchored on few-layered Ti3C2 as anodes for sodium ion batteries with enhanced cycling stability

Metal selenides are considered outstanding potential anodic materials of sodium ion batteries due to their large specific capacity. However, their actual application is heavily restricted because of the unfavorable volume expansion, inferior cycling stability, as well as inactive kinetics. To solve this problem, the structure of SnSe@f-Ti3C2 was rationally designed and synthesized via a simple one-pot solvothermal process for the first time in this work. The high-capacity 0D SnSe quantum dots grow in situ and are characterized as homogeneously distributed on the 2D conductive MXene sheet via the electrostatic attraction of Sn ions and MXene. The SnSe@f-Ti3C2 composite exhibits a remarkably increased capacity of 540 mA h g(-1) at 0.05 A g(-1) and excellent cycle performance of 97.79% retention ratio after 100 cycles at 0.5 A g(-1). The outstanding electrochemical performance of the SnSe@f-Ti3C2 hybrid was mainly attributed to the synergy between 0D SnSe with high capacitance and the 2D MXene sheet with superior conductivity. On one hand, 0D SnSes act as pillars between MXene layers in order to prevent the stacking of MXene nanosheets. On the other hand, the fast electron/ion transport capability and large specific surface area provided by MXene as a conductive skeleton facilitates favorable transfer kinetics as well as close contact in the electrolyte/electrode interface.