Toward Understanding the Enhanced Pseudocapacitive Storage in 3D SnS/MXene Architectures Enabled by Engineered...

The optimization of three-dimensional (3D) MXene-based electrodes with desired electrochemical performances is highly demanded. Here, a precursor-guided strategy is reported for fabricating the 3D SnS/MXene architecture with tiny SnS nanocrystals (≈5 nm in size) covalently decorated on the wrinkled Ti₃ C₂ T_x nanosheets through Ti-S bonds (denoted as SnS/Ti₃ C₂ T_x -O). The formation of Ti-S bonds between SnS and Ti₃ C₂ T_x was confirmed by extended X-ray absorption fine structure (EXAFS). Rather than bulky SnS plates decorated on Ti₃ C₂ T_x (SnS/Ti₃ C₂ T_x -H) by one-step hydrothermal sulfidation followed by post annealing, this SnS/Ti₃ C₂ T_x -O presents size-dependent structural and dynamic properties. The as-formed 3D hierarchical structure can provide short ion-diffusion pathways and electron transport distances because of the more accessible surface sites. In addition, benefiting from the tiny SnS nanocrystals that can effectively improve Na⁺ diffusion and suppress structural variation upon charge/discharge processes, the as-obtained SnS/Ti₃ C₂ T_x -O can generate pseudocapacitance-dominated storage behavior enabled by engineered surface reactions. As predicted, this electrode exhibits an enhanced Na storage capacity of 565 mAh g^-1 at 0.1 A g^-1 after 75 cycles, outperforming SnS/Ti₃ C₂ T_x -H (336 mAh g^-1 ), SnS (212 mAh g^-1 ), and Ti₃ C₂ T_x (104 mAh g^-1 ) electrodes.