Ultrasmall-sized SnS nanosheets vertically aligned on carbon microtubes for sodium-ion capacitors with high energy density

Sodium ion hybrid capacitors (SHCs) using battery-type and capacitor-type electrodes are designed to obtain both high energy and power densities. However, anode materials commonly cannot meet the high capacity and rapid charging/discharging stability requirements. With the help of sandwiched design, herein novel porous carbon microtubes are sandwiched by vertical ultrasmall-sized SnS nanosheets (SnS/aCMT) via combined solvothermal and thermal-treatment approaches. The three-dimensional interconnected SnS nanosheet network grown on both sides of the hollow carbon microtubes could greatly prevent their aggregation and facilitate ion transport, which endows the anode material with improved specific capacity and structural stability. As a result, the SnS/aCMT electrode presents high capacity (517 mA h g−1 at 0.1 A g−1) and remarkable rate capability (306 mA h g−1 even at 5 A g−1) as well as long-term cycling stability with 88.7% retention over 500 cycles. Furthermore, a SHC, assembled by using SnS/aCMT as the anode and aCMT as the cathode, presents a high energy density of 115 W h kg−1 in the voltage range of 0.5–4.0 V and stable long-term cycling performance.