Monodispersed SnS nanoparticles anchored on carbon nanotubes for high-retention sodium-ion batteries
Sodium-ion batteries (SIB) have been considered alternatives to lithium-ion batteries particularly for grid-scale energy storage owing to the abundance and low cost of Na precursors. While Sn-based anodes offer reasonable theoretical capacity (847 mAh g-1 for Na15Sn4), their sluggish kinetics, low conductivity, and large volume expansion represent unresolved drawbacks. Herein, we report the use of free-standing SnS nanoparticles (in-situ sulfur moieties) anchored on carbon nanotube (CNT) film to obtain high-performance SIB anodes using an effective hydrothermal method. The SnS nanoparticles (less than 10 nm) anchored on CNT film (SnS@CNT) and yield the high capacity of up to 762 mAh g-1 owing to their improved conductivity, which is attributed to the increase in capacity to 146%, compared to the capacity of SnS nanoparticles in the absence of CNT film (521 mAh g-1). The enhancement in the conductivity of the film is attributed to the good distribution of the SnS nanoparticles throughout the CNT network without being aggregated. This stems from the formation of inherent chemical bonds between SnS and the surface of the CNTs. The hybrid film exhibits excellent cyclability at the current density of 1 A g-1, the capacities of 666 and 615 mAh g-1 after 100 (100% retention) and 500 cycles (92% of the initial capacity), respectively, and excellent kinetics. The SnS@CNT hybrid film used as SIB anode contains is binder-free, further adding more active materials for battery performance.