Synergetic Effect of Binary ZnS:SnS Composites with Reduced Graphene Oxide and Carbon Nanotubes as Anodes for Sodium-Ion Batteries

The development of innovative materials with excellent electrochemical properties is immediately needed to dispel the problems of battery performance. In the present study, the hydrothermal method was applied to synthesize bimetallic sulfides (ZnS:SnS), which were then anchored on reduced graphene oxide (rGO) to produce ZnS:SnS@rGO composites or combined with carbon nanotubes (CNTs) to achieve ZnS:SnS@CNT composites. These composites were then investigated as electrodes for sodium-ion batteries, and their charge storage properties were analyzed. Nanostructures and the morphology of the as-prepared composites were examined by X-ray diffraction, scanning or transmission electron microscopy, and X-ray photoelectron spectroscopy. The specific charge capacity for the ZnS:SnS@CNT composite reaches 364 mA h g–1, while the ZnS:SnS@rGO composite shows 343 mA h g–1 at 0.1 C. Moreover, the inclusion of the conductive matrices also stabilizes the cycle life and rate capability even up to 5.0 C. Nyquist plots obtained as a result of impedance spectroscopy illustrate that the ZnS:SnS@CNT composite electrodes enable fast charge transfer due to lower charge transfer resistance of 44.4 Ω as compared to ZnS:SnS@rGO (i.e., 51.5 Ω) and bare ZnS:SnS (i.e., 68 Ω) electrodes. Electrochemical analysis proves that the presence of dual metal-sulfide ions combined with reduced graphene or CNTs as a conductive matrix results in considerably improved ion storage properties owing to the enhanced electronic conductivity, cushioned volume expansion, and provision of ionic transport highways through the electrode.