Investigation of SnS2-rGO Sandwich Structures as Negative Electrode for Sodium-Ion and Potassium-Ion Batteries

Sodium-ion and potassium-ion batteries (NIBs and KIBs) are considered promising alternatives to replace lithium-ion batteries (LIBs) in energy storage applications due to the natural abundance and low cost of Na and K. Nevertheless, a critical challenge is that the large size of Na+/K+ leads to a huge volume change of the hosting material during electrochemical cycling, resulting in rapid capacity decay. Among negative candidates for alkali-metal-ion batteries, SnS2 is attractive due to the competitively high specific capacity, low redox potential and high abundance. Porous few-layer SnS2 nanosheets are in situ grown on reduced graphene oxide, forming a SnS2-rGO sandwich structure via strong C-O-Sn bonds. This nano-scaled sandwich structure not only shortens Na+/K+ and electron transport pathways but also accommodates volume expansion, thereby enabling high and stable electrochemical cycling performance of SnS2-rGO. This work explores the influence of different conductive carbons (Super P and C65) on the SnS2-rGO electrode. In addition, the effects of the electrolyte additive fluoroethylene carbonate (FEC) on the electrochemical performance in NIBs and KIBs is evaluated. This work provides guidelines for optimized electrode structure design, electrolyte additives and carbon additives for the realization of better NIBs and KIBs.

Automated summary

Sodium-ion and potassium-ion batteries are potential alternatives to lithium-ion batteries in energy storage, with advantages of abundance and low cost of Na and K. However, the large size of Na+/K+ causes volume change of the hosting material, resulting in capacity decay. In this study, porous few-layer SnS2 nanosheets are grown on reduced graphene oxide, forming a SnS2-rGO sandwich structure. This nanostructure enables high and stable electrochemical cycling performance of SnS2-rGO. The effects of different conductive carbons and electrolyte additive on the electrochemical performance are also evaluated. This work provides guidelines for better NIBs and KIBs through optimized electrode structure, electrolyte additives, and carbon additives.