Investigation of SnS -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, SnS is attractive due to the competitively high specific capacity, low redox potential and high abundance. Porous few-layer SnS nanosheets are in situ grown on reduced graphene oxide, forming a SnS -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 SnS -rGO. This work explores the influence of different conductive carbons (Super P and C65) on the SnS -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.