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

Abstract

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.

Keywords: batteries; fluoroethylene carbonate; potassium; sandwich structure; sodium.