Reduced graphene oxide coated modified SnO2 forms excellent potassium storage properties.

In this work, SnO 2 and Sn nanoparticles adhered to the surface of rGO (SnO 2 /Sn/rGO) applied as potassium ion batteries (KIBs) anode materials were synthesized via thermal reduction. Preparing SnO 2 material into a nanostructure for modification can reduce ion diffusion distance to improve the number of active sites appropriate for K+ adsorption, and efficiently reduce the volume change which is conducive to enhancing the potassium storage capacity. Besides, layered rGO inhibits SnO 2 /Sn aggregation, while increased surface area also reduces diffusion channel and electrolyte contact. However, larger specific surface area result in a lower initial Coulomb efficiency (ICE). The approach adopted here is to force the solid electrolyte interface (SEI) to fully emerge during the first charge-discharge cycle by using electrolytes containing 1 M KFSI in EC and DEC (1:1, v/v). According to density functional theory (DFT) analysis, the doping of rGO and SnO2 effectively enhanced the adsorption of potassium atoms and reduced the diffusion barrier of K+. Therefore, SnO 2 /Sn/rGO nanocomposites have a high specific capacity (325.8 mAhg−1 after 350 cycles at 0.1 Ag-1), an excellent ICE (66.57%), and a long cycle life (203.6 mAhg−1 after 1000 cycles at 0.5 Ag-1). [ABSTRACT FROM AUTHOR]