Flower-like spherical FeCoS2 coated by reduced graphene oxide as anode for high performance potassium ion storage

•The flower-like spherical FeCoS2@rGO was successfully prepared by a one-step hydrothermal method.•The electrostatic attraction between FeCoS2 and reduced graphene oxide produced an effective and dense protective layer.•The unique structure can increase the contact area with electrolyte and thus promote the rapid penetration of electrolyte.•The FeCoS2@rGO shows a high capacity and good rate capability as a promising anode material for PIBs.