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. Bimetallic sulfides are regarded as promising electrode materials for potassium ion batteries owing to their attractive theoretical specific capacity, high redox activity, and environmental friendliness. However, undesirable agglomeration and inferior structural reversibility might result in their poor electrochemical performance and block their practical application. In this work, flower-like spherical FeCoS2 coated with reduced graphene oxide was prepared by a one-step hydrothermal synthesis method. As an anode material of potassium ion batteries, this flower-like spherical structure with extensive mesopores is conducive to the rapid penetration of electrolyte, thereby accelerating the transmission of potassium ions. Meanwhile, the encapsulation of reduced graphene oxide not only effectively reduces the structural deformation during the reaction, but also limits the aggregation of FeCoS2, which provides favorable conditions for improving the reversibility of the electrode material. As a result, it exhibits promising cycling stability (maintions 371 mAh g–1 at 100 mA g–1 after 150 cycles) and attractive rate performance (428 mAh g–1 at 50 mA g–1 and 248 mAh g–1 at 1000 mA g–1).