As one of prussian blue analogues,Co3[Co(CN)6]2 has been explored as a promising anode material for potassium-ion batteries (PIBs) owing to its high potassium storage capacity.Unfortunately,Co3[Co(CN)6]2 possesses low electronic conductivity and its structure collapses easily during potassiation and depotassiation,resulting in poor rate performance and cyclic stability.To solve these problems,we develop a facile multi-step method to successfully combine uniform Co3[Co(CN)6]2 nanocubes with rGO by C-O-Co bonds.As expected,these chemcial bonds shorten the distance between Co3[Co(CN)6]2 and rGO to the angstrom meter level,which significantly improve the electronic conductivity of Co3[Co(CN)6]2.Besides,the complete encapsulation of Co3[Co(CN)6]2 nanocubes by rGO endows the structure of Co3[Co(CN)6]2 with high stability,thus withstanding repeated insertion/extraction of potassium-ions without visible morphological and structural changes.Benefiting from the abovementioned structural advantages,the Co3[Co(CN)6]2/rGO nanocomposite exhibits a high reversible capacity of 400.8 mAh g-1 at a current density of 0.1 A g-1,an exceptional rate capability of 115.5 mAh g-1 at 5 A g-1,and an ultralong cycle life of 231.9 mAh g-1 at 0.1 A g-1 after 1000 cycles.Additionally,the effects of different amounts of rGO and different sizes of Co3[Co(CN)6]2 nanocubes on the potassium storage performance are also studied.This work offers an ideal route to significantly enhance the electrochemical properties of prussian blue analogues.