Bimetal heterostructure NiCo2Se4 anode confined by carbon nano boxes for ultrafast and stable potassium storage

•The carbon shell can accelerate electron transmission and limit the volume expansion.•Heterogeneous interfaces can accelerate ion transport and enhance reaction kinetics.•The 3D structure and the heterogeneous interface have synergistic effect.•NCS@NC anode exhibits impressive rate performance and cycle stability. Transition metal selenides (TMSes) are regarded as promising anodes for potassium ion batteries (PIBs) benefit from their high theoretical capacity. However, the slow kinetics of potassium ion transport, poor charge transfer ability and short cycle life limit the development of transition metal selenide anode. In this article, the dice-shaped NiCo2Se4@N-doped carbon (NCS@NC) nanocomposite is designed for efficient and stable potassium storage. The in-situ formed carbon shell can not only act as a highly conductive framework to accelerate charge transfer, but also limit the volume fluctuation caused by the potassium ion repeated insertion/ extraction process. The in-situ and ex-situ characterization as well as theoretical calculation show that the heterogeneous interface formed by the heterogeneous metal species in NCS@NC spontaneously establish internal electric fields, which significantly accelerates the ion transport. As results, advanced NCS@NC anode with greatly enhanced electrochemical performance is obtained due to the synergy between the three-dimensional structure design and the heterogeneous interface strategy. NCS@NC anode displays extraordinary rate capacity (471.9 mAh g-1 at 2 A g-1) and ultralong cycle life at high current density (454.5 mAh g-1 at 2 A g-1 after 1000 cycles), which indicates that our modification strategy provides an alternative solution for designing advanced PIBs anodes.