Manipulating the Polytellurides of Metallic Telluride for Ultra‐Stable Potassium‐Ion Storage: A Case Study of Carbon‐Confined CoTe2 Nanofibers

Abstract Transition metal tellurides (TMTes) are promising anode materials for high energy density potassium‐ion batteries (PIBs) due to their high electronic conductivity and high theoretical volumetric capacity. Most reported TMTes electrodes have limited lifespans, however, in this work, for the first time, it is revealed that the dissolution and shuttling effect of polytellurides (K 5 Te 3 and K 2 Te) are the key reasons for the rapid deterioration of cycling stability in TMTe‐based conversion‐ and alloy‐type anodes. In light of this, a dual‐type N‐doped carbon‐confined CoTe 2 composite material (CoTe 2 @NPCNFs@NC, where NPCNFs stands for N‐doped porous carbon nanofibers and NC represents N‐doped porous carbon) is proposed to suppress the dissolution and shuttle effect of polytellurides, which boosts the cycling stability up to 1000 cycles at 2 A g −1 . Furthermore, various in situ and ex situ techniques and theoretical calculations are employed to systematically clarify the formation and transformation of polytellurides and to reveal the good physical confinement of the dual‐type carbon and the strong chemisorption of pyridinic‐N and pyrrolic‐N on K 5 Te 3 and K 2 Te. This work highlights the important role of manipulating polytelluride in the design of long‐lifespan TMTe anodes for advanced PIBs.