Engineering conductive carbon networks within hollow structure: A wire-in-tube Co9S8/C@C composite for efficient K-ion storage

[Display omitted] •A wire-in-tube Co9S8/C@C composite is constructed to realize fast and stable potassium storage performance.•The rate capability of WIT Co9S8/C@C composite outperforms most cobalt sulfide-based anodes reported so far for PIBs.•The internal carbon network engineering of WIT structure results in superior structural integrity and fast charge transportation. Hollow structured composites show great promising to accommodate the large volume fluctuation of high-capacity anodes with good structure integrity, while it still suffers from insufficient charge transportation due to the intrinsic low conductivity of anodes and the limited transport channels within hollow structure. Herein, conductive carbon networks are rationally constructed within hollow structure to realize both excellent structure stability and superior charge transportation. By encapsulating MOF-derived Co9S8/C wires into hollow carbon tubes, as-prepared wire-in-tube (WIT) Co9S8//C@C composite manifests exceptional potassium storage performance. It displays excellent cycling retention and maintains high capacities of 410 mA h g−1 at 100th cycle under 0.1 A/g and 201 mA h g−1 after 1500 cycles at 1 A/g. It also achieves a superior rate capability of 200 mA h g−1 at 10 A/g, surpassing most cobalt sulfide-based anodes that have been reported for PIBs. As revealed by in-depth characterizations and theoretical calculation, the conductive network engineering within hollow structure can optimally augment the electron/ion conductivity of Co9S8 and tolerate its volume changes during cycles, thus leading to the exceptional performance of WIT Co9S8//C@C composite.