Doping Induced Hierarchical Lattice Expansion of Cobalt Diselenide/Carbon Nanosheet Hybrid for Fast and Stable Sodium Storage

Summary Transition metal chalcogenides have received considerable attention in sodium-ion batteries. However, their practical application is greatly hindered by the low conductivity and sluggish kinetics. Here, we report a hierarchical structure, featuring carbon nanosheets grafted on carbon nanofibers, as a substrate that supports cobalt diselenide (CoSe2@ carbon nanosheets [CNS]/carbon nanofiber [CNF]) to boost the conductivity and prevent electrode pulverization. Moreover, we demonstrate that manganese doping can be used to expand the sodium-ion diffusion channels in Co1-xMnxSe2 and induce the synergistic lattice expansion of carbon nanosheets, alleviating the sluggish kinetics. Exploiting this strategy, the Co1-xMnxSe2@CNS/CNF with pre-sodium treatment can deliver a high specific energy density of 409.4 Wh kg−1 at 0.1 C when paired with Na2V1.85Fe0.15(PO4)3/C cathode in a full cell. This work may provide insights into how doping induces hierarchical lattice expansion of transition metal chalcogenide/carbon hybrids to alleviate sluggish kinetics and enhance sodium storage.