Molecular Coupling and Self-Assembly Strategy toward WSe2 /Carbon Micro-Nano Hierarchical Structure for Elevated Sodium-Ion Storage.

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Sodium (Na) ion-based dual-ion batteries (Na-DIBs) have attracted great attention, owing to their benefits of low cost, high working voltage, and environmental friendliness. However, the limited capacity and low tap density of currently reported anode materials restrict the further improvement of Na-DIBs. Herein, a micro-nano structure with vertically aligned WSe2 nanoflakes anchored tightly on a micron-sized carbon sphere (WSe2 /CS) is successfully constructed via combining the molecular coupling and self-assembly strategy. Within this hierarchical structure, the WSe2 nanoflakes can shorten the diffusion path for Na+ ions and alleviate structural deformation during the charge/discharge process; meanwhile, the micron-sized carbon core provides conductive support and helps improve the total tap density of the anode electrode. As a result, this micron-sized WSe2 /CS displays a high specific capacity of ≈252.8mAhg-1 and good cycling performance with ≈92% capacity retention after 1200 cycles. Moreover, by pairing this WSe2 /CS anode with environmental friendly graphite as cathode, a proof-of-concept Na-DIB shows 85.6% capacity retention after 1000 cycles, which is among the best performances of previously reported Na-DIBs.