Soft-Rigid Heterostructures with Functional Cation Vacancies for Fast-Charging and High-Capacity Sodium Storage.
basic_science · Level V
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- Also identified by DOI 10.1002/adma.202305149.
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Abstract
Optimizing charge transfer and alleviating volume expansion in electrode materials are critical to maximize electrochemical performance for energy-storage systems. Herein, an atomically thin soft-rigid Co<sub>9</sub> S<sub>8</sub> @MoS<sub>2</sub> core-shell heterostructure with dual cation vacancies at the atomic interface is constructed as a promising anode for high-performance sodium-ion batteries. The dual cation vacancies involving V<sub>Co</sub> and V<sub>Mo</sub> in the heterostructure and the soft MoS<sub>2</sub> shell afford ionic pathways for rapid charge transfer, as well as the rigid Co<sub>9</sub> S<sub>8</sub> core acting as the dominant active component and resisting structural deformation during charge-discharge. Electrochemical testing and theoretical calculations demonstrate both excellent Na<sup>+</sup> -transfer kinetics and pseudocapacitive behavior. Consequently, the soft-rigid heterostructure delivers extraordinary sodium-storage performance (389.7 mA h g<sup>-1</sup> after 500 cycles at 5.0 A g<sup>-1</sup> ), superior to those of the single-phase counterparts: the assembled Na<sub>3</sub> V<sub>2</sub> (PO<sub>4</sub> )<sub>3</sub> ||d-Co<sub>9</sub> S<sub>8</sub> @MoS<sub>2</sub> /S-Gr full cell achieves an energy density of 235.5 Wh kg<sup>-1</sup> at 0.5 C. This finding opens up a unique strategy of soft-rigid heterostructure and broadens the horizons of material design in energy storage and conversion.