Defect-induced electron rich nanodomains in CoSe0.5S1.5/GA realize fast ion migration kinetics as sodium-ion capacitor anode

Optimizing charge migration and alleviating volume expansion in anode materials are the key to improve the electrochemical performance for sodium-ion storage devices. Herein, a hierarchical porous conducting matrix confining defect-rich selenium doped cobalt dichalcogenide (CoSe_0.5S_1.5/GA) is constructed as a promising SICs anode based on the guidance of theoretical calculation analysis. The increased defect concentration significantly enhanced the disorder degree of the compound and presented electron aggregation around the S atoms, which effectively modulated the electronic structure, further enabling high rate and ultra-capacity sodium storage. Moreover, strong interfacial coupling could construct spatial constraint to alleviate volume expansion as well as maintain electrode integrity and stability. The CoSe_0.5S_1.5/GA electrode can deliver a high capacity of 310.1 mA h g⁻¹ after 2000 cycles at 1 A g⁻¹, and the CoSe_0.5S_1.5/GA//AC sodium ion capacitor can exhibit an outstanding energy density of 237.5 W h kg⁻¹. A series of characterization and theoretical calculation convincingly reveal that the defect moieties can regulate the Na⁺ storage and diffusion kinetics, which prove that our defect manufacture coupling with space-confined strategy can provide deep insights into the development of high-performance Na⁺ storage devices.