A novel sea-sponge structured C/SnS@C nanocomposite exhibits excellent cyclability over 2000 cycles as sodium-ion batteries.

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Development of highly stabile battery-type electrode materials with superior capacity has been a critical challenge for hybrid supercapacitors. We report a high-performance electrode material, tubular sandwich-structured CNT@Ni@Ni 2 (CO 3 )(OH) 2 , synthesized via a scalable, dynamic, controlled in situ reduction− chemical deposition process. Applied as a battery-type electrode material, this novel nanostructure exhibits excellent electrochemical stability, majorly attributed to the Ni midshell serving a dual role as "capacity supplement" and "electron highway", which, to our knowledge, was incorporated into the nanocomposite electrodes for the first time. Also benefiting from the high conductivity of carbon nanotubes (CNTs) and the high capacity of the amorphous NiOOH ultrathin film [converted from the Ni 2 (CO 3 )(OH) 2 outer shell], the resulting CNT@Ni@Ni 2 (CO 3 )(OH) 2 material as a battery-type electrode achieves a superior capacity of 221 mAh•g −1 at 5 A•g −1 with 76% capacity retention at 50 A•g −1 and maintains 81% capacity after 9000 cycles at 5 A•g −1 . An advanced aqueous hybrid supercapacitor using activated carbon and CNT@Ni@Ni 2 (CO 3 )(OH) 2 nanocomposite as the negative and positive electrodes, respectively, delivers a high energy density of 179 Wh•kg −1 at a power density of 2880 W•kg −1 with capacitance retention in excess of 85% over 5500 cycles. The outstanding performance demonstrates its practical potential in advanced hybrid supercapacitors.

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