Well-defined hollow tube@sheets NiCo2S4 core–shell nanoarrays for ultrahigh capacitance supercapacitor

The well-defined hollow tube@sheet NiCo 2 S 4 core–shell nanoarrays are rationally constructed to the free-standing electrode and exhibit excellent areal capacitance of 11.3 F cm −2 at a current density of 2 mA cm −2 .