Novel hierarchical CoFe2Se4@CoFe2O4 and CoFe2S4@CoFe2O4 core-shell nanoboxes electrode for high-performance electrochemical energy storage

The novel structure of electrode materials with high conductivity, large specific surface area and ultra-high energy density is urgently needed to achieve high performance energy storage. Here, a novel hierarchical CoFe2Se4@CoFe2O4 and CoFe2S4@CoFe2O4 core-shell nanoboxes electrode arrays with uniform size and morphology have been successfully deposited on nickel foam through a mild two-step hydrothermal method, which have been further developed as binder-free electrode materials for asymmetric supercapacitors, because of the core-shell structural advantage and multifunctionality of the CoFe2Se4@CoFe2O4 and CoFe2S4@CoFe2O4 nanoboxes. Moreover, the CoFe2Se4@CoFe2O4 electrode acquires an exceptional specific capacitance of 2040.8 F g−1 at 1 A g−1 and excellent rate performance, which is superior to other ternary transition metal sulfides. An asymmetric device with carbon nanotubes as negative electrode, CoFe2Se4@CoFe2O4 as positive electrode and 3 M KOH as electrolyte also demonstrates a wide voltage of 1.6 V, a desirable specific capacitance (463.27 F g−1 at 1 A g−1), and a higher energy density of 164.72 Wh kg−1 (at 508 W kg−1) than other reports. Meanwhile, the CoFe2Se4@CoFe2O4//CNTs asymmetric supercapacitor can drive the toy car more than 15 m, indicating the CoFe2Se4@CoFe2O4 electrode own powerful energy storage capacity and application value.