In situ selective selenization of ZIF-derived CoSe₂ nanoparticles on NiMn-layered double hydroxide@CuBr₂ heterostructures for high performance supercapacitors

As an emerging energy storage device, the practical application of supercapacitors (SCs) is currently constrained by their low energy density. Enhancing the capacitance of supercapacitors by leveraging the synergistic effect of multiple components in composite electrodes with well-designed structures can effectively increase their energy density. Here, a wire-sheet-particle hierarchical heterostructured CoSe2@NiMn-layered double hydroxide (NiMn-LDH) @Cu1.8Se/Copper foam (CF) electrode is synthesized via phase pseudomorphic transformation process achieved by selective selenization for Cu and Co elements. Benefiting from the stable support structure of CuBr2, the large specific surface area of NiMn-LDH, and the excellent conductivity of CoSe2, the prepared binder-free electrode shows excellent electrochemical properties. The CoSe2@NiMn-LDH@Cu1.8Se hybrid electrode exhibits a superior specific areal capacitance of 7064 mF cm-2 at 2 mA cm-2 and a stable cyclic performance with 80.11 % capacitance retention after 10,000 cycles. Furthermore, the assembled CoSe2@NiMn-LDH@Cu1.8Se/CF//AC (activated carbon) asymmetric supercapacitor (ASC) achieves an energy density of 36.6 Wh kg- 1 when the power density is 760.6 W Kg-1 and retains 87.35 % of the initial capacitance after 5000 cycles. Overall, this pioneering research provided new insight for preparing supercapacitor electrode materials by selective selenization and ration design of the structures.