In situ selective selenization of ZIF-derived CoSe nanoparticles on NiMn-layered double hydroxide@CuBr 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 CoSe@NiMn-layered double hydroxide (NiMn-LDH) @CuSe/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 CuBr, the large specific surface area of NiMn-LDH, and the excellent conductivity of CoSe, the prepared binder-free electrode shows excellent electrochemical properties. The CoSe@NiMn-LDH@CuSe hybrid electrode exhibits a superior specific areal capacitance of 7064 mF cm at 2 mA cm and a stable cyclic performance with 80.11 % capacitance retention after 10,000 cycles. Furthermore, the assembled CoSe@NiMn-LDH@CuSe/CF//AC (activated carbon) asymmetric supercapacitor (ASC) achieves an energy density of 36.6 Wh kg when the power density is 760.6 W Kg 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.