Core-shell heterostructured FeCo2O4@NiMn-layered double hydroxide on nickel foam as electrode materials for high performance supercapacitors

Abstract

Layered double hydroxides (LDHs) are promising pseudocapacitor electrode materials due to their high theoretical capacity and tunable composition. However, their poor rate capability and limited cycling stability hinder practical applications. Herein, the FeCo₂O₄@NiMn-LDH core-shell heterostructures are grown in situ on nickel foam via electrodeposition, annealing, and hydrothermal processes. The uniformly coated FeCo₂O₄ nanosheets eliminate the usage of binders and ensure the excellent electronic transport properties of the nickel foam. The grown NiMn-LDHs on these nanosheets forms a porous mesh with high specific surface area and abundant active sites. This unique structure enhances electrolyte accessibility, redox kinetics, and volume change accommodation, resulting in superior rate capability and cycling stability. The optimal FeCo₂O₄@NiMn-LDH-2 exhibits a specific capacitance of 1502 F g⁻¹ at 1 A g⁻¹, 74.6 % capacitance retention at 20 A g⁻¹, and 88.33 % retention after 5000 cycles. The assembled asymmetric supercapacitor FeCo₂O₄@NiMn-LDH//activated carbon achieves an energy density of 45.42 Wh·kg⁻¹ at 750 W kg⁻¹, with 89.2 % capacitance retention after 5000 cycles. This work provides a rational design strategy for high-performance LDH-based supercapacitor electrodes.