Fe₃O₄ Nanoparticles Coated with Ni/Mn-Layered Double Hydroxide Nanosheets as Supercapacitor Materials

NiMn-LDH has been identified as a promising electrode material for supercapacitors, but its performance is constrained by limitations of conductivity and stability. Herein, we present a method for enhancing the performance of the NiMn-LDH electrode through the construction of a Fe 3 O 4 @NiMn-LDH core–shell heterostructure. Strong interfacial interactions between Fe 3 O 4 nanoparticles, which act as conductive cores, and the NiMn-LDH nanosheet shell lower the metal valence states and increase the capacity. Moreover, Fe 3 O 4 nanoparticles weaken the oxidation process of the Mn element and reduce the Jahn–Teller effect while preventing the agglomeration of NiMn-LDH and buffering the volume change. Therefore, Fe 3 O 4 -18@NiMn-LDH has good conductivity, electrochemical performance, and stability. Fe 3 O 4 -18@NiMn-LDH exhibits a high specific capacity of 2120 F g –1 at 1 A g –1 . In situ Raman spectroscopy shows that the mutual transformation of (Ni,Mn)(OH) 2 and (Ni,Mn)OOH is the chemical change that occurs during charge–discharge. The device composed of Fe 3 O 4 -18@NiMn-LDH and activated carbon provides 56.47 W h kg –1 energy density at 800 W kg –1 and retains 92.80% initial capacity after 10,000 cycles at 10 A g –1 . This work provides ideas for enhancing the electrochemical properties of NiMn-based electrode materials and promotes the application of core–shell heterostructure materials in energy storage.