Multi-layered heterogeneous interfaces created in Co0.85Se@Ni3S4/NF to enhance supercapacitor performances by multi-step alternating electrodeposition†

Heterogeneous interface construction is of far-reaching significance to optimize the electrochemical performance of electrodes. Herein, a multi-step alternating electrochemical deposition (MAED) method is proposed to alternately deposit Co_0.85Se and Ni₃S₄ nanosheets on a nickel foam (NF), forming a special alternate layer-by-layer structure with multi-layered heterogeneous interfaces. The creation of the multi-layered heterogeneous interfaces provides a large interfacial area for redox reactions with optimum interstitials facilitating ion diffusion, thus greatly improving the electrochemical energy storage efficiency. With the increase in the layer number, the material exhibits increasingly better energy storage performance, and 8L-Co_0.85Se@Ni₃S₄/NF exhibits the highest specific capacitances of 2508 F g⁻¹ and 1558 F g⁻¹ at a scan rate of 2 mV s⁻¹ and a current density of 1 A g⁻¹. The 8L-Co_0.85Se@Ni₃S₄/NF//polypyrrole (PPy)/NF asymmetric supercapacitor provides a maximum operation potential window of 1.55 V and energy densities of 76.98 and 35.74 W h kg⁻¹ when the power densities are 775.0 and 15 500 W kg⁻¹, respectively, superior to most of the related materials reported. Through MAED, the deposited phase and the layer number can be accurately controlled, thus providing an efficient strategy for interface construction so as to increase the electrochemical activity of the energy storage materials.