Fabrication of hollow MnFe2O4 nanocubes assembled by CoS2 nanosheets for hybrid supercapacitors

Abstract

Even though the transition metal oxides (TMOs) are theoretically favorable for supercapacitors, the low electrical conductivity and durability hinder their major practical application. Designing TMOs with innovative nanostructures and unique properties is an effective strategy to overcome these limitations and boost their electrochemical properties. Considering this, in this research, we design hollow MnFe2O4 nanocubes assembled by CoS2 nanosheets (designated as HMFO-CSN) and evaluate its supercapacitive performance where it is used as a cathode electrode in the hybrid supercapacitors. The nanostructuring strategy used here includes three steps (i) MnFe-Prussian blue analogue (MnFe-PBA) nanocube formation, (ii) calcination of the MnFe-PBA to produce MnFe2O4 hollow structures, and (iii) growing CoS2 nanosheets on the product through the hydrothermal process to get the final product, i.e., HMFO-CSN. The hollow MnFe2O4 nanocube which acts as the effective skeleton can fasten electron transportation and ion diffusion. Meanwhile, the existing porous CoS2 nanosheet is not only served as an effective outer layer to enhance conductivity but also acts as a structure protector to prevent the collapse and degradation of inner MnFe2O4 hollow nanocube during stability test. Benefiting from such merits, the as-synthesized nanomaterial shows a capacity of 894C g−1 at 1 A g−1 with a rate capability of 76.2% (681.25C g−1 at 48 A g−1), and excellent 90.5% capacity retention at 12 A g−1 after 10,000 cycles. Furthermore, the hybrid supercapacitor made of HMFO-CSN (cathode electrode) and activated carbon (AC, anode electrode) delivers an energy density of 63.75 Wh kg−1 at 850 W kg−1 with high longevity of 88.5% after 10,000 cycles at 12 A g−1. The developed synthetic method may offer new inspirations for the fabrication of high-performance electrode materials with advanced structures for various energy-related applications.