In-situ electrochemical preparation of MnOx/CC with porous structure and mixed valence for supercapacitor

Abstract

Manganese oxide(MnO_x) with an ultra-high theoretical specific capacitance is a prospective material for supercapacitors. However, the poor conductivity degrades the capacitive performance of MnO_x. Herein, MnO_x/carbon cloth (MnO_x/CC) with a porous structure and mixed valence was in-situ prepared by an electrodeposition-electrooxidation method. The loose and porous lamellar structure of MnO_x/CC-R(V₆T₄₈₀₀)-O(V₂T₁₆₀₀) increased the contact area between the electrode and the electrolyte, provided abundant active sites and mitigated the volume expansion during the ion insertion/extraction process. Meanwhile, the optimal ratio of Mn(Ⅲ) to Mn(Ⅳ) in MnO_x/CC-R(V₆T₄₈₀₀)-O(V₂T₁₆₀₀) significantly improved the conductivity of MnO_x. Therefore, the electrochemical performance of MnO_x was effectively enhanced with a favorable specific capacitance up to 2591.2 mF∙cm⁻² (205.1 F∙g⁻¹) at 1 mA⸱cm⁻², an outstanding rate capacity (81.2% retention at 1 to 20 mA⸱cm⁻²) and superior cycle performance (91.2% after 5000 cycles). Moreover, the asymmetric supercapacitor MnO_x/CC//Fe₂O₃/CC could reach 768.2 mF⸱cm⁻² at 1 mA⸱cm⁻² and had 78.4% retention after 10000 cycles. In this work, we demonstrated the effectiveness of this in-situ electrochemical preparation of porous structure and mixed valence materials, which we hope will help develop high-performance electrode materials.