MXene-MnO2-CoNi layered double hydroxides//activated carbon flexible asymmetric supercapacitor

Abstract

Rational design of the structure and effective utilization of the active sites of electrode materials can improve the electrochemical performances of supercapacitors. Herein, MnO2 and CoNi layered double hydroxides (CoNi-LDHs) are sequentially deposited on carbon cloth/MXene (CC/MXene) electrode by electrodeposition to prepare CC/MXene-MnO2-CoNi-LDHs (CC/MMCoNi) electrode. The nanoarray structure can provide a large specific surface area and more channels, which facilitate rapidly ion transfer and electron migration between electrolyte and electrode. The impacts of the presence or absence of MXene and different Co and Ni ratios on the electrochemical performances are investigated in detail. It is found that the presentation of MXene on the one hand enhances the conductivity of the electrode, on the other hand supplies more active sites for the attachment of MnO2. In the situation of Co:Ni = 1:2, CoNi-LDHs having the largest nanosheets provides the high capacitance of 922 F g−1 (553 C g−1) at 1 A g−1. Asymmetric supercapacitor is successfully fabricated by assembling CC/MMCoNi positive electrode with activated carbon (AC) negative electrode. The device can provide 1.7 V voltage window and an energy density of 65 W h kg−1 at a power density of 1491 W kg−1. The device has excellent practical application ability and can effectively resist external forces, which provide theoretical basis and technical support for the subsequent development of a new generation of flexible supercapacitors.