Rapid preparation of NiCoMn hydroxide/MXene composites for electrochemical energy storage

Abstract

The novel two-dimensional layered transition metal carbides/nitrides (MXene) have the advantages of high electrical conductivity and rapid charge transport. However, when it is used as an electrode material, interlayer agglomeration and low electrochemical activity can reduce their capacitive performance. In this work, a binder-free NiCoMn hydroxide/MXene composite for supercapacitors is reported, aiming to overcome the issues of low conductivity and few active sites in MXene/transition metal compounds. The electrodes were prepared by one-step electrochemical deposition of nickel, cobalt, and manganese sulfate solutions and Ti₃C₂T_x MXene solution onto nickel foam. When the current densities are 1 A g⁻¹ and 20 A g⁻¹, the NiCoMn hydroxide/MXene composite electrode can respectively provide high specific capacitances of approximately 782.9 F g⁻¹ and 523.8 F g⁻¹, demonstrating the best performance. Additionally, the electrode exhibits satisfactory rate performance (66.9% retention from 1 A g⁻¹ to 20 A g⁻¹) and commendable cycling stability (65.8% capacitance retention after 5000 cycles at 10 A g⁻¹ constant current charge–discharge). Density functional theory indicates that the composite structures can form a synergistic effect, thereby effectively enhancing the electron transport efficiency. This study indicates that the heterostructure materials constructed by NiCoMn hydroxide and MXene is a promising electrode material for supercapacitors.