Electrostatic self-assembly of 2D delaminated MXene (Ti3C2) onto Ni foam with superior electrochemical performance for supercapacitor

The existence of the oxygen-containing functional groups on MXene surface makes it a potential electrode material in supercapacitor based on a redox mechanism. However, the irreversible stacking of MXenes will lead to an insufficient utilization of these functional groups. To solve this problem, we fabricated a composite electrode comprised of 2D delaminated Ti₃C₂ sheets (d-Ti₃C₂) and 3D Ni foam (NF) by electrostatic self-assembly. In this electrode, d-Ti₃C₂ nanosheets are adsorbed on the surface of 3D Ni foam skeleton structure, eliminating the need for insulative polymer binders. The self-assembly strategy endows d-Ti₃C₂/NF composites with unique 2D/3D structure which possesses the merits of excellent conductivity, sufficient active sites, high charge transfer efficiency and short ions diffusion path. As a result, the d-Ti₃C₂/NF composite electrode exhibits a high specific capacitance up to 654 F g⁻¹ at 1 A g⁻¹ and good cycling stability. An asymmetrical supercapacitor with d-Ti₃C₂/NF composite as a positive electrode, bulk Ti₃C₂ (b-Ti₃C₂) as a negative electrode and 6 M KOH as electrolyte, exhibits a maximum energy density of 18.1 Wh kg⁻¹ (at 397.8 W kg⁻¹) and excellent cycling stability (80.6% after 5000 cycles). The results indicate that d-Ti₃C₂/NF composite is a promising electrode material for practical energy storage devices.