2D hierarchical nickel cobalt sulfides coupled with ultrathin titanium carbide (MXene) nanosheets for hybrid supercapacitors

Constructing multifunctional hierarchical nanocomposites is a promising strategy for enhancing the structural stability and electrochemical reaction kinetics of electrode materials. Herein, the two-dimensional (2D) hierarchical NiCoS/d-Ti₃C₂ composite is successfully synthesized through a co-precipitation and in situ sulfuration process, and shows interconnected porous network of NiCoS nanoplates on 2D d-Ti₃C₂ nanosheets. Interconnected porous network of NiCoS nanoplates can provide large surface area and rich open pores, thus leading to much redox reaction sites, while 2D d-Ti₃C₂ nanosheets with high conductivity can not only act as conductive channels for charge transfer rapidly, but also alleviate volume change of NiCoS. Benefited from the synergistic interaction between two components, the NiCoS/d-Ti₃C₂ composite electrode exhibits an enhanced specific capacity of 758.9 C g⁻¹ at a current density of 1 A g⁻¹ and good rate capability. The assembled hybrid supercapacitor (HSC) by using NiCoS/d-Ti₃C₂ composite as positive electrode and activated carbon (AC) as negative electrode delivers a high energy density of 22.6 Wh kg⁻¹ at the power density of 0.4 kW kg⁻¹ based on the total mass of active materials, and shows a good cycling stability. Our work provides a prospective and feasible strategy for the fabrication of hierarchical transition metal sulfides-based composites for high-performance supercapacitors.