Two-dimensional titanium carbide (MXene)-wrapped sisal-Like NiCo2S4 as positive electrode for High-performance hybrid pouch-type asymmetric supercapacitor

Rational design of electrode materials with improved electrochemical activity and stable geometrical configuration has been recognized as an effective approach for improving the electrochemical performance of supercapacitors (SCs). However, it is challenging to design novel composite materials with superior electrical conductivity and favorable specific capacitance through a facile and low cost synthesis process. Herein, NiCo2S4/MXene was successfully fabricated through electrostatic assembly by combining negatively charged delaminated titanium carbide (MXene) with positively charged sisal-like NiCo2S4, owing to the electrostatic interaction between the oppositely charged substances. The resultant NiCo2S4/MXene electrode exhibited high electrochemical performance, with a specific capacity of 1028 C g(-1) at 1A (g-)1 and 94.27% capacity retention after 5000 charge-discharge cycles. The good electrochemical performance of the NiCo2S4/MXene composite is ascribed to the synergistic coupling effect between NiCo2S4 and MXene nanosheets, which could enhance the charge transfer kinetics during the charge/discharge process. Additionally, hybrid pouch-type NiCo2S4/MXene//activated carbon (AC) asymmetric SC was assembled, which comprised NiCo2S4/MXene as positive electrode and AC as negative electrode. This device showed a stable potential window of 1.7 V, a large specific capacitance of 171.2 F g(-1) at 1A g(-1), and energy density of 68.7Wh kg(-1) at a power density of 0.85 kW kg(-1). This study provides a facile routine for developing 2D MXene-wrapped energy-storage devices with favorable electrochemical performance.