Rational design of Ti3C2/carbon nanotubes/MnCo2S4 electrodes for symmetric supercapacitors with high energy storage

The enhancement of electrochemical performance of supercapacitors with high-energy storage is largely determined by the selective electrode materials and their rational structural design. In this paper, we fabricated Ti3C2/CNTs/MnCo2S4 composite electrodes by electrostatic self-assembly between positively charged multiwalled carbon nanotubes (CNTs) and negatively charged Ti3C2, followed by subsequent anchoring of bimetallic sulphide MnCo2S4 nanoparticles to Ti3C2/CNTs hybrid via a two-step hydrothermal method. All the Ti3C2/CNTs/MnCo2S4 composite electrodes exhibit enhanced specific capacitance comparing with the pure Ti3C2 electrodes. The optimized Ti3C2/CNTs/MnCo2S4 electrode shows paramount gravimetric capacitance (Cs) (823 F/g at a current density of 1A/g), high rate retention (63.5% of specific capacitance retains when current density increases from 1 to 5A/g), and excellent cycling stability (94.09% after 5000 charging and discharging cycles). These improved electrochemical performances are mainly attributed to the synergistic effect of high specific capacitance from the pseudocapative material of MnCo2S4, remarkable conductivity of Ti3C2 and CNTs, and the micro-/nano-porous structures constructed by stacking Ti3C2 flakes with CNTs. Moreover, the as-synthesized Ti3C2/CNTs/MnCo2S4 electrode-based symmetric supercapacitor demonstrates a high energy density of 49.5 Wh/kg at a power density of 350 W/kg, suggesting that the electrochemical performance of Ti3C2-based supercapacitors can be substantially boosted by rational design and modification of Ti3C2 electrodes with MnCo2S4 and multilayer CNTs.