Freestanding 1T-Mn_xMo_1–xS_2–ySe_y and MoFe₂S_4–zSe_z Ultrathin Nanosheet-Structured Electrodes for Highly Efficient Flexible Solid-State Asymmetric Supercapacitors

Fabrication of hierarchical nanosheet arrays of 1T phase of transition-metal dichalcogenides is indeed a critical task, but it holds immense potential for energy storage. A single-step strategy is employed for the fabrication of stable 1T-Mn_xMo_1–xS_2–ySe_y and MoFe₂S_4–zSe_z hierarchical nanosheet arrays on carbon cloth as positive and negative electrodes, respectively. The flexible asymmetric supercapacitor constructed with these two electrodes exhibits an excellent electrochemical performance (energy density of ≈69 Wh kg⁻¹ at a power density of 0.985 kW kg⁻¹) with ultralong cyclic stability of ≈83.5% capacity retention, after 10 000 consecutive cycles. Co-doping of the metal and nonmetal boosts the charge storage ability of the transition-metal chalcogenides following enrichment in the metallic 1T phase, improvement in the surface area, and expansion in the interlayer spacing in tandem, which is the key focus of the present study. This study explicitly demonstrates the exponential enhancement of specific capacity of MoS₂ following intercalation and doping of Mn and Se, and Fe₂S₃ following doping of Mo and Se could be an ideal direction for the fabrication of novel energy-storage materials with high-energy storage ability.