Yolk-Shell Polystyrene@Microporous Organic Network: A Smart Template with Thermally Disassemblable Yolk to Engineer Hollow MoS₂/C Composites for High-Performance Supercapacitors

Yolk-shell-type polystyrene@microporous organic network (Y-PS@MON) materials were prepared by the Sonogashira coupling of tetra(4-ethynylphenyl)methane and 1,4-diiodobenzene on the surface of PS@SiO₂ and by the etching of SiO₂. The diameter of PS yolk spheres and the thickness of MON shells were 150 and ∼10 nm, respectively. The thickness of the void space between the PS yolk and the MON shell was ∼30 nm. Y-PS@MONs were used as templates for the synthesis of MoS₂/C composite materials. Because of the microporosity of the MON shells and the void space between the yolk and the shell, MoS₂ precursor compounds were efficiently incorporated into Y-PS@MONs. The heat treatment under argon resulted in the formation of hollow MoS₂/C composites. The contents of MoS₂ in the composites were systematically controlled by changing the amounts of precursor. MoS₂/C with 58 wt % of MoS₂ showed the best energy storage performance with a capacitance of 418 F/g at a 0.5 A/g current density as an electrode material of a coin cell supercapacitor, which is attributable to its hollow structure, high surface area, and the good distribution of the sliced MoS₂ in the carbon matrix. Also, the MoS₂/C-58 composite showed excellent retention of capacitances during 5000 cycles.