Breaking the performance trade-off in MoS2 supercapacitors through surface engineering with π–p coupling

Abstract

Organic ion/molecule intercalation expands interlayer spacing, thereby enhancing capacity, but it inevitably leads to structural degradation due to weakened van der Waals forces, desorption of intercalated organic ions, and the accumulation of mechanical stress during cycling with electrolyte ion intercalation, resulting in unsatisfactory cycling stability. This work presents a surface engineering strategy employing π–p coupling to overcome the critical performance trade-off between capacity and stability. Phenyltrimethylammonium (PTA⁺) cations are strongly adsorbed onto the MoS₂ surface via π–p interactions arising between the π-electron cloud of the benzene ring and the lone-pair electrons of S. The interlayer spacing is only 6.7 Å; however, both PTA⁺ and hydrated Na⁺ cannot intercalate due to spatial constraints. Thus, its energy storage mechanism mainly involves surface redox pseudocapacitance without ion intercalation, which mitigates structural deformation during cycling and thereby enables outstanding stability, with a capacitance retention of 95% after 100 000 cycles. In addition, π–p coupling enhances hydrophilicity and optimizes the electronic structure, improving specific capacitance by achieving a high specific capacitance of 293.3 F g⁻¹. This work demonstrates that π–p coupling surface engineering effectively breaks the capacity–stability trade-off, offering a promising pathway for advanced supercapacitor electrodes.