One-Step Synthesis of Monodispersed Mesoporous Carbon Nanospheres for High-Performance Flexible Quasi-Solid-State Micro-Supercapacitors

Cost-effective synthesis of carbon nanospheres with a desirable mesoporous network for diversified energy storage applications remains a challenge. Herein, a direct templating strategy is developed to fabricate monodispersed N-doped mesoporous carbon nanospheres (NMCSs) with an average particle size of 100 nm, a pore diameter of 4 nm, and a specific area of 1093 m² g^-1 . Hexadecyl trimethyl ammonium bromide and tetraethyl orthosilicate not only play key roles in the evolution of mesopores but also guide the assembly of phenolic resins to generate carbon nanospheres. Benefiting from the high surface area and optimum mesopore structure, NMCSs deliver a large specific capacitance up to 433 F g^-1 in 1 m H₂ SO₄ . The NMCS electrodes-based symmetric sandwich supercapacitor has an output voltage of 1.4 V in polyvinyl alcohol/H₂ SO₄ gel electrolyte and delivers an energy density of 10.9 Wh kg^-1 at a power density of 14014.5 W kg^-1 . Notably, NMCSs can be directly applied through the mask-assisted casting technique by a doctor blade to fabricate micro-supercapacitors. The micro-supercapacitors exhibit excellent mechanical flexibility, long-term stability, and reliable power output.

Phosphorus-Mediated MoS2 Nanowires as a High-Performance Electrode Material for Quasi-Solid-State Sodium-Ion Intercalation Supercapacitors

Molybdenum disulfide (MoS₂ ) is a promising electrode material for electrochemical energy storage owing to its high theoretical specific capacity and fascinating 2D layered structure. However, its sluggish kinetics for ionic diffusion and charge transfer limits its practical applications. Here, a promising strategy is reported for enhancing the Na⁺ -ion charge storage kinetics of MoS₂ for supercapacitors. In this strategy, electrical conductivity is enhanced and the diffusion barrier of Na⁺ ion is lowered by a facile phosphorus-doping treatment. Density functional theory results reveal that the lowest energy barrier of dilute Na-vacancy diffusion on P-doped MoS₂ (0.11 eV) is considerably lower than that on pure MoS₂ (0.19 eV), thereby signifying a prominent rate performance at high Na intercalation stages upon P-doping. Moreover, the Na-vacancy diffusion coefficient of the P-doped MoS₂ at room temperatures can be enhanced substantially by approximately two orders of magnitude (10^-6 -10^-4 cm² s^-1 ) compared with pure MoS₂ . Finally, the quasi-solid-state asymmetrical supercapacitor assembled with P-doped MoS₂ and MnO₂ , as the positive and negative electrode materials, respectively, exhibits an ultrahigh energy density of 67.4 W h kg^-1 at 850 W kg^-1 and excellent cycling stability with 93.4% capacitance retention after 5000 cycles at 8 A g^-1 .