P-Doped NiCoS/CoZn-LDH Layered Heterostructures: Synergistically Improved Conductivity and Enhanced OH Adsorption for High-Performance Asymmetric Supercapacitors.

Doping induces lattice distortion and modifies the electronic structure of materials, thereby enhancing their electrical conductivity and chemical stability. The built-in electric field at heterojunction interfaces further promotes charge carrier migration and improves surface reaction kinetics. To leverage these synergistic effects, this study employs a combined approach involving sulfidation, phosphidation, and electrodeposition to achieve P-doping and construct a heterojunction layered structure. Specifically, P-doping is implemented through a phosphorization treatment of NiCoS grown on nickel foam, followed by the electrodeposition of CoZn-layered double hydroxide (LDH) onto the honeycomb-like NiCoS substrate. Density Functional Theory calculations demonstrate that this unique structural design markedly enhances the composite's electrical conductivity and optimizes the adsorption energy of OH ions, leading to significantly improved ion/electron reaction kinetics. The resulting P-NiCoS@CoZn-LDH electrode exhibits a high areal capacitance of 15.00 F cm at a current density of 5 mA cm. When assembled into an asymmetric supercapacitor (P-NiCoS@CoZn-LDH//activated carbon (AC)), the device achieves an energy density of 53.75 Wh kg at a power density of 205.76 W kg, while maintaining 77.36% capacitance retention after 10 000 cycles. These findings highlight the synergistic benefits of doping and heterojunction engineering in enhancing charge transport and ion adsorption capabilities, offering a promising strategy for developing high-performance supercapacitors.