Dual-ligand modulation approach for improving supercapacitive performance of hierarchical zinc–nickel–iron phosphide nanosheet-based electrode

Abstract

Mixed nanostructured transition metal-based complex materials with hierarchical and porous architectures, built from interconnected nano-building blocks, are considered as high-performance positive electrode materials in supercapacitors (SCs). Herein, zinc–nickel–iron phosphide (ZnNiFe–P) and Zn–Ni–Fe–hydroxide precursors (ZnNiFe–OH) were combined in a 3D hierarchical and porous structure (ZnNiFe–(P/OH)) to improve their durability and electrochemical activity by incorporating a dual-ligand synergistic modulation strategy. The 3D ZnNiFe–(P/OH) architectures, comprising perfectly aligned nanosheet arrays (NSA), were successfully grown on Ni foam using a facile hydrothermal process followed by partial phosphorization. The dual-ligand ZnNiFe–(P/OH) electrode exhibited excellent specific capacitance/areal capacitance (1708Fg−1/5.64Fcm−2 for 1Ag−1), high rate performance (62% upto 15Ag−1) and good cycle life. Moreover, the ZnNiFe–(P/OH) NSA positive electrode was coupled with an activated carbon negative electrode to design an asymmetric supercapacitor device. The device delivered an excellent capacitance of ∼187Fg−1 at 0.8Ag−1, a superior energy density of ∼58.4Whkg−1 at 600Wkg−1, and an excellent power density of 11250Wkg−1 at 34.4Whkg−1 while maintaining good cycling performance (88% after 5000 cycles).