Hierarchical 3D Zn–Ni–P nanosheet arrays as an advanced electrode for high-performance all-solid-state asymmetric supercapacitors.

High-performance all-solid-state supercapacitors (SCs) have potential applications in modern electronics, such as portable and flexible electronics; however, their low specific capacity and operating voltage window limit their industrial applications. Herein, we developed a new type of zinc nickel phosphide nanosheet (Zn–Ni–P NS) arrays via a simple, scalable, and cost-effective hydrothermal and subsequent effective phosphorization technique to enhance the electrochemical performance of SCs. The hierarchical Zn–Ni–P NS array electrode exhibits an ultra-high specific capacity of ∼384 mA h g⁻¹ at a current density of 2 mA cm⁻² with excellent rate capability (79.43% of capacity retention at 50 mA cm⁻²), and outstanding cycling stability (∼96.45% of capacity retention after 10 000 cycles). Furthermore, the Zn–Ni–P NS//Fe₂O₃@NG all-solid-state asymmetric SC (ASC) delivers an ultra-high volumetric capacity of ∼1.99 mA h cm⁻³, excellent energy density of ∼90.12 W h kg⁻¹ at a power density of 611 W kg⁻¹, and extraordinary cycling stability (93.05% of initial capacity after 20 000 cycles at a high current density of 15 mA cm⁻²). Such enhanced electrochemical performances are ascribed to the 3D hierarchical nanostructures, porous nanonetworks, improved conductivity, and synergistic interaction between the active components of Zn–Ni–P NS arrays. [ABSTRACT FROM AUTHOR]