In situ growth of (NH4)2V10O25·8H2O urchin-like hierarchical arrays as superior electrodes for all-solid-state supercapacitors.

Hierarchical nanostructures with highly exposed active surfaces for use in high-performance pseudocapacitors have attracted considerable attention. Herein, we developed a one-step method for the in situ growth of (NH₄)₂V₁₀O₂₅·8H₂O urchin-like hierarchical structures on highly conductive nickel foam substrates for use as advanced electrodes for all-solid-state asymmetric supercapacitors. The in situ growth of (NH₄)₂V₁₀O₂₅·8H₂O urchin-like hierarchical structures delivers a specific capacitance of 1530 F g⁻¹ at a current density of 1.5 A g⁻¹, and retains 95.1% of the initial capacitance after 10 000 cycles, owing to the advantages of the urchin-like hierarchical structure such as more active sites for electrochemical reactions, as well as a shortened diffusion length for the charge carriers due to a binder-free effect, which exceeds that of most recently reported vanadates and polyvanadates. The as-assembled all-solid-state (NH₄)₂V₁₀O₂₅·8H₂O@Ni//PVA/KOH//RGO@Ni device exhibits a comparable capacity of 92.2 F g⁻¹ at a current density of 0.4 A g⁻¹ and excellent cycling performance through 5000 cycles. Our study provides rational guidance toward the design of novel hierarchical nanostructures of polyvanadate for solid-state supercapacitors with superior electrochemical performances in long-term cycling stability and high energy density. [ABSTRACT FROM AUTHOR]