Multi-level nanostructures of NiCoP/CNTs/CuO nanowire arrays/Cu foam with excellent electrochemical performance for flexible supercapacitors

Abstract

Transition metal phosphides (TMPs) have gained significant attention as promising electrode materials for supercapacitors due to their quasi-metallic properties, high electrical conductivity, and rapid redox reactions. Despite these advantages, their electrochemical performance is often hindered by low ion and electron transfer rates, as well as suboptimal cycling stability. To overcome these challenges, we have developed a novel composite electrode material by in-situ growth of Cu(OH)₂ nanowire arrays on copper foam, which acts as a robust scaffold for carbon nanotubes (CNTs) and NiCo-layered double hydroxides (NiCo-LDH). Following a phosphating process, we fabricated a core-shell structured NiCoP/CNTs/CuO nanowire array on copper foam (NiCoP/CNTs/CuO NWAs/Cu foam) with a multistage nanoarchitecture. This design features intrinsic nano-organization, low inherent resistance, short electron transport pathways, and stable electrochemical properties. In a 3 M KOH solution, the flexible NiCoP/CNTs/CuO NWAs/Cu Foam electrode achieved an impressive specific area capacitance of 15.88 F cm⁻². The assembled flexible asymmetric devices achieve an area-specific capacitance of 4718.04 mF cm⁻², an energy density of 29.79 mWh cm⁻³, and a power density of 4170.96 mW cm⁻³ at a working voltage of 1.8 V. Furthermore, after 10,000 charge-discharge cycles, the electrode retained 89.18 % of its initial capacity. This synthesis strategy for hierarchical nanostructured materials provides valuable insights for the development of next-generation materials in the field of flexible supercapacitors.