Rationally designed hierarchical tree-like Fe-Co-P@Ni(OH)2 hybrid nanoarrays for high energy density asymmetric supercapacitors

Abstract

Transition metal phosphides (TMPs) are regarded as promising materials for supercapacitors (SCs) owing to their excellent redox activity and electrical conductivity. However, their inferior rate performance and poor long-term cycling stability hinder their real-world applications. Engineering nanostructured multicomponent TM-based hybrid materials with rational core@shell architectures is a promising approach to prepare advanced electrodes for SCs. Herein, hierarchical Fe-Co-P@Ni(OH)2 core@shell nanoarrays assembled from needle-type Fe-Co-P nanoarrays and ultrathin Ni(OH)2 nanosheets have been grown vertically on Ni-foam via a successive hydrothermal reaction, phosphorization, and chemical bath deposition method. The as-fabricated Fe-Co-P@Ni(OH)2 electrode exhibits an ultra-high specific capacity of 380.61 mA h g−1 at 5 mA cm−2, high rate capability (61% at 50 mA cm−2) and retains 90% of its capacity after 5000 galvanostatic charge/discharge cycles. Moreover, an asymmetric supercapacitor device was assembled by integrating Fe-Co-P@Ni(OH)2 (positive) and polyacrylonitrile-derived nitrogen doped carbon nanofiber (negative) electrodes, which delivers a high energy density of 65.09 W h kg−1 at a power density of 530.06 W kg−1, outstanding rate capability (54% at 80 mA cm−2), and excellent cycling performance.