Investigating the transformation and capacitive performance of Al-induced NiCoP nanosheets as an advanced electrode material for supercapacitors

Abstract

Challenges, such as limited active sites and undesirable cyclic stability, still hinder the practical applications of Ni-Co phosphides (NCP) based electrode materials. To solve those issues, Al-induced NCP nanosheets (NCAP) decorated on nickel foam were successfully fabricated and applied as a high-performance binder-free electrode material for alkaline supercapacitors. The transformation of NCAP during the reaction with alkaline electrolyte was also investigated. NCAP has a series of irreversible changes with the enhancement of the capacitive performance during the initial reaction with KOH to the final form of the Al-induced Ni-Co phosphides@layered double hydroxides (NCAP@LDHs) with the stable composite nanostructure. Moreover, the Density Functional Theory analysis results show that Al not only adjusts the density of states and ions migration barrier of the newly formed LDHs but also enhances the synergetic behavior between the LDHs and NCAP overall conductivity of the composites. So, a higher capacity of 1138.7 C/g was achieved in the NCAP@LDHs system compared with 643.5 C/g of NCP. The as-assembled hybrid supercapacitor (HSC) with satisfactory specific energy and specific power could light 160 LEDs and a hygrometer successfully, which suggests the potential to be applied in the energy storage field.