Development of amorphous Fe‐doped nickel‐cobalt phosphate (Fe_xNiCo(PO₄)₂) nanostructure for enhanced performance of solid‐state asymmetric supercapacitors

Abstract

Summary Tremendous efforts have been made to create significant energy storage devices using nanoscale design and hybrid techniques. Toward this end, herein, we have fabricated, a binder‐free, amorphous iron‐doped nickel‐cobalt phosphate (FexNiCo(PO4)2, ie, F‐NCP) thin film on stainless steel substrate using a facile successive ionic layer adsorption and reaction (SILAR) method. Furthermore, the influence of Fe doping concentration on physico‐chemical properties is investigated. The various F‐NCP‐series electrodes contain nanoparticle‐like morphology that is beneficial for charge transfer and efficient diffusion of electrolytes in supercapacitors. Such nanoparticle‐like morphology and the synergy among iron, cobalt, and nickel elements in the F‐NCP‐3 electrode deliver a maximum specific capacity of 987 C g−1 at a current density of 2.1 A g−1 with excellent cyclic retention of 95.3% after 5000 galvanostatic charge‐discharge cycles. Especially, when an asymmetric solid‐state supercapacitor (ASSS) is fabricated in polyvinyl alcohol‐KOH gel electrolyte with reduced graphene oxide (rGO) as a negative electrode, the designed F‐NCP‐3//rGO ASSS device shows the wide (1.6 V) potential window, and a maximum specific capacitance of 116 F g−1 at 1.5 A g−1. In addition, the ASSS device gives a higher energy density of 41.26 Wh kg−1 at 1.22 kW kg−1 power density and exhibits superior cyclic stability (93% after 5000 cycles). The suggested asymmetric configuration makes a promising alternative of the cathode material to construct energy storage devices for various portable electronic systems.

Formulation of Hierarchical Nanowire-Structured CoNiO2 and MoS2/CoNiO2 Hybrid Composite Electrodes for Supercapacitor Applications

“…Conversely, in a different scenario where b is set to 0.5, the charge storage mechanism is influenced by the diffusion-controlled current (battery type). 37 Figure S6a−c displays the logarithmic relationship between current density and scan rate for CoNiO 2 , MoS 2 , and the MoS 2 /CoNiO 2 hybrid structure samples. The calculated "b" values for these samples are 0.55, 0.51, and 0.56, respectively.…”

Transition nickel/cobalt phosphates: an advanced cathode for hybrid supercapacitors

“…Reports issued on tri/multimetallic phosphates based on nickel and cobalt phosphate are tabulated in Table 4. 59,61,115,124–127…”

“…For example, Co, Ni, and Fe have similar atomic structures, which helps improve electrochemical activity and retain surface morphology. Although only one report is available on Fe-doped Ni–Co phosphate electrode material, 124 it was found that adding Fe ions resulted in multiple oxidation states and excellent conductivity. 128,129 A solid-state device was fabricated by combining Fe-doped Ni–Co phosphate as cathode and rGO as anode.…”

A Membrane‐Free Decoupled Water Electrolyzer Operating at Simulated Fluctuating Renewables with Tri‐Functional NiCo‐P Electrode

“…In recent decades, Transition metal phosphates have been widely studied as cathode materials for supercapacitors (SCs) and secondary rechargeable batteries due to their excellent electrical conductivity, active electrochemical properties, and good stability. [19][20][21][22][23][24] Besides, it is widely known that the synergistic effect of Ni and Co species plays a critical role in the remarkable electrochemical performance of NiÀ Co binary compounds. [25,26] Zhang et al synthesized nanoflowers-like NH 4 (Ni,Co)PO 4 on carbon fibers via a hydrothermal method.…”