Abstract
Bimetallic sodium–nickel phosphate/graphene foam composite (NaNi4(PO4)3/GF) was successfully synthesized using a direct and simple precipitation method. The hierarchically structured composite material was observed to have demonstrated a synergistic effect between the conductive metallic cations and the graphene foam that made up the composite. The graphene served as a base-material for the growth of NaNi4(PO4)3 particles, resulting in highly conductive composite material as compared to the pristine material. The NaNi4(PO4)3/GF composite electrode measured in a 3-electrode system achieved a maximum specific capacity of 63.3 mA h g−1 at a specific current of 1 A g−1 in a wide potential range of 0.0–1.0 V using 2 M NaNO3 aqueous electrolyte. A designed and fabricated hybrid NaNi4(PO4)3/GF//AC device based on NaNi4(PO4)3/GF as positive electrode and activated carbon (AC) selected as a negative electrode could operate well in an extended cell potential of 2.0 V. As an assessment, the hybrid NaNi4(PO4)3/GF//AC device showed the highest energy and power densities of 19.5 W h kg−1 and 570 W kg−1, respectively at a specific current of 0.5 A g−1. The fabricated device could retain an 89% of its initial capacity with a coulombic efficiency of about 94% over 5000 cycling test, which suggests the material's potential for energy storage devices applications.
Highlights
With the advent of electric vehicles and portable electronic devices human demand for energy has continued to increase
We introduced a direct and easy precipitation method to synthesize a novel hierarchical nanosphere bimetallic sodium–nickel phosphate and demonstrated its capacitive capability in aqueous electrolyte
The crystal structure of the as-prepared NaNi4(PO4)[3] nanospheres was characterized by X-ray diffraction (XRD) using Diamond so ware.[31]
Summary
With the advent of electric vehicles and portable electronic devices human demand for energy has continued to increase. As a result of the intermittent nature of the green energy sources, their successful exploitation requires reliable and efficient electrical energy storage systems Following this development, the design of new energy storage devices remains an active and expanding eld of research.[4,5] Electrochemical energy storage systems, which include but are not limited to batteries and electrochemical capacitors (ECs),[6] have been embraced as efficient storage devices. The design of new energy storage devices remains an active and expanding eld of research.[4,5] Electrochemical energy storage systems, which include but are not limited to batteries and electrochemical capacitors (ECs),[6] have been embraced as efficient storage devices The reason for this is that the storage technique takes advantage of the fact that both chemical and electrical energy have a common charge carrier (known as the electron), limiting losses due to energy conversion from one form to another.
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