Electrochemical analysis of Co3(PO4)2·4H2O/graphene foam composite for enhanced capacity and long cycle life hybrid asymmetric capacitors

Highlights: • Co₃(PO₄)₂·4H₂O/GF composite was successfully synthesized using a hydrothermal method. • Graphene foam considerably improved the conductivity of the pristine Co₃(PO₄)₂·4H₂O. • Composite material showed pseudocapacitive electrochemical signature with high specific capacity. • Co₃(PO₄)₂·4H2O/GF was used with carbonized Fe-cation on PANI for a hybrid device. • Hybrid device showed good cycle life (99% specific capacity) retention after 10000 cycles. In this paper, we explore the successful hydrothermal approach to make Co₃(PO₄)₂·4H₂O/GF micro-flakes composite material. The unique sheet-like structure of the graphene foam (GF) significantly improved the conductivity of the pristine Co-based material, which is a key limitation in supercapacitors application. The composite electrode material exhibited superior capacitive conduct in 6 M KOH aqueous electrolyte in a 3-electrode set-up as compared to the pristine cobalt phosphate material. The material was subsequently adopted as a cathode in an asymmetric cell configuration with carbonization of Fe cations adsorbed onto polyaniline (PANI) (C-Fe/PANI), as the anode. The Co₃(PO₄)₂·4H₂O/GF//C-FP hybrid device showed outstanding long life cycling stability of approximately 99% without degradation up to 10000 cycles. A specific energy density as high as 24 W h kg⁻¹, with a corresponding power density of 468 W kg⁻¹ was achieved for the device. The results demonstrated the efficient utilization of the faradic-type Co₃(PO₄)₂·4H₂O/GF composite along with a functionalized carbonaceous electric double layer (EDL)-type material to produce a hybrid device with promising features suitable for energy storage applications.