Nanoplatelets ammonium nickel-cobalt phosphate graphene foam composite as novel electrode material for hybrid supercapacitors

Highlights: • NH₄(NiCo)PO₄·H₂O pristine were successfully synthesized via hydrothermal. • Electrochemical performance of pristine has been improved by introduction of GF. • The NH₄(NiCo)PO₄·H₂O/GF was used as a positive and AC as a negative electrode. • The NH₄(NiCo)PO₄·H₂O/GF//AC demonstrate great potential for supercapacitors. -- Abstract: Nanoplatelets NH₄(NiCo)PO₄·H₂O and NH₄(NiCo)PO₄·H₂O/GF composites were synthesized through a hydrothermal approach and used as actively positive electrode for hybrid supercapacitor. Electrochemical performances of the samples were carried out in both the 3and 2-electrode measurements in 1 M KOH solution. The composite NH₄(NiCo)PO₄·H₂O/GF exhibited an improved specific capacity of 111 mAh g⁻¹ over the pristine NH₄(NiCo)PO₄·H₂O material with a 100 mAh g⁻¹, which was obtained at 0.5 Ag⁻¹. Moreover, an assembled hybrid device NH₄(NiCo)PO₄·H₂O/GF//AC revealed maximum specific energy of 47 Wh kg⁻¹ and specific power of 468 W/kg at 0.5 Ag⁻¹. The device was subjected to a long-term stability test of over 10,000 GCD cycles and could retain about 70% of its initial capacity and also proved a columbic efficiency of 99.8% at 10.0 A g⁻¹. Interestingly, the device could preserve a 1.14 V of its initial potential window of 1.4 V after being subjected to a 72 h self-discharge test, showing an efficiency of 81.4%. Based on the results discussed on this work, the NH₄(NiCo)PO₄·H₂O/GF composite could be an excellent candidate as future energy storage material, specifically supercapacitors.