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

•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. 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.