Electroless nickel-phosphorus coated expanded graphite paper: Binder-free, ultra-thin, and low-cost electrodes for high-performance supercapacitors

Abstract In this study, electroless nickel-phosphorus(Ni-P) coating is applied on expanded graphite(EG) papers with excellent electrochemical performances and served as supercapacitor electrodes in alkaline electrolytes. The porosities of Ni-P/EG electrode, measured by mercury intrusion, are compared to expanded graphite papers. It is noticed that the as-prepared ultra-thin, binder-free, eco-friendly, and low-cost Ni-P/EG electrodes can be precisely used as an electrode for supercapacitors and show outstanding performance, including a high specific capacitance of 625 F/g at 1A/g. This material is attained an excellent energy density of 81 Wh/kg at a power density of 1005 W/kg, superior durability with 100,2% retention after 5,000 cycles. The results show that the Ni-P/EG electrode can be used as next-generation advanced metal phosphides for applications in portable electronics, supercapacitors, and wearable energy storage.