Ultrathin Cu2P2O7 nanoflakes on stainless steel substrate for flexible symmetric all-solid-state supercapacitors

Abstract Phosphate based materials are emerging as advanced class of potential electrode materials for energy storage systems owing to their unprecedented redox activity, and high electrical conductivity. Fascinated by these exceptional physico-chemical properties of metal phosphates (MPhs), present work exclusively stands out as a first report on simple and industry scalable, successive ionic layer adsorption and reaction (SILAR) route to construct a binder-free electrode of ultrathin Cu2P2O7 nanoflakes with honeycomb analogues surface architecture directly grown on flexible stainless steel (SS) substrate. Unique nano-architecture with refined porosity furnishes a high specific surface area of 86.12 m2 g-1 and promotes effortless propagation of electrolyte ions, endowing enhanced extrinsic pseudocapacitive nature with excellent specific capacitance (332.9 F g-1, 399.6 mF cm-2, 268.9 F cm-3 at 10 A g-1). In addition, the contribution of surface-controlled and diffusion-limited processes to the total charge storage capacity of an electrode has been well distinguished. More importantly, the first-ever designed Cu2P2O7 based symmetric all-solid-sate supercapacitor yields competent energy density of 11.54 Wh kg-1, commendable specific power of 7.06 kW kg-1, and noteworthy retention of 85% even at 4500 charge-discharge cycles. Furthermore, supremely flexible developed device lightens up an array of 21 red light emitting diodes (LEDs) depicting its glorious commercial feasibility towards next generation portable energy storage technologies.