Chemically grown Co2P2O7 microplates: extrinsic pseudocapacitance enriched ultraflexible all-solid-state supercapacitors

Abstract

This study explores a cost-effective, scalable and simple one-pot solution route, namely, the chemical bath deposition method, to grow a platelet-like morphology of cobalt pyrophosphate (Co₂P₂O₇) in thin film form through a binder-free approach. The layered structure of pyrophosphates, rich redox chemistry of cobalt, and evolved anisotropic plate-like microstructure with an immense specific surface area of 52.1 m² g⁻¹ and extreme porosity, synergistically stimulates the extrinsic-type of charge storage behaviour, resulting in high storage capacity with well-rated performance. Interestingly, the flexible all-solid-state symmetric supercapacitor device (FSSD) constructed by sandwiching symmetric Co₂P₂O₇ electrodes with the aid of a freestanding PVA–KOH membrane presents a remarkable energy density of 33.8 W h kg⁻¹ at a power density of 602.7 W kg⁻¹ along with a robust 8000-cycle life with 88% capacitive retention. The well-intact and interwoven device unveiled exhilarating mechanical bendability with a capacity retention of 140%. The first-ever designed, supremely flexible Co₂P₂O₇ supercapacitor device demonstrated the lighting of 21 red light-emitting diodes (LEDs) when connected in series, indicating its energy storage prospects for intelligent miniaturized electronic circuits.