Layer-by-layer β-Ni(OH)2/graphene nanohybrids for ultraflexible all-solid-state thin-film supercapacitors with high electrochemical performance

With the dramatic development of portable electronics, power sources with ultrathin geometries and ultraflexibility have become an important prerequisite. In this rising field, all-solid-state thin-film supercapacitors (ASSTFSs) have received tremendous attentions due to their ultraflexibility and high safety, which are considered as competitive candidates for energy supplies in flexible electronics. However, state of the art for ASSTFSs based on carbonaceous materials and conducting polymers exhibits relatively low capacitance, which restricts their practical applications. In this study, we demonstrate the first successful application of pseudocapacitive transition metal hydroxides in all-solid-state thin-film supercapacitor (ASSTFS), exhibiting high capacitance, remarkable high-rate capability and long-term cycling stability. The free-standing thin-film electrode was fabricated by β-Ni(OH)2/graphene nanohybrids with unique layer-by-layer characteristics. The nanohybrids can be easily exfoliated into ultrathin hybrid nanoflakes with thickness of ∼10 nm and reassembled into free-standing thin-film electrode with ultraflexibility. The novel layer-by-layer structure could efficiently integrate both merits of pseudocapacitive β-Ni(OH)2 and conducting graphene, resulting in extraordinary electrochemical performance in ASSTFSs. The highest specific capacitance of 660.8 F cm−3 for ASSTFSs was achieved with negligible degradation even after 2000 charge–discharge cycles, demonstrating the high-performance electrochemical property and superior cycling stability. And the all-solid-state nature combined with superior electrochemical performance and ultraflexibility makes our device an outstanding candidate for power sources in portable electronics.

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► High-performance all-solid-state thin-film pseudocapacitors.
► Layer-by-layer β-Ni(OH)2/graphene nanohybrid.
► Device with ultraflexibility for power sources.
► High capacitance of 660.8 F cm−3 and excellent cycling stability.
► Low cost, nontoxity, environmental benign and high safety.