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CoTe@NixSy core-shell nanowires are designed and grown on cobalt foams via hydrothermal and electrodeposition method. Structural characterizations indicate the tightly coating of NixSy nanosheets around CoTe nanowires forms the novel core-shell nanowires. Benefiting from this structural engineering design, CoTe@NixSy core-shell nanowires supported by cobalt foams deliver the high areal specific capacitance of 7.56 F cm−2 at 3 mA cm−2 and retention rate of 81.3% after experiencing 5000 cycles. It needs to be specially mentioned that CoTe@NixSy core-shell nanowires were functionally applied in aqueous/flexible hybrid supercapacitors with activated carbon as the negative materials. The aqueous hybrid devices exhibit a maximum areal energy density of 0.77 mWh cm−2 at 2.52 mW cm−2 and retention rate of 81.9% after 5000 cycles. Meanwhile, the flexible hybrid devices show superior energy-storage performance, such as high volume energy density of 3.95 mWh cm−3 at 22.64 mW cm−3, improved cycle stability (82.1% after experiencing5000 cycles), and remarkable flexibility. This work not only demonstrates CoTe@NixSy core-shell nanowires as the promising candidate of energy-storage device; but also provides a novel strategy for high-performance electroactive materials. [Display omitted] • CoTe@NixSy core-shell nanowires are constructed on foamed cobalt by the low-cost method. • CoTe@NixSy core-shell nanowires has the double synergies, fast carrier transport efficiency, etc. • Aqueous/flexible hybrid supercapacitors are built up based on core-shell CoTe@NixSy and active carbon. • Aqueous/flexible hybrid devices are promising for electric vehicles, and wearable electronics, etc. [ABSTRACT FROM AUTHOR]

Porous biomass carbon materials were successfully synthesized from wheat straw by a citric-acid-crosslinking and KOH-activating method. Structural characterization results indicate that the as-obtained biomass carbon materials have hierarchical porous structure and high specific surface area. Electrochemical test demonstrates that the porous biomass carbon materials from wheat straw have the optimal super-capacitive properties when the quality of KOH is 5 times that of the carbonization product, i.e.: high specific capacitance of 294 F g−1, superior rate performances of 200 F g−1 at 10 A g−1 and excellent cycle stabilization (97.6% of capacitance retention after 5000 cycles). More importantly, porous biomass carbon from wheat straw with the optimal performance was assembled into flexible, all-solid-state, symmetric supercapacitors. The assembled symmetric supercapacitors reveal high energy density (14 Wh kg−1 at 440 W kg−1 power density) and excellent cycle stability (only 4.3% capacitance loss after 8000 cycles). Meanwhile, the present full-cell supercapacitors manifest the remarkable flexibility, low-temperature resistance, and commercial value. Hence one can see that all-solid-state supercapacitors based on porous biomass carbon derived from wheat straw have great potential prospect in the field of portable and wearable electronic devices. Image 1 • Porous biomass carbon can be synthesized with wheat straw as the raw materials. • Biomass carbon obtained under certain condition has the optimal electrochemical properties. • Assembled flexible, all-solid-state symmetric devices have remarkable supercapacitor performance. • Porous biomass carbon derived from wheat straw has the potential applied prospect for energy storage. [ABSTRACT FROM AUTHOR]