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Solid-state supercapacitors have shown extraordinary promise for flexible and wearable electronics. To date, they are still limited by relatively poor energy volumetric performances, which are largely determined by the pore structures and physicochemical properties of electrode materials. Moreover, the poor mechanical properties afforded because of the intrinsic shortcomings of electrode materials need to be resolved. Herein, we designed a flexible and solid-state yarn electrode with high porosity and high affinity toward electrolytes using poly­(3,4-ethylenedioxythiophene) (PEDOT) and Korean heritage paper (KHP). To maximize the volumetric capacitive energy storage, PEDOT-loaded conductive KHP sheets (two-dimensional) were transformed into a biscrolled yarn (one-dimensional) via simple twisting. The volumetric capacitance of the biscrolled yarn supercapacitors with 1 mm cell diameter exhibited a volumetric specific capacitance of ∼6576 mF/cm3 at a scan rate of 25 mV/s, which is attributable to the high mass loading of PEDOT as a conductive support and increased packing density. Moreover, multiple optimized yarn supercapacitors can be connected to yield a total length of 1 m, demonstrating enormous potential as a portable and wearable power supply for operating smartwatches.

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Graphene oxide (GO) is a versatile material with inherent unique properties that can be used in a wide range of applications. GO is produced from graphitic materials including graphite, and its properties can depend on the nature of stacking in the graphene structures. In this study, GO was prepared from pitch-based graphite fibers via the modified Hummer’s method and subsequently incorporated into an epoxy matrix to obtain graphene-loaded nanocomposites (EP/GO). Presented experimental results revealed that the addition of 0.6 wt% GO yielded an ∼110% increase in the fracture toughness. The corresponding fracture energies as well as the flexural strengths and flexural modulus exhibited similar trends to the fracture toughness. The thermophysical properties of the EP/GO, to further demonstrate the reinforcing effectiveness of GO, were also observed. Collectively, these results indicate that GO investigated in the study can be a viable reinforcement candidate to develop next-generation nanocomposites with multifunctional properties.

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