Yarn supercapacitors have great potential in future portable and wearable electronics because of their tiny volume, flexibility and weavability. However, low-energy density limits their development in the area of wearable high-energy density devices. How to enhance their energy densities while retaining their high-power densities is a critical challenge for yarn supercapacitor development. Here we propose a coaxial wet-spinning assembly approach to continuously spin polyelectrolyte-wrapped graphene/carbon nanotube core-sheath fibres, which are used directly as safe electrodes to assembly two-ply yarn supercapacitors. The yarn supercapacitors using liquid and solid electrolytes show ultra-high capacitances of 269 and 177 mF cm−2 and energy densities of 5.91 and 3.84 μWh cm−2, respectively. A cloth supercapacitor superior to commercial capacitor is further interwoven from two individual 40-cm-long coaxial fibres. The combination of scalable coaxial wet-spinning technology and excellent performance of yarn supercapacitors paves the way to wearable and safe electronics.

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Macroscopic assembled, self-standing graphene and graphene oxide (GO) films have been demonstrated as promising materials in many emerging fields, such as Li ion battery electrodes, supercapacitors, heat spreaders, gas separation, and water desalination. Such films were mainly available on centimeter-scale via the time-and energyconsuming vacuum-filtration method, which seriously impedes their progress and large-scale applications. Due to the incompatibility between large-scale and ordered assembly structures, it remains a big challenge to access large-area assembled graphene thick films. Here, we report for the first time a fast wet-spinning assembly strategy to produce continuous GO and graphene thick films. A 20 m long, 5 cm wide, well-defined GO film was readily achieved at a speed of 1 m min −1 . The continuous, strong GO films were easily woven into bamboo-mat-like fabrics and scrolled into highly flexible continuous fibers. The reduced graphene films with high thermal and moderate electrical conductivities were directly used as fast-response deicing electrothermal mats. The fast yet controllable wet-spinning assembly approach paves the way for industrial-scale utilization of graphene.

Fiber-based asymmetric micro-supercapacitor (F-asym-mSC) is assembled by core–sheath graphene fiber decorated by MnO2as the positive electrode and graphene-carbon nanotubes hybrid fiber as the negative electrode. The F-asym-mSC shows the highest energy density (11.9 μWh cm−2) for fiber-based supercapacitors and paves the way to high energy density, wearable, and flexible electronic devices.

We report a facile strategy to synthesize silica nanoparticles-coated graphene oxide (GO-SiO2) nanohybrids in a water-alcohol mixture at room temperature. AFM observations revealed that silica nanoparticles with ca. 50 nm in size were densely and evenly covered on graphene oxide sheets. Due to the space layer of silica nanoparticles, micro-scale GO-SiO2 hybrid plates could be individually dispersed in water and polar organic solvents, promising good solution-based processibility. The growth process of GO-supported silica is traced by TGA and XRD measurements, showing that 24 hours is enough to achieve a fine cover effect for the disappearance of (002) diffraction peak of GO. Based on the high dense overlaying of silica nanoparticles, up to micro-scale silica sheets with thickness of ca. 8 nm were readily fabricated by burning GO-SiO2 at 650 °C in air. Likewise, a centimeter-scale semitransparent film of silica nanosheets was prepared by calcining a GO-SiO2 film. Interestingly, the GO-SiO2 nanohybrids exhibit excellent hydrophilic nature and can be directly applied as a general kind of building blocks to construct large-area superhydrophilic surfaces on arbitrary substrates (e.g., lotus leaf, ceramic tile and polypropylene) through the simple drop-coating method. Such a coating methodology paves the way for making large-area superhydrophilic surface without extra process treatments and damaging the intrinsic structure of substrates.