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A protocol has been developed for the production of epoxy-based composites containing high-volume fractions of aligned carbon nanotubes. The nanotubes were fabricated as continuous fibres or aligned mats directly from the CVD reactor, in which they were synthesized. The block composites with highly aligned and tightly packed nanotube assemblies were prepared via epoxy resin infiltration, and their volume fraction, distribution, and internal porosity being analysed prior to mechanical testing. The samples were tested in both axial tension and three-point bending. The results show that the strength and stiffness enhancements were close to pro rata with the volume fraction of the carbon nanotubes added. The failure modes were distinctly different from those characteristic of the conventional aligned carbon fibre composites. The fracture surface showed considerable evidence of pull-out of bundles of (*50) nanotubes, but the pull-out appeared to involve the resin matrix which drew out along with the bundles. Subsidiary cracks were bridged by nanotube bundles giving structures reminiscent of crazes in glassy polymers, what constitutes the distinct toughness mechanism and higher resistance to the transverse cracks propagation.

The production of continuous carbon nanotube (CNT) fibers and films has paved the way to leverage the superior properties of individual carbon nanotubes for novel macroscale applications such as electronic cables and multifunctional composites. In this manuscript, we synthesize fibers and films from CNT aerogels that are continuously grown by floating catalyst chemical vapor deposition (FCCVD) and measure thermal conductivity and natural convective heat transfer coefficient from the fiber and film. To probe the mechanisms of heat transfer, we develop a new, robust, steady-state thermal characterization technique that enables measurement of the intrinsic fiber thermal conductivity and the convective heat transfer coefficient from the fiber to the surrounding air. The thermal conductivity of the as-prepared fiber ranges from 4.7 ± 0.3 to 28.0 ± 2.4 W m(-1) K(-1) and depends on fiber volume fraction and diameter. A simple nitric acid treatment increases the thermal conductivity by as much as a factor of ∼3 for the fibers and ∼6.7 for the thin films. These acid-treated CNT materials demonstrate specific thermal conductivities significantly higher than common metals with the same absolute thermal conductivity, which means they are comparatively lightweight, thermally conductive fibers and films. Beyond thermal conductivity, the acid treatment enhances electrical conductivity by a factor of ∼2.3. Further, the measured convective heat transfer coefficients range from 25 to 200 W m(-2) K(-1) for all fibers, which is higher than expected for macroscale materials and demonstrates the impact of the nanoscale CNT features on convective heat losses from the fibers. The measured thermal and electrical performance demonstrates the promise for using these fibers and films in macroscale applications requiring effective heat dissipation.

We investigated the effects of the synthesis conditions and condensation processes on the chemical compositions and multifunctional performance of the directly spun carbon nanotube (CNT) fibers. On the basis of the optimized synthesis conditions, a two-step post-treatment technique which involved acidification and epoxy infiltration was also developed to further enhance their mechanical and electrical properties. As a result, their tensile strength and Young's modulus increased remarkably by 177% and 325%, respectively, while their electrical conductivity also reached 8235 S/cm. This work may provide a general strategy for the postprocessing optimization of the directly spun CNT fibers. The treated CNT fibers with superior properties are promising for a wide range of applications, such as structural reinforcements and lightweight electric cables.

There is increasing interest in materials that combine energy-storing functions with augmented mechanical properties, ranging from flexibility in bending to stretchability to structural properties. In the case of lithium-ion batteries, these mechanical functions could enable their integration in emerging technologies such as wearable, free-form electronics and ultimately as structural elements, for example, in transport applications. This work presents a method to produce flexible LiFePO 4 (LFP) electrodes with an extraordinary combination of electrochemical and mechanical performance. Such electrodes exhibit an exceptionally high specific toughness of 1.6 J g −1 , combined with superior rate capability (29% increase of the specific capacity at 500 mA g −1 , even with 60% reduced conductive additive content) and energy density (60% increase at 500 mA g −1 , on an LFP/Li full cell basis), with respect to reference electrodes with typical metallic current collectors. These properties are a result of the strong adhesion of the active material particles to the high surface area carbon nanotube fiber fabric, used as a lightweight, tough, and highly conducting current collector. This strong adherence minimizes electrical resistance, mitigates interfacial failure, and increases ductility through heterogeneous strain after cohesive failure of the inorganic phase. As a result, these electrodes can withstand large deformations before fracture (above 15% tensile deformation), and, even after fracture, they retain excellent electrochemical performance, with a full-electrode-normalized specific capacity of 90 mAh g −1 at 500 mA g −1 , approximately double that of unstretched, Al-supported LFP electrodes with equivalent loading.

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In the quest to increase battery performance, nanostructuring battery electrodes gives access to architectures with electrical conductivity and solid-state diffusion regimes not accessible with traditional electrodes based on aggregated spherical microparticles while often also contributing to the cyclability of otherwise unstable active materials. This work describes electrodes where the active material and current collector are formed as a single nanostructured composite network, consisting of macroscopic fabrics of carbon nanotube fibers covered with conformal MoS 2 grown preferentially aligned over the graphitic layers, without a metallic current collector or any conductive or polymeric additives. The composite fabrics of CNTF/MoS 2 retain high toughness and show out-of-plane electrical conductivity as high as 1.2 S/m, above the threshold to avoid electrical transport-limited performance of electrodes (1 S/m) and above that of control nanocomposite lithium-ion battery electrodes (0.1 S/m) produced from dispersed nanocarbons. Cycled against Li, they show specific capacity as high as 0.7 A h/g along with an appreciable rate capability and cycling stability in low (108% capacity retention after 50 cycles at 0.1 A/g) as well as high current density (89% capacity retention after 250 cycles at 1 A/g). The composite fabrics are flexible, with high tensile toughness up to 0.7 J/g, over two orders of magnitude higher than conventional electrodes or regular MoS 2 materials, and full-electrode capacity above state-of-the-art at different current densities.