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Lightweight structural materials are commonly used as effective fillers for advanced composites with high toughness. This study focused on enhancing the toughness of direct‐spun carbon nanotube yarns (CNTYs) by controlling the micro‐textural structure using a water‐gap‐based direct spinning. Drawing inspiration from the structural features of natural spider silk fibroin, characterized by an α‐helix in the amorphous region and β‐sheet in the crystalline region, multiscale bundles within CNTYs are reorganized into a unique nano‐coil‐like structure. This nano‐coiled structure facilitated the efficient dissipation of external mechanical loads through densification with the rearrangement of multiscale bundles, improving specific strength and strain. The resulting CNTYs exhibited exceptional mechanical properties with toughness reaching 250 J g−1, making them promising alternatives to commercially available fibers in lightweight, high‐toughness applications. These findings highlight the significance of nano‐coiling engineering for emulating bio‐inspired micro‐textural structures, achieving remarkable enhancement in the toughness of CNTYs. [ABSTRACT FROM AUTHOR]

Super strong fibers, such as carbon or aramid fibers, have long been used as effective fillers for advanced composites. In this study, the highest tensile strength of 5.5 N tex−1 for carbon nanotube yarns (CNTYs) is achieved by controlling the micro‐textural structure through a facile and eco‐friendly bundle engineering process in direct spinning without any post‐treatment. Inspired by the strengthening mechanism of the hierarchical fibrillary structure of natural cellulose fiber, this study develops multiscale bundle structures in CNTYs whereby secondary bundles, ≈200 nm in thickness, evolve from the assembly of elementary bundles, 30 nm in thickness, without any damage, which is a basic load‐bearing element in CNTY. The excellent mechanical performance of these CNTYs makes them promising substitutes for the benchmark, lightweight, and super strong commercial fibers used for energy‐saving structural materials. These findings address how the tensile strength of CNTY can be improved without additional post‐treatment in the spinning process if the development of the aforementioned secondary bundles and the corresponding orientations are properly engineered. [ABSTRACT FROM AUTHOR]

Flexible thermoelectrics that enable conformal contact with heat sources of arbitrary shape are indispensable for self‐powered wearable electronics. Scalable integration of flexible thermoelectric (TE) materials into functional devices has improved over the past few years, however, the practical applications of flexible TE materials are still hindered by low performance. Herein, highly aligned carbon‐nanotube yarns (CNTYs) are proposed, combined with selective doping via picoliter scale inkjet printing. Coagulation assisted by van der Waals forces ensures a highly aligned structure of the CNTY, thus achieving the ultrahigh power factors of 4091 and 4739 µW m−1 K−2 for the p‐ and n‐type, respectively. The proposed TE materials can be effortlessly up‐scaled into highly integrated modules via inkjet printing. A highly integrated, flexible CNTY‐based TE generator (TEG) with 600 PN pairs generates unparalleled milliwatt‐scale power at ΔT = 25 K, which is a few orders of magnitude higher than those of previously reported flexible material‐based TEGs. This TEG successfully powers a red light‐emitting diode using body heat alone, requiring no external power sources. For the seamless operation of practical applications requiring high power, this work explores the key design parameters for flexible TEGs with high performance and manufacturability and presents new platforms for self‐powered wearable electronics. [ABSTRACT FROM AUTHOR]

The realization of the exceptional intrinsic properties of carbon nanotubes (CNTs) remains a significant challenge in the field of CNT yarns and films. A fundamental lack of understanding regarding how the bundle dimensions determines the properties and how to control these bundles has resulted in insufficient performances of CNT-based components. Recognizing the absence of systematic guidelines for preparing high-performance CNT yarns or films, our focus has been on investigating the driving forces behind multidimensional CNT bundles to uncover structure-property correlations based on the dimension. We have revisited the state-of-the-art progress in engineering methods for microstructure to provide insights on achieving the desired microstructure. The interdependencies between electrical and mechanical properties, as well as the agglomeration and alignment behavior of both nanoscale and microscale bundles, emphasize the importance of selecting between dried-state engineering and swollen-state engineering of bundles within CNT yarns or films depending on their dimensions. On the basis of consideration and discussions on the advanced technologies and theoretical approaches, we have proposed possible routes to further enhance the properties of CNT yarns and films. • Systematic guidelines of fabricating high-performance CNT yarn or films are addressed. • The driving forces behind the formation and determination of CNT bundles based on dimension are highlighted. • The correlation between dimension of CNT bundles and properties of CNT yarn or film is discussed. • Tailor-fit engineering methods for CNT bundles according to dimension are reviewed. [ABSTRACT FROM AUTHOR]

Li–O 2 batteries have attracted great attention because of their high theoretical energy density, which exceeds the highest possible value of currently used Li-ion batteries. The operation of Li–O 2 batteries include the formation and decomposition of Li 2 O 2 at the cathode, and cell degradation occurs because such discharge products accumulate on the pores and cause pore clogging. For reversible charge–discharge process, in this study, a biaxially multilayered high crystalline carbon nanotube (CNT) web was designed and fabricated by a modified direct spinning method, which was the first demonstration that realize the biaxially multilayered structure in one-step process. The high crystallinity of the CNT surface reduced its decomposition and the biaxial alignment of CNT enabled the web to be opened for O 2 gas and electrolytes without pore clogging. The pore size distribution verified that effective pores were better developed in the biaxially multilayered CNT web, which facilitated the flow of O 2 gas and electrolytes. The use of this specially designed CNT as a cathode improved the cyclability by 75% and dramatically reduced the overpotential. For the practical use of Li–O 2 batteries, a 3D folded cell with biaxially multilayered CNT web electrode is fabricated and demonstrated 30 cycles at 100 W h/kg cell cutoff. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract There has been remarkable progress with regard to the fabrication of yarns based on high-performance carbon nanotubes (CNTs). However, the theoretically predicted tensile strength of CNTs has yet to be realized in practical CNT yarns or CNT-reinforced composites. Having considered that there are few systematic guidelines for preparing high-strength CNT yarns, we attempted to revisit the-state-of-the-art progress in the theories and yarn formation processes of CNT yarns and then draw possible correlations between the intrinsic and extrinsic structural parameters of elementary CNTs, yarn formation processes and the tensile strength of the resulting CNT yarns. On the basis of these considerations and discussions of advanced technologies and theoretical approaches, possible routes to improve the strength of CNT yarns further are suggested. [ABSTRACT FROM AUTHOR]

Superstrong Carbon Nanotube Yarns by Developing Multiscale Bundle Structures on the Direct Spin-Line without Post-Treatment (Adv. Sci. 2/2023) B Carbon Nanotubes b In article number 2204250, Seung Jae Yang, Chong Rae Park, and co-workers report the superstrong carbon nanotube yarns with multiscale bundle structures inspired by the strengthening mechanism of natural cellulose fibers. This unique micro-texture of yarn enables one step forward to the realization of our ultimate goal, the space elevator. [Extracted from the article]

Carbon nanotubes, high integration, inkjet-printing, thermoelectrics, wearable electronics Highly Integrated, Wearable Carbon-Nanotube-Yarn-Based Thermoelectric Generators Achieved by Selective Inkjet-Printed Chemical Doping (Adv. Keywords: carbon nanotubes; high integration; inkjet-printing; thermoelectrics; wearable electronics EN carbon nanotubes high integration inkjet-printing thermoelectrics wearable electronics 1 1 1 07/11/22 20220707 NES 220707 B Wearable Electronics b In article number 2200256, Seungjun Chung, Chong Rae Park, Heesuk Kim and co-workers fabricate a highly integrated, wearable carbon-nanotube-yarn (CNTY)-based thermoelectric generator (TEG) by precisely doping CNTY into I p i - and I n i -type segments via picoliter scale inkjet printing (depicted as splash of solution). [Extracted from the article]

Energy storage materials for energy storage system or electric vehicle should be able to supply high capacity quickly. Especially, Li-ion accessibility within graphite-based anodes is the key point to enhance mass transfer and the electrochemical performance. In terms of solvated Li-ion accessibility to the space, space in graphite-based anode is classified as two consecutive scales, channel and surface pores. A Li-ion transferrable channel is controlled by the calendering process, and surface pores are modified with a chemical vapor deposition surface coating to enhance the solvated Li-ion accessibility in each space. Cross-analysis of BET with small-angle X-ray scattering was conducted to determine whether each space is accessible and where the optimal point is. Finding correlations with the tortuosity value provided not only quantitative but also geometrical information on the space which was derived from the making process of each electrode, reflecting actual solvated Li-ion movement. This study not only suggests two distinguishable views in enhancing the accessibility of solvated Li-ions but also presents new insights to figure out how the changes in space characteristics affect the electrochemical performance. Furthermore, these findings could provide a potential strategy to estimate commercialized graphite such that the actual solvated Li-ion movement can be interpreted. [Display omitted] [ABSTRACT FROM AUTHOR]

Compact stacking of building blocks is essential in order to utilize the impermeable nature of reduced graphene oxide (rGO) for encapsulating barriers in organic electronics. To obtain the desired accumulation characteristic, rGO films were fabricated via spraying process using phase-controlled graphene oxide (GO) dispersion. The rGO laminate prepared from the isotropic-phase dispersion exhibits a more favorable face-on orientation of rGO building blocks than that from the nematic-phase GO, which implies effective stacking of building blocks. As a result, the resulting gas barrier performance of the low-temperature-annealed rGO film is superior to previously reported low-temperature solution-processed materials. Fabricated gas barriers are adopted to seal the polymer solar cell with 57.2 times longer lifetime than that of the unsealed device. A device covered by an optimized rGO/polyethylene naphthalate gas barrier maintains photovoltaic performance as high as 88% of the initial efficiency after 28 days. Image 1 [ABSTRACT FROM AUTHOR]

Intensive efforts are underway to integrate the distinct properties of individual carbon nanotubes (CNTs) into their assemblies and meet the growing demand for lightweight and strong materials. This study achieved CNT fibers (CNTFs) with high specific tensile strength (4.97 N/tex) and specific modulus (206.8 N/tex) by designing all-ring type bridges between CNTs. This reinforcement strategy involves suppressing the distortion of CNTs and promoting effective crosslinks within the fiber structure to increase the total inter-bundle interactions. The molecular-level network within the linking segment reduces vulnerability at the typically weak connection points and enhances load-transfer efficiency between crosslinked CNTs. In addition to improvements in mechanical properties, incorporating dopant groups in the bridge enhanced the electrical conductivity, reaching up to 2086 S m2/kg. This strategy provides straightforward access to multifunctional fibers beyond those of commercially accessible or literature-reported benchmark fibers. [Display omitted] • Network structure within crosslinker optimized the structural integrity of CNT fiber. • Stress dissipation within crosslinker maximized mechanical performances of CNT fiber. • Amine as n-type dopant within crosslinker enhanced electrical property of CNT fiber. [ABSTRACT FROM AUTHOR]

This study reports on a simple and efficient strategy to prepare macroscopically assembled nanostructured porous carbon (MNPC) based on metal-phenolic interactions. The abundant coordination sites contained in tannic acid enable to form a stable, interconnected hydrogel dough. The porosity evolution mechanism during carbonization process is studied by temperature programmed desorption-mass spectroscopy. Hierarchical pore structure of the MNPC can be developed by modulating the zinc chloride content. The resulting material provides versatile adsorption behaviors for various ranging from small gas molecules to larger molecules such as dye, oil and organic solvents. [ABSTRACT FROM AUTHOR]

Tremendous efforts are made to design nanostructured functional materials utilized in cathode or separator for lithium-sulfur (Li–S) batteries. However, it is still limited to grant specified functions to each component and integrate into a cell to achieve a synergistic effect for high performance. This paper presents a function-convertible synthetic platform based on metal-organic crystal derived from the liquid-solid interfacial reaction, which prepares distinct nanostructured materials with each desired function for the separator and cathode in Li–S batteries. This approach yields carbon nanorods decorated with zinc oxide quantum dots (ZQDs) on a separator, which provides both functions of alleviating the shuttle phenomenon and facilitating the conversion reactions. Further increase in temperature produces a mesostructured carbon nanorod with open porosity, supplying abundant electrochemical reaction sites for sulfur and polysulfide as a sulfur host material for the cathode. Combining specialized functions for the separator and cathode, the resulting cell exhibits outstanding rate capability and cycling performance (579.3 mAh g−1 at 5 C and 682.9 mAh g−1 at 1 C after 400 cycles). Image 1 • Metal-organic crystal is designed as function-convertible synthetic platform. • Carbon nanorods with ZnO quantum dots are coated on separator for dual functions. • Mesostructured carbon nanorods provide abundant reaction sites for sulfur. • Owing to specialized functions, the Li–S cell realizes much improved performance. [ABSTRACT FROM AUTHOR]