CNT Network Research Articles

Transparent and flexible high-power supercapacitors based on carbon nanotube fibre aerogels.

In this work, we report the fabrication of continuous transparent and flexible supercapacitors by depositing a CNT network onto a polymer electrolyte membrane directly from an aerogel of ultra-long CNTs produced floating in the gas phase. The supercapacitors show a combination of a power density of 1370 kW kg-1 at high transmittance (ca. 70%), and high electrochemical stability during extended cycling (>94% capacitance retention over 20 000 cycles) and against repeated 180° flexural deformation. They represent a significant enhancement of 1-3 orders of magnitude compared to prior state-of-the-art transparent supercapacitors based on graphene, CNTs, and rGO. These features mainly arise from the exceptionally long length of CNTs, which makes the material behave as a bulk conductor instead of an aspect ratio-limited percolating network, even for electrodes with >90% transparency. The electrical and capacitive figures-of-merit for the transparent conductor are FoMe = 2.7, and FoMc = 0.46 F S-1 cm-2 respectively.

Constructing 2D SnS@C nanosheets anchored on interconnected carbon nanotube networks as advanced anode materials for lithium ion and sodium ion batteries

The huge volume change and sulfur dissolution during the repeated discharge/charge process is believed to be the main cause of fast capacity decay and poor rate capability of SnS for LIBs and SIBs. Here, SnS@C nanosheets anchored on interconnected CNT networks are designed and prepared as anode materials for LIBs and SIBs is reported. Thanks to the synergistic function between SnS nanosheets, CNT and carbon coating layers, the obtained SnS/CNT@C composite exhibits outstanding cycling/rate performance for LIBs and SIBs. Meanwhile, high specific capacity of 494.9 mAh g−1 is maintained after 400 loops at 1.0 A g−1, excellent rate performance (431 mAh g−1 at 5.0 A g−1) is achieved for LIBs. Furthermore, SnS/CNT@C composite also demonstrated a high reversible capacity (582.6 mAh g−1 at 0.2 A g−1) and long-term cycling performance (243.3 mAh g−1 is obtained after 400 loops at 0.5 A g−1) for SIBs.

Constructing the core–shell structured island domain in polymer blends to achieve high dielectric constant and low loss

AbstractCarbon nanotubes (CNTs) and barium titanate (BaTiO3) (BT) were simultaneously introduced into the immiscible blend poly(ethylene‐co‐vinyl acetate)/thermoplastic urethane (EVA/TPU), and the EVA/TPU/CNT/BT quaternary polymer composite blends with core–shell structured island TPU domain were successfully prepared, in which CNTs in the TPU domain act as the core and the BT spheres at the interface of the TPU and EVA act as the shell. A core–shell structured island can lead to the formation of micro‐capacitors and further accumulate electron storage owing to the incorporation of CNTs and BT; on the other hand, a BT shell can be assembled along the TPU spheres, reducing the possibility of formation of a conductive CNT network, resulting in suppressed dielectric loss. Therefore, CNTs and BT were tailor‐made into blend composites with a core–shell structured domain, which can achieve an increased dielectric constant by 176% and decreased low dielectric loss by 80% compared with the blend composites with only CNTs in the TPU domain. © 2019 Society of Chemical Industry

Three-dimensionally interconnected Co9S8/MWCNTs composite cathode host for lithium–sulfur batteries

Abstract Several challenging issues, such as the poor conductivity of sulfur, shuttle effects, large volume change of cathode, and the dendritic lithium in anode, have led to the low utilization of sulfur and hampered the commercialization of lithium–sulfur batteries. In this study, a novel three-dimensionally interconnected network structure comprising Co9S8 and multiwalled carbon nanotubes (MWCNTs) was synthesized by a solvothermal route and used as the sulfur host. The assembled batteries delivered a specific capacity of 1154 mA h g−1 at 0.1 C, and the retention was 64% after 400 cycles at 0.5 C. The polar and catalytic Co9S8 nanoparticles have a strong adsorbent effect for polysulfide, which can effectively reduce the shuttling effect. Meanwhile, the three-dimensionally interconnected CNT networks improve the overall conductivity and increase the contact with the electrolyte, thus enhancing the transport of electrons and Li ions. Polysulfide adsorption is greatly increased with the synergistic effect of polar Co9S8 and MWCNTs in the three-dimensionally interconnected composites, which contributes to their promising performance for the lithium–sulfur batteries.

Modeling of CNT-reinforced nanocomposite with complex morphologies using modified embedded finite element technique

In this article, we overcome the limitations of traditional finite element (FE) method in modeling CNT-reinforced nanocomposites with complex morphologies by developing a modified embedded finite element (mEFE) method. The composite constituents in the mEFE model are discretized independently but simulated simultaneously as a coupled system. The major advantage of this approach is discretizing the matrix as a regular grid, irrespective of the complex nature of the CNT network. The developed modeling approach allowed us to simulate realistic representative volume elements (RVEs) containing randomly dispersed CNTs of different curvatures, orientations, aspect ratios and volume fractions. An advanced Monte Carlo based algorithm was also developed to generate complex CNT networks. The proposed mEFE method requires a significantly shorter preprocessing effort and is more computationally efficient when compared to traditional FE method. It allowed us to study large scale RVEs reinforced with high CNT concentrations. The results of this idealised case showed that the elastic modulus of the nanocomposite increases with increasing the volume fraction of the CNTs; reaching 200 % improvement at 5 % volume fraction. However, the enhancement in the properties was not obvious at higher concentrations due to the poor dispersion and agglomeration of the dispersed CNTs.

Electro and Light-Active Actuators Based on Reversible Shape-Memory Polymer Composites with Segregated Conductive Networks

Reversible shape-memory polymers (RSMPs) show great potential in actuating applications because of its repeatability among many other advantages. Indeed, in many cases, multiresponsive RSMPs are more expected, and the strategy to introduce functional fillers without deteriorating the reversible deformation performance is of great importance. Here, a facile strategy to balance the electro, photothermal performance, and molecular chain mobility is reported. Segregated conductive networks of carbon nanotubes (S-CNTs) are constructed in the poly(ethylene-co-octene) (POE) matrix at a relatively low filler loading, which renders the composite good electrical, photothermal, and actuating properties. A low percolation threshold of 0.25 vol % is achieved. The electrical conductivity is up to 0.046 S·cm-1 for the POE/S-CNT composites with 2 vol % CNT, and the absorption of light (760 nm) is above 90%. These characteristics guarantee that the actuator can be driven at low voltage (≤36 V) and suitable light intensity (250 mW·cm-2) with a good actuating performance. An electric gripper and a light-active crawling robot demonstrate the potential applications in multiresponsive robots. This work introduces a facile strategy to fabricate multiresponsive RSMPs by designing CNT network structures in polymer composites and holds great potential to enlarge the applications of RSMPs in many areas including artificial muscles and bionic robots.

Spray-Drying As a Versatile Synthesis Method for Fluorophosphate-Based Compounds As Cathodes Material for Na-Ion Batteries

Fluorophosphate compounds attract much attention as cathode materials for Na-ion batteries. Indeed, thanks to the inductive effect of the fluoride and phosphate groups, such compounds exhibit a relatively high working potential and good theoretical capacity [1]. In this work, we focus on the iron (Na2FePO4F (NFPF)) and vanadium (Na3V2(PO4)3F3(NVPF)) based fluorophosphate materials which are characterized by a high theoretical capacity of 124 mAh/g and 128 mAh/g, respectively. In addition, the iron-based phase is also more environmental friendly due to the low toxicity of the iron. The preparation of such complex phases using conventional solid-state route requires at least two steps with long heat treatment durations. Here, we report a facile aqueous synthesis using the spray-drying method that can be used for both NFPF and NVPF materials and that can be tuned in order to optimize the composition and the morphology of the desired materials. The major limitation of phosphate-based electrodes is their low intrinsic electronic conductivity. The synthesis of composites with carbon is an effective strategy for the enhancement of the electronic conductivity of these compounds. Spray-drying is a suitable method to incorporate carbon in composite compounds due to the high homogeneity of the obtained particle [2]. It is also a cost effective and up-scalable technique which can produce large quantities of the desired material. Here, we report the influence of the carbon addition of the structural, morphological and electrochemical properties of NFPF and NVPF compounds. The prepared composite materials were investigated by combining several characterisation techniques such as XRD, SEM and TEM. The electrochemical properties were evaluated by galvanostatic cycling and electrochemical impedance spectroscopy in Na-ion batteries. [1] Eshraghi, N., Caes, S., Mahmoud, A., Cloots, R., Vertruyen, B., & Boschini, F. (2017). Sodium vanadium (III) fluorophosphate/carbon nanotubes composite (NVPF/CNT) prepared by spray-drying: good electrochemical performance thanks to well-dispersed CNT network within NVPF particles. Electrochimica Acta, 228, 319-324. [2]Vertruyen, B., Eshraghi, N., Piffet, C., Bodart, J., Mahmoud, A., & Boschini, F. (2018). Spray-Drying of Electrode Materials for Lithium-and Sodium-Ion Batteries. Materials, 11(7), 1076.

Heterogeneous CoFe–Co8FeS8 nanoparticles embedded in CNT networks as highly efficient and stable electrocatalysts for oxygen evolution reaction

It is essential to explore high-efficiency and low-cost electrocatalysts to replace noble metal based electrocatalysts for promoting the efficiency of water splitting and obtaining clean hydrogen energy. Herein, for the first time, self-assembled heterogeneous CoFe–Co8FeS8 nanoparticles embedded in CNT networks (CoFe/Co8FeS8/CNT) are synthesized via a facile microwave-assisted sulfidation and annealing process. Compared to CoFe/CNT or Co8FeS8/CNT, the CoFe/Co8FeS8/CNT delivers much better performance for oxygen evolution reaction (OER): it shows an Ultralow Tafel slope of 38 mV dec−1; it affords a large current density of 10 mA cm−2 only requiring a small overpotential of 290 mV; in addition, it demonstrates good long-term stability. The outstanding OER performance of CoFe/Co8FeS8/CNT is attributed to its unique porous nanoarchitecture constructed by heterogeneous CoFe–Co8FeS8 nanoparticles homogenously embedded in highly conductive CNT networks, which can not only enable full utilization of electrocatalytic active sites and provide conductive pathways for efficient charge transfer between nanoparticles and CNT, but also accelerate gas bubbles evolving and releasing. This work provides insight into microwave-assisted synthesis of highly efficient non-precious transition metal sulfide-based electrocatalysts with rationally designed nanoarchitecture for OER.

Exploiting the piezoresistivity and EMI shielding of polyetherimide/carbon nanotube foams by tailoring their porous morphology and segregated CNT networks

Microporous polyetherimide/carbon nanotube (PEI/CNT) foams with high strength and segregated structure have been developed by sinter molding and supercritical CO2 (scCO2) foaming. The segregated composite foams exhibited an excellent conductivity and EMI shielding effectiveness of 7.98 S/m and 32.3 dB, respectively., along with the low percolation threshold of 0.06 vol%. Benefiting from the unique segregated microcellular structure, the composite foams exhibited superb reversibility and reproducibility in terms of electrical resistance during the multiple cyclic compression-releases. For instance, 80.3% change in resistance variation ratio was obtained under the external applied pressures (0–18.36 MPa) and compression strains (0–10%), due to the “compression-recovery” transition of the segregated porous structure and conductive skeleton. Besides, the electrical and piezoresistive properties of the segregated PEI/CNT foams are strongly associated with their density. Our current effort sets a flexible path to integrate EMI shielding with piezoresistivity properties that could be used in many advanced applications.

Suspended 3D AgNPs/CNT nanohybrids for the SERS application

There dimensional (3D) metallic nanohybrids have attracted attentions for the applications in nanophotonic devices, catalysis and biosensor. Here, the 3D suspended Ag nanoparticles/Carbon nanotubes (AgNPs/CNTs) nanohybrids, obtained by self-aggregating AgNPs onto the suspended CNT networks, are synthesized and used for the SERS application. The electric field distribution with the near-field and far-field coupling can be obtained by the optimization of the nanogaps of the AgNPs. Such suspended AgNPs/CNTs nanohybrids are studied to be used as the ultra-sensitive SERS biosensor, benefiting from the bio-compatibility and chemical absorption of the CNT networks and the EM enhancement of the 3D denser “hotspots”. R6G molecules with a concentration as low as 10−15 M can be clearly detected, demonstrating their excellent Raman enhancement.

Three-Dimensional Self-Standing and Conductive MnCO3@Graphene/CNT Networks for Flexible Asymmetric Supercapacitors

The practical applications of flexible supercapacitor depend strongly on the successful fabrication of advanced electrode materials with high electrochemical performance. Herein, three-dimensional ...

Scalable Synthesis of Heterogeneous W–W2C Nanoparticle-Embedded CNT Networks for Boosted Hydrogen Evolution Reaction in Both Acidic and Alkaline Media

Practical hydrogen production via the hydrogen evolution reaction (HER) is reported as a clean and sustainable strategy for future energy demands. Tungsten (W)-based compounds are reported as promi...

Selenium Nanocomposite Cathode with Long Cycle Life for Rechargeable Lithium‐Selenium Batteries

AbstractSelenium (Se) is a potential cathode material for high energy density rechargeable lithium batteries. In this study, a binder‐free Se‐carbon nanotube (CNT) composite electrode has been prepared by a facile chemical method. At initial state, Se is present in the form of branched nanowires with a diameter of <150 nm and a length of 1–2 μm, interwoven with CNTs. After discharge and re‐charge, the Se nanowires are converted to nanoparticles embedded in the CNT network. This synthesis method provides a path for fabricating the Se cathodes with controllable mass loading and thickness. By studying the composite electrodes with different Se loading and thickness, we found that the electrode thickness has a critical impact on the distribution of Se during repeated cycling. Promising cycling performance was achieved in thin electrodes with high Se loading. The composite electrode with 23 μm thickness and 60 % Se loading shows a high initial capacity of 537 mAh g−1 and stable cycling performance with a capacity of 401 mAh g−1 after 500 cycles at 1 C rate. This study reports a synthesis strategy to obtain Se/CNT composite cathode with long cycle life for rechargeable Li−Se batteries.

Highly conductive ultra-sensitive SWCNT-coated glass fiber reinforcements for laminate composites structural health monitoring

In the present study, hierarchical single-wall carbon nanotube covered Glass fibres (GF-CNT) are developed for self-sensing Structural Health Monitoring (SHM) of epoxy laminate composites. The unidirectional (UD) CNT-modified glass fibers were fabricated by a versatile and scalable wet-chemical blade coating deposition process under ambient conditions. GF-CNT were employed to manufacture UD damage sensing composite laminates. Scanning Electron microscopy (SEM) revealed an extremely homogeneous CNT nanolayer consisting of highly entangled CNT networks covering fully the GF surfaces. A comprehensive electrical characterization of the manufactured laminate was carried out, revealing a strongly orthotropic response in terms of electrical resistivity. The damage sensing capability of the new developed “smart” reinforcement material was verified taking advantage of mode I Double Cantilever Beam (DCB) tests carried out on specimens with a pre-delamination. The electrical resistance, measured during the tests, exhibited a pronounced increase proportional to the delamination growth. The experimental data were also compared with the assessment of a predictive analytical model, showing a very satisfactory agreement.

Three-dimensional carbon-coating silicon nanoparticles welded on carbon nanotubes composites for high-stability lithium-ion battery anodes

Although silicon (Si) is regarded as one of promising anode materials in next-generation lithium-ion batteries (LIBs) due to the high specific capacity, commercial application is stifled by the large volume effect and small electric conductivity. Using rice husk (RH) biomass as nano Si source (RH-Nano Si), here we designed and fabricated the three-dimensional (3D) carbon-hybridized nano-Si hierarchical architecture composite (RH-Nano Si@C/CNT) via assembling Si with CNT by the self-electrostatic route, reinforcing by hydrothermal treating in a glucose solution, and calcination in Ar. In RH-Nano Si@C/CNT, the Si nanoparticles are anchored on the 3D conductive CNT network by the glucose-derived carbon through welding and coating, thus providing enhanced electrical contact and high structural integrity. As anode materials, RH-Nano Si@C/CNT exhibits improved rate capability and prolonged cycling stability compared to Si and CNT self-electrostatic sample. Boasting a high reversible capacity of 989.5 mAh g−1 at 0.5C (1C = 4.2 A g−1) and 345 mAh g−1 at 3C as well as low capacity decay of 0.035% per cycles after 1000 cycles, RH-Nano Si@C/CNT produced by this technique is promising as anodes in LIBs.

Porous polyaniline/carbon nanotube composite electrode for supercapacitors with outstanding rate capability and cyclic stability

Polyaniline (PANI) is one of the most widely used organic electrode materials for supercapacitors. It has advantages such as good environmental stability and low cost, whereas it is difficult to achieve high capacitance, good rate capability and long cycle life simultaneously. In this work, a series of porous polyaniline/carbon nanotube (PANI/CNT) composite materials are prepared by chemically grafting PANI on CNTs and creating interpenetrating pores via templating using CaCO3 nanoparticles, and then studied as electrode materials for supercapacitors. As PANI is covalently grafted on CNT networks formed in the electrode, the delocalization of electrons improves electron transport in the electrode and the stability of PANI in redox cycling process. The porous morphology created provides sufficient channels for the transport of ions. As a result, the optimized PANI/CNT composite exhibits a high capacitance of 1266 F g−1 at a specific current of 1 A g−1, and even at a specific current of 128 A g−1 the specific capacitance could reach 864 F g−1. Moreover, after cycling tests of 10,000 cycles, it remains 83% of its capacitance at the first cycle. The excellent rate performance and cycle stability of the porous PANI/CNT composite makes it a promising high-performance electrode material for supercapacitors.

Tensile strength prediction of carbon nanotube reinforced composites by expansion of cross-orthogonal skeleton structure

Kolarik suggested a cross-orthogonal skeleton model (COS) for tensile strength of polymer blends with co-continuous morphology assuming interfacial parameter and percolating effect. In the current study, this model is developed for polymer/carbon nanotubes (CNT) nanocomposites (PCNT) containing CNT network above percolation threshold. Kolarik model is joined with Pukanszky equation for tensile strength of polymer nanocomposites to express “A” interfacial parameter by CNT dimensions, interphase properties and the density and strength of network. The experimental data and the justification of trends between strength and all parameters show the predictability of the suggested model. The strength meaningfully changes at different dimensions of CNT and network density (N). A main improvement in the strength of PCNT (250%) is obtained by aspect ratio (length per diameter) of 1000 and network density of 2000.

W2C nanodot-decorated CNT networks as a highly efficient and stable electrocatalyst for hydrogen evolution in acidic and alkaline media.

Although tungsten carbide (W2C) has long been reported as an excellent platinum-like catalyst, it is still a challenge to synthesize W2C as an electrocatalyst for a highly efficient hydrogen evolution reaction (HER) due to its high onset overpotential, inevitable aggregation, and lack of a scalable and controllable synthesis method. Herein, we synthesized W2C nanodot-decorated CNT networks (W2C@CNT-S) via a facile and scalable spray drying method followed by a carbonization process. It is demonstrated that this unique nanoarchitecture, constructed by ultrafine W2C nanodots homogeneously decorated on a three-dimensional and conductive CNT skeleton, leads to the exposure of abundant catalytic sites and promotes highly efficient electron transfer and ion diffusion during the HER process. As a result, in acidic and alkaline media, the optimized W2C@CNT-S hybrid exhibited excellent HER performance with very low onset overpotentials of only 60 and 40 mV (vs. RHE) and very small Tafel slopes of 57.4 and 56.2 mV dec-1, and only needed 176 and 148 mV (vs. RHE) to obtain a current density of 10 mA cm-2, respectively; it also showed outstanding long-term durability even after a 30-hour test in both acidic and alkaline media. This study presents an overview of a low-cost and scalable spray-drying strategy to synthesize a high-performance carbide-based electrocatalyst for hydrogen evolution.

Enhancing the EMI shielding of natural rubber-based supercritical CO2 foams by exploiting their porous morphology and CNT segregated networks.

Natural rubber/carbon nanotubes composite foams (F-NR/CNTs) with high electrical conductivity and excellent electromagnetic interference (EMI) performance were developed through a multi-step process including: (a) CNTs assembled on natural rubber latex particles, (b) pre-crosslinking of natural rubber, (c) supercritical carbon dioxide foaming of pre-crosslinked composite samples and (d) post-crosslinking of foamed composite samples. A closed-cell porous structure and a segregated CNT network are clearly observed in the resulting foams. Due to this morphology, F-NR/CNTs exhibit low density, good mechanical properties, and high electrical conductivity. Owing to the multiple radiation reflections and scattering between the cell-matrix interfaces, the composite foams presented an excellent specific shielding effectiveness (SSE) of 312.69 dB cm2 g-1 for F-NR/CNTs containing 6.4 wt% of CNTs, which is significantly higher than those already published for rubber composites containing comparable filler content. Furthermore, the analysis of EMI SE highlights that absorption efficiency is more significant than reflection efficiency, implying that most of the incident electromagnetic radiation is dissipated in the form of heat. This work provides the fundamentals for the design of innovative light weight and efficient EMI shielding foams characterized by a three-dimensional segregated CNT network with huge potential for use in the electronics and aerospace industries.

The Influence of CNT Network Functionalization in Gaseous Media CL2, NO2, O3 on Their Electrical Properties

The Influence of CNT Network Functionalization in Gaseous Media CL2, NO2, O3 on Their Electrical Properties