Three-dimensional Conductive Network Research Articles

Flexible and stretchable polyester@reduced graphene oxide composite fabric for tunable electromagnetic absorption

The widespread application of 5 G wireless communication and flexible electronic devices has put forward new demands for electromagnetic (EM) absorbing materials. In this work, a flexible composite fabric was successfully prepared by using polyester (PET) knitted fabric as an elastic scaffold and subsequently anchoring reduced graphene oxide (rGO) through a simple impregnation-drying coating method. Regulating the concentration of graphene oxide (GO) impregnation solution can effectively control the rGO loading content for adjusting the EM parameters of PET@rGO composite fabric. When the concentration is 2.0 mg/mL, the as-prepared PET@rGO exhibits the optimum reflection loss (RL) value of −24.53 dB at 12.4 GHz and a corresponding effective absorption bandwidth (EAB, RL≤−10 dB) of 3.20 GHz (9.20–12.40 GHz). The impressive absorption property attributed to the synergistic effect of impedance matching and dielectric loss originated from the three-dimensional (3D) conductive network on fabric interlaced structures. More importantly, stretching PET@rGO composite fabrics to different deformations can dynamically adjust the EM absorption properties while maintaining the knitted structure. This work demonstrates an efficient avenue for the rational design of next-generation EM absorbing fabric, showing latent applications in flexible functional electronics.

Flexible construction of three-dimensional continuous conductive structure by hollow carbon sphere and CNT for promoted ions transport in flow-electrode capacitive deionization

Flow-electrode capacitive deionization (FCDI) emerges as a promising desalination technique, characterized by its unlimited desalination capacity, seamless operation, and easy scalability. However, challenges such as discontinuous electronic network, inadequate dispersion of suspended carbon particles, and hindered electron/ion transport pathways have impeded the full potential of FCDI. This study addresses the above issues by synergistically leveraging the advantage of hollow carbon sphere (HCS) and CNT to construct a flexible, continuous three-dimensional conductive network (HCS@CNT) as the flow-electrode for FCDI. The incorporation of HCS substantially improves the fluidity and effective collision of the flow-electrode slurry. Simultaneously, the bridging effect of CNT facilitates smooth ion transport routes and rapid electron/ion transfer. Moreover, the spherical structure of HCS as a node can effectively alleviate the agglomeration of CNT due to its inherent good fluidity. As a result, the meticulously designed HCS@CNT flow-electrode demonstrates outstanding rheological behavior with excellent hydrophilicity, a large specific capacitance, and low ion diffusion resistance. During desalination tests, the HCS@CNT flow-electrode exhibited a high average salt removal rate (0.56 µmol min−1 cm−2), appropriate energy-normalized removal salt (15 µmol J−1), and notable charge efficiency (89 %) in a 1 g L-1 NaCl solution. Impressively, it maintained good stability and continuity over a continuous 10-hour desalination process, showcasing substantial potential for treating highly concentrated saline water. In addition, density functional theory (DFT) calculations provided additional insights, confirming that the construction of HCS@CNT facilitated interfacial charge transfer and electron transport from HCS to CNT. This innovative approach sheds light on enhancing electron/ion transfer by harnessing the unique structural characteristics of the flow-electrode.

A novel linear temperature thermistor in the xAl2O3-(1-x)CdSnO3 system

Negative Temperature Coefficient (NTC) thermistors, known for their high sensitivity and fast response, find wide applications in national economy, military, aerospace and various other fields. The study of NTC thermistors with linear temperature-resistance is of great significance in streamlining circuit designs and developing high-performance electronic ceramics. This study focuses on the synthesis of a linear thermistor material in xAl2O3-(1-x)CdSnO3 system by a solid-phase reaction method. Through the introduction of th high-resistance Al2O3 phase, a three-dimensional conductive network is established with Al2O3 and CdSnO3, resulting in the acquisition of linear electrical properties. These properties have exhibited excellent linear NTC variation within the temperature range of 308 K–458 K. Notably, at x = 0.2, the thermistor shows the highest linearity (R2 = 0.9984). Additionally, the complex impedance spectral analysis has helped build resistive and capacitive conductivity models revealing the linearization mechanisms.

Carbon Nanofibers-Based Anodes for Potassium-Ion Battery.

In recent years, with the global warming getting worse and increasing demand for energy, countries around the world are trying to develop new energy storage technologies to solve this problem. Currently, potassium-ion batteries (PIBs) have attracted tremendous attention from researchers as low-cost and high-performance energy storage devices. However, due to the huge ionic radius of K+, PIBs face significant volume expansion during cycling, which can easily lead to the collapse of electrode structures. In addition, the poor diffusion kinetics of K+ seriously affect the electrochemical performance of the battery. Carbon nanofibers (CNFs)-based materials (including CNFs, metal/CNFs composites, chalcogenide/CNFs composites, and other CNFs-based materials) are widely used as PIBs electrode anode materials due to their three-dimensional conductive network, heteroatom doping and excellent mechanical properties. This review discusses in detail the research progress of CNFs-based materials in PIBs, including material preparation, structural design, and performance optimization. On this basis, this article explores the key issues faced by CNFs-based materials and future development directions, and proposes improvement suggestions for providing new ideas for the development of CNFs-based materials.

High-Fidelity, Low-Hysteresis Bionic Flexible Strain Sensors for Soft Machines.

Stretchable flexible strain sensors based on conductive elastomers are rapidly emerging as a highly promising candidate for popular wearable flexible electronic and soft-mechanical sensing devices. However, due to the intrinsic limitations of low fidelity and high hysteresis, existing flexible strain sensors are unable to exploit their full application potential. Herein, a design strategy for a successive three-dimensional crack conductive network is proposed to cope with the uncoordinated variation of the output resistance signal arising from the conductive elastomer. The electrical characteristics of the sensor are dominated by the successive crack conductive network through a greater resistance variation and a concise sensing mechanism. As a result, the developed elastomer bionic strain sensors exhibit excellent sensing performance in terms of a smaller overshoot response, a lower hysteresis (∼2.9%), and an ultralow detection limit (0.00179%). What's more, the proposed strategy is universal and applicable to many conductive elastomers with different conductive fillers (including 0-D, 1-D, and 2-D conductive fillers). This approach improves the sensing signal accuracy and reliability of conductive elastomer strain sensors and holds promising potential for various applications in the fields of e-skin and soft robotic systems.

N atoms regulate heterogeneous crystal phase engineering of mesoporous magnetic FexN nanofibers to promote electromagnetic wave dissipation of magnetic composite aerogel absorbers

One dimensional (1D) soft magnetic nanomaterial and its lightweight porous composites are highly needed in promoting electromagnetic wave absorption for the high-frequency magnetic response and low density. In this study, lightweight magnetic composite aerogels were fabricated through the process of heterogeneous crystal phase, involving the modulation of 1D mesoporous magnetic FexN nanofibers with N atoms. The promotion of electromagnetic wave dissipation was achieved through meticulous composition design and interface optimization. The multi-mode magnetic resonance of 1D heterogeneous crystal FexN magnetic nanofibers, along with the N-doped reduced graphene/amorphous carbon three-dimensional conductive network, greatly enhances electromagnetic wave dissipation through the magnetic-dielectric synergistic effect. Consequently, the resulting composite absorber demonstrates remarkable microwave absorption capabilities, achieving a maximum effective absorption bandwidth (EABmax) of 6.63 GHz at a thickness of 2.13 mm, and a minimum reflection loss (RLmin) of −63.3 dB. In addition, the composite magnetic aerogel with the best microwave absorption performance shows a low density of 11.25 mg/cm3. This electromagnetic synergy approach is anticipated to serve as a guide for the development of highly efficient lightweight magnetoelectric composite for wideband microwave absorption in the future.

A novel strategy to prepare high performance multifunctional composite films by combining electrostatic assembly, crosslinking, topology enhancement and sintering.

Currently, polymer-fiber composite films face the challenge of striking a balance between good mechanical properties and multi-functionalities. Here, aramid fibers (ANFs), chitosan (CS) dendritic particles, and silver nanowires (AgNWs) were used to create high-performance multifunctional composite films. AgNWs and polymer dendritic particles form an interpenetrating segregated network that ensures both a continuous conductive filler and a polymer network. Electrostatic assembly eliminates repulsion between negatively charged ANFs, cross-linked CS particles generate a stable three-dimensional network, and a "brick-mortar" structure composed of multiple materials contributes to topological enhancement. Sintering encourages local overlap and fusing of the AgNWs while reducing their internal flaws. Based on the above strategy, these films achieve a strength of 306.5 MPa, a toughness of 26.5 MJ m-3, and a conductivity of 392 S cm-1. Density functional theory (DFT) and Comsol simulations demonstrate that the introduction of CS thin layers leads to strong hydrogen bonds and three-dimensional continuous conductive networks. With its outstanding mechanical and electrical properties, the AgNW@ANF/CS-CH film demonstrates excellent electromagnetic shielding (22 879.1 dB cm2 g-1) and Joule heating (70 °C within 10 s) capabilities. This work presents a novel approach to fabricate high-performance conductive films and expand their potential applications in lightweight wearable electronics and electrothermal therapy.

Multifunctional strain-activated liquid-metal composite films with electromechanical decoupling for stretchable electromagnetic shielding.

The increasing miniaturization and intelligence of flexible electronic devices pose a challenge to the facile and scalable fabrication of multifunctional stretchable electromagnetic interference (EMI) shielding films with strain-stable shielding effectiveness (SE). This paper presents a highly stretchable liquid metal/thermoplastic polyurethane (LM/TPU) composite film produced via a facile method of scraping and pre-stretching induced activation. The TPU matrix endows the activated LM/TPU (ALMT) film with excellent tensile properties (elongation at break >700%), and the stable and malleable three-dimensional conductive LM network enables the ALMT film to exhibit almost negligible resistance changes and strain-enhanced conductivity during stretching, resulting in excellent strain-insensitive far-field and near-field shielding capabilities. Moreover, the high EMI SE up to ∼60 dB in the tensile state (0-400%) and reduced thickness from ∼75 to ∼50 μm during stretching allow the SE/thickness values of the ALMT film to increase from ∼700 to ∼1200 dB mm-1, outperforming most of the reported LM/polymer composites. Furthermore, the stretchability of the ALMT film provides efficient Joule-heating performance even under substantial deformation, and it can also serve as a strain sensor for real-time monitoring of human motion. The strain-insensitive EMI shielding behavior as well as the outstanding Joule heating and sensing performance of the ALMT film renders it a promising candidate for next-generation flexible electronic devices.

Embedded printing of graphene sponge sensors for sleep monitoring

This study presents an approach for developing sleep monitoring sensors with excellent satisfactory softness, sensitivity and stability by embedding three-dimensional graphene conductive network patterns onto sponges.

Aligned NMC811 electrodes by functionalized conductive graphite flakes for fast-charging Li-ion battery

In recent years, the demand for high capacity, long cycle life, fast charging, and increased safety lithium-ion batteries has become increasingly urgent, especially in the electric vehicle industry. The specific capacity of Li-ion batteries is growing steadily under the great efforts of researchers. However, fast charging, as one of the key technologies of lithium-ion batteries, is still not fully and efficiently resolved. Electric vehicles now have a sufficient driving range, but they take too long to refill compared to traditional vehicles. Here, we aligned polycrystalline NMC 811 microparticles by functionalized graphitic flakes (conductive graphite KS6) under a rotating magnetic field by 2 steps in the cathode fabrication process and constructed an effective and fast conducting three-dimensional conductive network for both electron and ion transport in the cathode system of a high-rate performance Li-ion battery. We successfully regulate and control the tortuosity and porosity of the NMC811 cathode on the electrode level. The new electrode structure has higher ionic conductivity and higher specific capacity. The specific capacity of the electrode with the new electrode structure is about four times and five times the reference electrode at 5 C and at 10 C, respectively. And, the half-cell of the electrode can be fed with 70 % SOC in a 6-min charge at 5 C.

In-situ growing of helical carbon fibers on graphene for high-performance flexible strain sensor

Flexible strain sensors have broad applications in the field of human health monitoring. It is essential to design and manufacture sensors with high sensitivity and stability. The aim could be achieved by constructing multi-level interface structure with non ohmic contact in the flexible three-dimensional conductive network. In this paper, helical carbon fibers (HCF) were grown in situ on the surface of 2D sheet material graphene. The prepared composite conductive material GO/HCF has an excellent 3D structure, significantly enhancing the sensor's sensitivity. PDMS and NH4HCO3 encapsulated strain sensor (GO/HCF/N) has GF values of up to 622.8. Besides, the sensor exhibits unique sensing characteristics that other sensors do not have: under low strain conditions, the resistance of the sensor increases with the increase of deformation, and when the deformation exceeds a certain value, the resistance decreases instead. Therefore, GO/HCF/N sensor has a shallow detection limit (0.1 %) and works steadily after 1000 times tensile release cycles. This flexible strain sensor can quickly and accurately identify different human movements in human health monitoring.

Ultra-stretchable, sensitive and breathable electronic skin based on TPU electrospinning fibrous membrane with microcrack structure for human motion monitoring and self-powered application

With the rapid development of wearable electronic, electronic skin with excellent performance for human motion detection have been widely investigated recently. In this work, a multifunctional electronic skin with three-dimensional conductive network skeleton was prepared based on synergistic conductive filler (carboxylated multi-walled carbon nanotubes (C-MWCNT) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS)) decorated breathable thermoplastic polyurethane (TPU) electrospinning fibrous membrane. Then, microcrack structure was constructed via pre-stretching and the strain sensitivity of the resultant C-MWCNT/PEDOT:PSS/TPU (CPT) conductive fibrous membrane could be effectively adjusted by changing the microcrack density. Due to the three-dimensional conductive network skeleton, microcrack structure and the bridging effect of C-MWCNT between the adjacent crack fragments, ethylene glycol treated CPT (mass ratio of C-MWCNT and PEDOT:PSS is 9/1) (e-CPT9/1) strain sensor exhibited high sensitivity (6008.3), wide response range (680 %), fast response/recovery time (200 ms/200 ms), low detection limit (0.5 %), excellent durability and repeatability (6000 cycles). The excellent strain sensing performances enables it to accurately monitor motion activities and physiological signals, and can also be used as a smart sensing glove to identify different letters gesture and numeric gestures. Furthermore, owing to the photothermal conversion ability and thermoelectric effect of C-MWCNT and PEDOT:PSS, the obtained e-CPT9/1 device also displayed efficient “light-thermal-electric” conversion ability and showed the great potential as self-powered strain sensor.

Bimetallic nitride Co3W3N nanoparticles anchored on ordered N-Doped porous Carbon: An efficient catalyst for oxygen reduction reaction

Carbon-supported transition metal nitrides (TMNs/C) have been considered as promising non-precious metal electrocatalysts toward oxygen reduction reaction (ORR) in both fuel cells and metal–air batteries. However, the development of TMNs/C catalysts with high-performance by using simple and efficient synthesis is still a significant challenge. Here, an in-situ multi-constituents co-assembly strategy was applied to fabricate a novel carbon-supported bimetallic nitride Co3W3N composite, in which Co3W3N nanoparticles (NPs) uniformly anchored in N-doped ordered porous carbon (NPC). Within Co3W3N/NPC composite, the homogeneously dispersed Co3W3N NPs (∼9 nm) combined with N-doping possess highly ORR catalytic activity. its ordered mesoporous structure provides a three-dimensional conductive network and a high surface area (591.9 m2 g−1), which ensures fast electron transport and effective electrolyte infiltration. Due to the superiorities of material and structure, the Co3W3N/NPC served as ORR electrocatalyst shows almost the same excellent electrocatalytic activity with commercial Pt/C in alkaline media. Especially, its durability and methanol-tolerance ability in the ORR process are much better than those of commercial Pt/C. Furthermore, Co3W3N/NPC composite can also be used as cathodic catalyst of Li-O2 battery, which exhibits good rate capability and cycling stability.

Epoxy group and conductive network incorporation effectively enhanced electrochemical performance of MWCNTs/Ca3Co4O9 nanocomposites

Ca3Co4O9 anodes have been intensively investigated due to its high safety and excellent cycling stability. In comparison to the pure Ca3Co4O9, the 9 wt% MWCNTs/Ca3Co4O9 nanocomposite anode exhibited a favorable reversible capacity of 526.6 mAh/g and the excellent charge/discharge capacities of 524.7/507.5 mAh/g after 100th cycles were obtained due to epoxy groups anchoring and the construction of conductive network. The Coulombic efficiencies of all samples were maintained as high as 90 %. More importantly, a continuous three-dimensional (3D) long-range conductive network shortened transport channels for ions/electrons and enhanced the ionic/electronic conductivity. The interfacial resistance (Rs) value of 2.8 Ω was obtained for the 9 wt% MWCNTs/Ca3Co4O9. The improved electrochemical properties of the nanocomposites were attributed to the incorporation of epoxy groups anchoring and much Li+ active sites offering. This novelty route is attractive alternative method for preparing oxides anode materials, which is beneficial to the large capacity and outstanding cycling stability for the applications of high-power Li-ion batteries.

Hybrid crosslinking for in-situ encapsulation of three-dimensional porous SiOx@rGO as high-performance anodes in lithium-ion batteries

Silicon suboxide (SiOx) anodes have garnered significant attention from both academia and industry due to their superior theoretical capacity compared to graphite, as well as their improved capacity retention in comparison to pure silicon. Nevertheless, SiOx electrodes still confront the challenge of substantial volume expansion (>160 %) during the alloying process, resulting in electrode structural damage or even fragmentation and severely impacting cycling performance. Here, a three-dimensional (3D) conductive network was constructed by ethylenediamine (EDA) cross-linking reduced graphene oxide (rGO), which was encapsulated on the surface of SiOx spheres generated in situ via a magnesium thermal reduction reaction. Accordingly, the SiOx@rGO-EDA anode was prepared successfully with high reversible capacity (892 mAh g−1 after 100 cycles at 1 A g−1) and fascinating rate performance (447 mAh g−1 at 4 A g−1). In full cell, the SiOx@rGO-EDA anode also exhibits outstanding cycling stability (154 mAh g−1 after 100 cycles at 0.1C) and rate capability. The scanning electron microscopy (SEM) images captured from a top-view perspective indicate that the surface of SiOx@rGO-EDA electrode is smooth and dense without any noticeable cracks, and it maintains its structural integrity throughout the cycling process. The cross-sectional thickness of the electrode remains essentially the same. These results illustrate the superior structural stability of the EDA cross-linked graphene conductive network cladding structure, enabling it to adapt to dynamic changes and ensure efficient transport of lithium ions and electrons. The facile and versatile synthesis method of SiOx@rGO-EDA structures by incorporating cross-linking agents provides inspiration for the design of next-generation high-performance anodes.

Fe-single-atom catalyst nanocages linked by bacterial cellulose-derived carbon nanofiber aerogel for Li-S batteries

Li-S battery (LSB) is promising for achieving high capacity. Still, its development is hindered by the complex redox process with sluggish kinetics and particularly the resulting lithium polysulfides (LiPS) shuttle effects. Single-atom catalysts (SACs), with their maximized atom utilization, could effectively chemisorb soluble LiPSs and expedite the sulfide conversion reaction kinetics. Here we report incorporating Fe single metal atom catalyst (Fe-SAC) in the sulfur cathode design and its electrocatalytic effects. Fe-doped ZIF-8 nanocages were introduced into a cheap biomass bacteria cellulose. A pyrolysis process converted them into an aerogel structure with Fe-SAC-functionalized N-doped carbon nanocages linked by a carbon nanofiber network (FeSA-NC@CBC), which was applied as a scaffold to fabricate freestanding and binder-free sulfur cathodes. We conducted electrochemical measurements to reveal Fe-SAC functions including lowering energy barriers for S8 reduction to liquid-phase LiPSs and further to solid-phase Li2S2/Li2S and accelerating Li2S2/Li2S nucleation and deposition, as corroborated by our theoretical calculation results. Benefiting from the synergistic effects of highly active Fe-SAC and three-dimensional conductive network, the sulfide reaction kinetics is improved, which can diminish LiPS shuttle effects and therefore improve LBS rate performance and cycling stability. Accordingly, the fabricated FeSA-NC@CBC composite cathode delivers an excellent rate capability at 2C with a reversible capacity of 840 mAh/g and a long-term cyclic stability of 800 mAh/g at 1C after 500 cycles.

Nanoflower-like hollow NiMnCo-OH decorated with self-assembled 2D Ti3C2Tx for high-efficiency hybrid supercapacitors

Layered double hydroxides (LDHs) have gained awareness as promising energy materials due to their high electrochemical activity and tunable interlayer characteristics. However, inherent drawbacks limit them to achieve high capacitance. Introducing complementors with high conductivity and stability is an effective strategy for addressing these challenging issues. Therefore, we employed a simple and controllable method to synthesize nanoflower-like hollow NiMnCo-OH@MXene (NMCM) composites by multi-element doping and electrostatic self-assembly strategies. The MXene nanosheets formed a three-dimensional (3D) conductive network, which increased stability and promoted fast charge transport at interfaces. At the same time, the heterogeneous ternary hydroxides inhibited MXene aggregation and provided considerable capacitance. The NMCM showed ultra-long cycling stability of 91.7% after 5000 cycles at 5 A g−1 (compared to the initial specific capacitance) and achieved a capacitance capacity of 232.37 mAh g−1 at 1 A g−1 in a three-electrode device. Furthermore, under 800 W kg−1 power density, the NMCM//Ti3C2 asymmetric device showed an impressive energy density of 54.1 Wh kg−1. This work demonstrates a simple and successful strategy for creating high-performance energy storage devices based on 3D hollow framework electrodes.

Face-to-face conducting mechanism enabled by Si-C bonds for binder free Si@CNTs electrode

The three-dimensional conductive network has been developed, creating a continuous pathway for Si anodes. Nonetheless, the weak physical contact between Si particles and the conducting network is prone to separation due to expansion stress and the solid electrolyte interface. This results in a rapid decline in cell cycling performance. Herein, we have developed a binder free Si@CNTs fibrous thin film structure using carbon nanotube (CNT) conducting networks through a high vacuum magnetic sputtering process of molecular reorganization. With Fourier Transform Infrared (FTIR), X-ray Photoelectron Spectroscopy (XPS) tests and density functional theory (DFT) calculations, we propose a strong “face-to-face” contact configuration based on Si-C bonds. The Si@CNTs film demonstrated stable mechanical and electrical properties even after repeated bending and stretching of up to 6%. In-situ transmission electron microscopy confirmed that the initial cycling volume expansion of the Si@CNTs fibers with Si-C bonds was only 58.33%. Furthermore, the full cell using Si@CNTs anode enabled stable high-rate cycling performance at 6C after 500 cycles. This innovative strategy redefines the conductive mode of CNTs with Si anodes.

Construction of three-dimensional conductive network and heterogeneous interfaces via different ratio for tunable microwave absorption

Construction of three-dimensional conductive network and heterogeneous interfaces via different ratio for tunable microwave absorption

Binary Transition-Metal Sulfides/MXene Synergistically Promote Polysulfide Adsorption and Conversion in Lithium-Sulfur Batteries.

Currently, severe shuttle effects and sluggish conversion kinetics are the main obstacles to the advancement of lithium-sulfur (Li-S) batteries. Modification of the battery separator by a catalyst is a promising approach to tackle these problems, but simultaneously obtaining rich catalytic active sites, high conductivity, and remarkable stability remains a great challenge. Herein, a flower-like MXene/MoS2/SnS@C heterostructure as the functional intercalation of Li-S batteries was prepared for accelerating the synergistic adsorption-electrocatalysis of sulfur conversion. The MXene skeleton constructs a three-dimensional conductive network that anchors polysulfides and enhances charge transfer. Meanwhile, the MoS2/SnS has rich active sites for accelerating polysulfide conversion, leading to excellent electrochemical performances. A battery with MXene/MoS2/SnS@C displays an extraordinary capacity of 836.1 mAh g-1 over 200 cycles at 0.5C and demonstrates a remarkable cycling stability with a capacity attenuation of approximately 0.051% per cycle during 1000 cycles at 2C. When the sulfur loading reaches 5.1 mg cm-2, the capacity still maintains 722.4 mAh g-1 over 50 cycles. This research proposes a novel strategy to design stable catalysts for Li-S batteries with an extended lifespan.