Tunable Electrical Conductivity Research Articles

A new approach for preparation of metal-containing polyamide/carbon textile laminate composites with tunable electrical conductivity

Multiscale thermoplastic laminate composites based on polyamide 6 (PA6) dually reinforced by carbon fiber woven textile structures (CFT) and different micron-sized metal particles are prepared for the first time by microencapsulation strategy. In a first step, activated anionic ring-opening polymerization (AAROP) of e-caprolactam is carried out in suspension, in the presence of different metal particles, to produce shell-core PA6 microcapsules (PAMC) loaded with 13–19% metal. In a second step, the loaded PAMC are distributed between CFT plies with fiber volume fractions V f = 0.25 or V f = 0.50 and then the ply arrays are consolidated by compression molding. Separately, metal-loaded PA6 hybrid composites are prepared by direct compression molding of PAMC and used to compare their properties to the CFT-metal laminates. Light- and scanning electron microscopy are used to study the morphology and the interfaces between the fillers and the polymeric matrix. These structural results are related to the mechanical behavior in tension and the electrical properties. A notable increase of the d.c. electrical conductivity in 7 orders of magnitude is observed for the CFT-metal laminates with respect to the neat PA6. This increase is accompanied by a 2.5–3.0 times growth of the Young’s modulus and of the strength at break. It is concluded that the microencapsulation strategy can be applied to produce multifunctional CFT-metal-PA6 thermoplastic composites with tailored electrical and improved mechanical properties for advanced applications.

Aqueous Nanocoating Approach to Strong Natural Microfibers with Tunable Electrical Conductivity for Wearable Electronic Textiles

Electronically conductive and mechanically strong natural fibers with desirable durability, flexibility, and environmental compatibility are in great need for manufacturing multifunctional textiles. Here we reveal a facile yet effective nanocoating approach to immobilization of few-layer graphene oxide (GO) nanosheets at ramie fiber by hydrogen-bond-driven self-assembly process under all-aqueous and additive-free condition. The surface morphology and chemistry of GO-functionalized ramie fiber (GOFR) were significantly altered with the homogeneous decoration of trace amount of GO nanosheets, readying remarkable property improvements and functionality realization. The tensile strength of GOFR (553 MPa) witnessed an increase of over 25% compared to pristine ramie, as accompanied by moderate promotion of extensibility with the assistance of robust GO nanosheets. It is worth noting that exceptionally high electrical conductivity was achieved for thermally reduced GOFR (rGOFR), with values as high as 83.2 S/cm ...

Tunable conductivity in mesoporous germanium

Germanium-based nanostructures have attracted increasing attention due to favourable electrical and optical properties, which are tunable on the nanoscale. High densities of germanium nanocrystals are synthesized via electrochemical etching, making porous germanium an appealing nanostructured material for a variety of applications. In this work, we have demonstrated highly tunable electrical conductivity in mesoporous germanium layers by conducting a systematic study varying crystallite size using thermal annealing, with experimental conductivities ranging from 0.6 to 33 (×10−3) Ω−1 cm−1. The conductivity of as-prepared mesoporous germanium with 70% porosity and crystallite size between 4 and 10 nm is shown to be ∼0.9 × 10−3 Ω−1 cm−1, 5 orders of magnitude smaller than that of bulk p-type germanium. Thermal annealing for 10 min at 400 °C further reduced the conductivity; however, annealing at 450 °C caused a morphological transformation from columnar crystallites to interconnecting granular crystallites and an increase in conductivity by two orders of magnitude relative to as-prepared mesoporous germanium caused by reduced influence of surface states. We developed an electrostatic model relating the carrier concentration and mobility of p-type mesoporous germanium to the nanoscale morphology. Correlation within an order of magnitude was found between modelled and experimental conductivities, limited by variation in sample uniformity and uncertainty in void size and fraction after annealing. Furthermore, theoretical results suggest that mesoporous germanium conductivity could be tuned over four orders of magnitude, leading to optimized hybrid devices.

Tailoring the Porosity and Microstructure of Printed Graphene Electrodes via Polymer Phase Inversion

Phase inversion is demonstrated as an effective method for engineering the microstructure of graphene films by exploiting the well-defined solubility characteristics of polymer dispersants. Drying of a tailored phase inversion ink containing a nonvolatile nonsolvent leads to gelation and subsequent pore formation, providing a promising strategy to tailor the porosity of the resulting graphene films. Graphene films with tunable porosity and electrical conductivity ranging from ∼1000 to ∼22 000 S/m are fabricated by this method. Moreover, this dry phase inversion technique is compatible with conventional coating and printing methods, allowing direct ink writing of porous graphene microsupercapacitor electrodes for energy storage applications. Overall, this method provides a straightforward and versatile strategy for engineering the microstructure of solution-processed nanomaterials.

Direct 3D Printing of Ultralight Graphene Oxide Aerogel Microlattices

AbstractGraphene aerogel microlattices (GAMs) hold great prospects for many multifunctional applications due to their low density, high porosity, designed lattice structures, good elasticity, and tunable electrical conductivity. Previous 3D printing approaches to fabricate GAMs require either high content of additives or complex processes, limiting their wide applications. Here, a facile ion‐induced gelation method is demonstrated to directly print GAMs from graphene oxide (GO) based ink. With trace addition of Ca2+ ions as gelators, aqueous GO sol converts to printable gel ink. Self‐standing 3D structures with programmable microlattices are directly printed just in air at room temperature. The rich hierarchical pores and high electrical conductivity of GAMs bring admirable capacitive performance for supercapacitors. The gravimetric capacitance (Cs) of GAMs is 213 F g−1 at 0.5 A g−1 and 183 F g−1 at 100 A g−1, and retains over 90% after 50 000 cycles. The facile, direct 3D printing of neat graphene oxide can promote wide applications of GAMs from energy storage to tissue engineering scaffolds.

Recent progress on nanostructured conducting polymers and composites: synthesis, application and future aspects

Conducting polymers (CPs) have been widely investigated due to their extraordinary advantages over the traditional materials, including wide and tunable electrical conductivity, facile production approach, high mechanical stability, light weight, low cost and ease in material processing. Compared with bulk CPs, nanostructured CPs possess higher electrical conductivity, larger surface area, superior electrochemical activity, which make them suitable for various applications. Hybridization of CPs with other nanomaterials has obtained promising functional nanocomposites and achieved improved performance in different areas, such as energy storage, sensors, energy harvesting and protection applications. In this review, recent progress on nanostructured CPs and their composites is summarized from research all over the world in more than 400 references, especially from the last three years. The relevant synthesizing experiences are outlined and abundant application examples are illustrated. The approaches of production of nanostructured CPs are discussed and the efficacy and benefits of newest trends for the preparation of multifunctional nanomaterials/nanocomposites are presented. Mechanism of their electrical conductivity and the ways to tailor their properties are investigated. The remaining challenges in developing better CPs based nanomaterials are also elaborated.

Porous Graphene Microflowers for High-Performance Microwave Absorption

Graphene has shown great potential in microwave absorption (MA) owing to its high surface area, low density, tunable electrical conductivity and good chemical stability. To fully realize grapheneʼs MA ability, the microstructure of graphene should be carefully addressed. Here we prepared graphene microflowers (Gmfs) with highly porous structure for high-performance MA filler material. The efficient absorption bandwidth (reflection loss ≤ −10 dB) reaches 5.59 GHz and the minimum reflection loss is up to −42.9 dB, showing significant increment compared with stacked graphene. Such performance is higher than most graphene-based materials in the literature. Besides, the low filling content (10 wt%) and low density (40–50 mg cm−3) are beneficial for the practical applications. Without compounding with magnetic materials or conductive polymers, Gmfs show outstanding MA performance with the aid of rational microstructure design. Furthermore, Gmfs exhibit advantages in facile processibility and large-scale production compared with other porous graphene materials including aerogels and foams.

Fabrication of Graphene-Polyimide Nanocomposites with Superior Electrical Conductivity.

We report on the fabrication of a novel class of lightweight materials, polyimide-graphene nanocomposites (0.01-5 vol %), with tunable electrical conductivity. The graphene-polyimide nanocomposites exhibit an ultra-low graphene percolation threshold of 0.03 vol % and maximum dc conductivity of 0.94 S/cm, which we attribute to excellent dispersion, extraordinary electron transport in the well-dispersed graphene, high number density of graphene nanosheets, and the π-π interactions between the aromatic moieties of the polyimide and the carbon rings in graphene. The dc conductivity data are shown to follow the power-law dependence on the graphene volume fraction near the percolation threshold. The ac conductivity of the nanocomposites is accurately represented by the extended pair-approximation model. The exponent s of the approximation is estimated to be 0.45-0.61, indicating anomalous diffusion of charge particles and a fractal structure for the conducting phase, lending support to the percolation model. Low-temperature dc conductivity of the nanocomposites is well-approximated by the thermal fluctuation-induced tunneling. Wide-angle X-ray scattering and transmission electron microscopy were utilized to correlate the morphology with the electrical conductivity. The lack of maxima in X-ray indicates the loss of structural registry and short-range ordering.

The effect of rare earth ions on structural, morphological and thermoelectric properties of nanostructured tin oxide based perovskite materials

Metal oxide based materials are promising for thermoelectric applications especially at elevated temperature due to their high thermal stability. Recently, perovskite based oxide materials have been focused as a novel thermoelectric material due to their tunable electrical conductivity. Thermoelectric properties of BaSnO3 has been extensively investigated. However, the effect of various rare earth doping on the thermoelectric properties of BaSnO3 is not studied in detail. In the present work, Ba1−xRExSnO3 (RE = La and Sr) materials with x = 0.05 were prepared by polymerization complex (PC) method in order to study the effect of RE incorporation on the structural, morphological and thermoelectric characteristics of BaSnO3. The structural and morphological properties of the synthesized materials were studied by XRD and TEM analysis. XRD analysis confirmed the mixed phases of the synthesized samples. The TEM images of Ba1−xSrxSnO3 shows hexagonal and cubic morphology while, Ba1−xLaxSnO3 exhibit rod like morphology. Various functional groups of the perovskite material were identified using FTIR analysis. Formation of the perovskite material was further confirmed by XPS analysis. The Seebeck coefficient of Ba0.95La0.05SnO3 was relatively higher than that of Ba0.95Sr0.05SnO3, especially at high temperature. The rod like morphology of Ba0.95La0.05SnO3 may facilitate fast electron transport which results high thermal power compared to Ba0.95Sr0.05SnO3 despite of its poor crystalline nature. The substitution of La3+ on the Ba2+ site could vary the carrier density which results high Seebeck coefficient of Ba0.95La0.05SnO3 compared to Ba0.95Sr0.05SnO3. From the experimental results, it is obvious that Ba0.95La0.05SnO3 could be a promising thermoelectric material for high temperature application.

Buckypaper Supported Pt Monolayers Catalyst for PEM Applications

Buckypaper supported Pt monolayers catalyst for PEM applications Low temperature fuel cells such as polymer exchange membrane (PEM) or solid-acid fuel cells (SAFCs) typically utilize Pt materials as the catalyst of choice. Lowering the loading of Pt while ensuring its service life remain two major goals for lowering the cost barriers to the commercialization of these fuel cells. In addition, compacting the design of fuel cells for non-stationary applications (e.g. vehicles), while increase the output power density is a desirable achievement for a more efficient fuel cell. Conductive carbon is the current low-cost option as the catalyst support but carbon corrosion continues to be an impediment to the long-term stability of the catalyst systems in fuel cells. Carbon Nanotubes (CNT) possess high specific surface area, mechanical robustness, good tunable electrical conductivity and inertness against most of chemicals, especially acids. Over the past decade, there has been a growing interest in trying to incorporate CNT-based materials as catalyst supports especially in cases where scale-up to mass production is viable. Buckypaper, as an ultrathin mesh of aggregated CNTs can be produced in a roll-to-roll fashion for several meters, while maintaining a highly porous structure with specific surface area of hundreds meter squares per gram of CNT. In addition, their chemistry can be changed from pristine to super hydrophobic to hydrophilic through chemical functionalization of CNT. The inherent properties of CNT, its catalytic applications, high surface area and facile fabrication of buckypaper inspired us to explore the efficacy of using a few monolayers of Pt supported on buckypaper as a catalyst architecture for fuel cells. Herein, following a Surface Limited Redox Replacement (SLRR) few monolayers (MLs) of Pt are grown electrochemically on top of a stand-alone buckypaper. Pt thickness is controlled systematically through under potential deposition iterations and the growth was monitored by cyclic voltammetry (CV) scans. Pt MLs wet the CNT ribbons of the buckypaper, while avoiding agglomeration. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) analysis show that surface-utilization is efficient, as Pt is successively deposited not only on the near surface CNTs, but down to the bulk of buckypaper. In addition, XPS analysis shows that the Pt_MLs are in their metallic state, thus confirming successful SLRR rather than eletroless deposition (where some cationic Pt would be expected). Catalyst longevity under processing conditions is a crucial factor to determine the lifetime of fuel cell and its price, which affects its commercialization directly. Department of Energy (DOE) sets a testing protocol to test catalyst activity loss under electrochemical testing. DOE protocols’ target to save 60% of the catalyst activity by 30,000 testing cycles. Our Pt_MLs/buckypaper catalysts show promising results, while saving 50% of the catalyst activity as shown through linear sweep voltammetry (LSV) currents for oxygen reduction reaction (ORR). Raman analysis shows no alteration of CNT G and 2D bands after 30,000 testing cycles, in comparison to Raman spectra of the same sample set before testing, which indicates no carbon corrosion. In conclusion, no carbon corrosion is observed for CNT after long testing (i.e. 30,000 cycles). In addition, power density of Pt MLs catalysts is enhanced by wetting-ability of Pt to the buckypaper throughout its internal 3D porous structure. Moreover, buckypaper shows high susceptibility to Pt interfacial adhesion, and the interfacial interaction between Pt and CNT surface helps to retain Pt atoms as 2D film without ripening. Catalyst activity retained after 30,000 testing cycles is ~ 50%. This initial result promises with more enhancement for power density and catalyst lifetime with chemical functionalization of CNTs in our future work.

Tunable Electrical Conductivity of Carbon-Black-Filled Ternary Polymer Blends by Constructing a Hierarchical Structure.

A type of hierarchical structured composite composed of a minor thermoplastic polyurethane (TPU) phase spreading at the interface of two major phases polyoxymethylene/polyamide copolymer (POM/COPA) and carbon black (CB) particles selectively localized at the TPU/COPA interface of the tri-continuous blends was fabricated by melt compounding. The hierarchical structure was designed according to predictions and verified by a combination of electron microscopy and solvent extraction technique. The hierarchical structured composites show the dramatically decreased percolation threshold, a reduction of 60% compared to those without TPU where CB is selectively distributed in the COPA phase. The effects of CB contents and TPU on the phase morphology of POM/COPA were investigated, showing the occurrence of the POM/COPA phase inversion from a sea-island to a co-continuous structure beyond the percolation threshold of CB in the presence of TPU. The mechanism for the formation of conductive network is construction of CB network at the TPU/COPA interface of tri-continuous POM/COPA/TPU blends and double percolation effect.

Tunable electrical conductivity of polystyrene/polyamide-6/carbon nanotube blend nanocomposites via control of morphology and nanofiller localization

The electrical conductivity and percolation behavior of polymer blend nanocomposites were investigated asa consequence of polymer-filler interaction and blend morphology. The nanocomposites were derived from melt compounding of carbon nanotubes (CNTs) in polystyrene (PS)/polyamide 6 (PA6) blends. The electrical conductivity of co-continuous PS/PA6 (50/50) blends remained constant in the semi-conductive region (6.75×10−8–1.50×10−7S·cm−1) over a wide range of CNT loading (0.5–3.5 phr). Nevertheless, (50/50) blends presented higher electrical conductivity than PA6/CNT nanocomposites with the same effective CNT concentration. Contrary to common intuitions, at high loadings of CNTs, higher electrical conductivity was observed for the blends wherein the CNT-rich PA6 phase was in the form of dispersed droplet morphology rather than co-continuous one. For instance, at the CNT loading of 3.5 phr, the conductivity of blend with PS/PA6 volume ratio of (90/10) is approximately 4 orders of magnitude higher than co-continuous (50/50) blend. This observation is attributed to a two-level percolation mechanism (primary and secondary), as verified by optical and transmission electron microscopy. The primary percolation occurs by selective localization of CNTs in PA6 droplets due to their thermodynamic affinity for the PA6 phase. Once the PA6 droplets are impregnated with CNTs, the excess CNTs (at high loadings) localize in the PS phase and act as effective electrical bridges for the highly conductive PA6 droplets (secondary percolation).

Epoxy–carbon black composite foams with tunable electrical conductivity and mechanical properties: Foaming improves the conductivity

ABSTRACTIn this study, conductive epoxy foams with different carbon black (CB) contents were fabricated with expandable microspheres as foaming agents. The effect of the CB content, microsphere concentration, precuring time, and foaming temperature on the electrical conductivity and compressive properties of the obtained foams were investigated systematically. The differential scanning calorimeter and rheological tests confirmed that the CB accelerated the curing reaction, increased the onset viscosity of the epoxy blend during foaming, and affected the foaming process. In addition, all of the parameters, including the CB content, microsphere concentration, precuring time, and foaming temperature, were confirmed to change the foam structures and further change the conductivity and mechanical properties. The electrical properties test revealed that the foaming process improved the conductivity of the composites. On the basis of the electrical properties test results and scanning electron microscope images, a flow‐induced CB aggregation mechanism is presented, in which the thermally triggered microsphere expansion pushed the resins away, squeezed the CB together, and changed the CB distribution throughout the foams. This made more conductivity paths. The obtained foam could just be used as an antistatic material, but it gave us an example for exploring lightweight and low‐cost conductive epoxy foams with other applications, for example, electromagnetic shielding. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45071.

Low percolation threshold and electromagnetic shielding effectiveness of nano-structured carbon based ethylene methyl acrylate nanocomposites

Abstract In the present work, we developed industrially scalable and affordable Ketjen carbon black (K-CB)-ethylene methyl acrylate copolymer (EMA) composites with low percolation threshold and efficient electromagnetic interference (EMI) shielding efficiency associated with high potential of absorption dominance of electromagnetic (EM) radiations by conductive dissipation. The dispersion and distribution of K-CB inside the EMA elastomer have been affirmed with the help of qualitative electron micrograph techniques. The EMA matrix and K-CB filler interactions have been corroborated through bound rubber content and dynamic mechanical properties. Interfacial interactions between K-CB and polymer matrix are pivotal in determining the good reinforcing efficiency with tunable electrical conductivity as well as adjustable EMI shielding ability in K-CB filled composites. The proposed composites lead to a low percolation threshold (8.6 wt%) and promising high EMI shielding value of 33.9 dB for 20 wt% K-CB in the X-band frequency as compared to other expensive carbon fillers. On account of the thorough analysis of the composites, our high hopes have been placed on the promotion of low budget and flexible EMA/K-CB composite for the emerging field of superior EMI shielding applications.

Growth of Polyaniline Nanoneedles on MoS2 Nanosheets, Tunable Electroresponse, and Electromagnetic Wave Attenuation Analysis

The purpose of this work was to fabricate high-performance dielectric materials for electrorheological (ER) application and electromagnetic (EM) wave attenuation. Commercial MoS2 bulks were exfoliated into nanosheets via combination of ball-milling and bath sonication procedures, which were used as the template for in situ grafting of PANI nanoneedles (PANI-NDs) to afford MoS2/PANI-NDs. The length–diameter (L/D) ratio of PANI-NDs on MoS2 nanosheets was feasibly tuned via modulating the polymerization time. Therefore, the tunable electrical conductivity and dielectric properties of the obtained MoS2/PANI-NDs were achieved. Compared with bare MoS2 nanosheets, MoS2/PANI-ND-based ER fluids constructed more robust fibril-like structure governed by the external electric energy and exhibited higher dynamic yield stress (186.8 Pa at 3 kV/mm) with wider applied electric field strength (0–3.0 kV/mm). Furthermore, as a novel EM wave absorbing material, the maximum reflection loss (RL) values of MoS2 nanosheets reach...

Easily fabricated and lightweight PPy/PDA/AgNW composites for excellent electromagnetic interference shielding.

Conductive polymer composites (CPCs) containing nanoscale conductive fillers have been widely studied for their potential use in various applications. In this paper, polypyrrole (PPy)/polydopamine (PDA)/silver nanowire (AgNW) composites with high electromagnetic interference (EMI) shielding performance, good adhesion ability and light weight are successfully fabricated via a simple in situ polymerization method followed by a mixture process. Benefiting from the intrinsic adhesion properties of PDA, the adhesion ability and mechanical properties of the PPy/PDA/AgNW composites are significantly improved. The incorporation of AgNWs endows the functionalized PPy with tunable electrical conductivity and enhanced EMI shielding effectiveness (SE). By adjusting the AgNW loading degree in the PPy/PDA/AgNW composites from 0 to 50 wt%, the electrical conductivity of the composites greatly increases from 0.01 to 1206.72 S cm-1, and the EMI SE of the composites changes from 6.5 to 48.4 dB accordingly (8.0-12.0 GHz, X-band). Moreover, due to the extremely low density of PPy, the PPy/PDA/AgNW (20 wt%) composites show a superior light weight of 0.28 g cm-3. In general, it can be concluded that the PPy/PDA/AgNW composites with tunable electrical conductivity, good adhesion properties and light weight can be used as excellent EMI shielding materials.

Assembly of 1D coaxial nanoribbons into 2D multicolor luminescence array membrane endowed with tunable anisotropic electrical conductivity and magnetism via electrospinning

A flexible 2D color-tunable coaxial nanoribbon array membrane with anisotropic electrical conductivity and magnetism is successfully fabricated via one-pot electrospinning.

Synthetic Biogenesis of Bacterial Amyloid Nanomaterials with Tunable Inorganic-Organic Interfaces and Electrical Conductivity.

Amyloids are highly ordered, hierarchal protein nanoassemblies. Functional amyloids in bacterial biofilms, such as Escherichia coli curli fibers, are formed by the polymerization of monomeric proteins secreted into the extracellular space. Curli is synthesized by living cells, is primarily composed of the major curlin subunit CsgA, and forms biological nanofibers with high aspect ratios. Here, we explore the application of curli fibers for nanotechnology by engineering curli to mediate tunable biological interfaces with inorganic materials and to controllably form gold nanoparticles and gold nanowires. Specifically, we used cell-synthesized curli fibers as templates for nucleating and growing gold nanoparticles and showed that nanoparticle size could be modulated as a function of curli fiber gold-binding affinity. Furthermore, we demonstrated that gold nanoparticles can be preseeded onto curli fibers and followed by gold enhancement to form nanowires. Using these two approaches, we created artificial cellular systems that integrate inorganic-organic materials to achieve tunable electrical conductivity. We envision that cell-synthesized amyloid nanofibers will be useful for interfacing abiotic and biotic systems to create living functional materials..

Photoresist-assisted fabrication of thermally and mechanically stable silver nanowire-based transparent heaters

Networked structures of percolated silver nanowires (AgNWs) are an important substitute for brittle indium tin oxide (ITO)-based transparent electrodes, owing to their high ductility and tunable optical and electrical conductivities. Recently, AgNWs have been used in the fabrication of flexible transparent heaters, but only when firmly adhered to the underlying polymer substrate so that the electrodes are reliably flexible. Another requirement is that these electrodes must be passivated from the atmosphere, preserving them even when the fabricated heaters are biased at high voltages or exposed to harsh environments. Here, we used conventional photolithography with a coating of commercial photoresist, UV exposure and development, in order to make protected AgNW networks. For this, AgNW networks preformed on a transparent polymer were used as a photomask layer, so that the photoresist could be developed to be selectively present on the AgNWs. As a result of this simple approach, the mechanical/thermal stability and heating performance of our AgNWs-based transparent heaters were successfully enhanced. It displays an increase of <2% in Rs when bent to a radius of 500μm for 10,000 cycles, and a biasing voltage to the heater rapidly increased its temperature above 160°C within a very short time period.

(Invited) Nanostructured Graphene Electrodes for High Performance and Stretchability

Chemically derived graphene oxide (GO) and its derivatives are promising candidates for a variety of carbon-based functional nanostructures and hybrid architectures, because of their unique characteristics that include high theoretical surface area, tunable electrical conductivity, excellent solution processability, and high mass producibility at low cost. However, the irreversible stacking due to the strong π–π interactions between graphene nanosheets during drying or reduction processes significantly decreases the solution processability as well as accessible surface area. In this talk, I firstly present a sea-urchin-shaped template approach for fabricating highly crumpled graphene balls in bulk quantities with a simple process. Simultaneous chemical etching and reduction process of graphene oxide (GO)-encapsulated iron oxide particles results in dissolution of the core template with spiky morphology and conversion of the outer GO layers into reduced GO layers with increased hydrophobicity which remain in contact with the spiky surface of the template. After completely etching, the outer graphene layers are fully compressed into the crumpled form along with decrease in total volume by etching. The crumpled balls exhibit significantly larger surface area and good water-dispersion stability than those of stacked reduced GO or other crumple approaches, even though they also show comparable electrical conductivity. Furthermore, they are easily assembled into 3D macroporous networks without any binders through typical processes such as solvent casting or compression molding. The graphene networks with less pore volume still have the crumpled morphology without sacrificing the properties regardless of the assembly processes, producing a promising active electrode material with high gravimetric and volumetric energy density for capacitive energy storage. For the second part, using a facile ice-templated self-assembly process with reduced graphene sheets and vanadium phosphate (VOPO4) nanosheets, we realize a vertically porous nanocomposite of layered VOPO4 and graphene nanosheets with high surface area and high electrical conductivity. The resulting 3D VOPO4–graphene nanocomposite has a much higher capacitance of 527.9 F g–1 at a current density of 0.5 A g–1, compared with ~247 F g–1 of simple 3D VOPO4, with solid cycling stability. The enhanced pseudocapacitive behavior mainly originates from vertically porous structures from directionally grown ice crystals and simultaneously inducing radial segregation and forming inter-stacked structures of VOPO4–graphene nanosheets. This VOPO4–graphene nanocomposite electrode exhibits high surface area, vertically porous structure to the separator, structural stability from interstacked structure and high electrical conductivity, which would provide the short diffusion paths of electrolyte ions and fast transportation of charges within the conductive frameworks. In addition, an asymmetric supercapacitor (ASC) is fabricated by using vertically porous VOPO4–graphene as the positive electrode and vertically porous 3D graphene as the negative electrode; it exhibits a wide cell voltage of 1.6 V and a largely enhanced energy density of 108 Wh kg–1. In the last part, we also used the ice-templated vertically porous graphene nanostructures as a stretchable supercapacitor electrode. Radially compressed honeycomb structures exhibited nearly-zero poission ratio structures and maintained their structure and electrical conductivity even at 50 % of starched states. The capacitive performance of these compressed honeycomb structures also shows fairly high over 130 F g-1 and these high performance still be maintained at highly stretched condition.