[Show abstract][Hide abstract] ABSTRACT: Polyelectrolytes have garnered significant attention as a key electrochemically-active component in a diversity of energy-related industry fields. Among enormous efforts to develop advanced polyelectrolytes, blending of different polyelectrolyte mixtures is suggested as a facile and efficient way. However, unavoidable thermodynamic immiscibility between the blend components has often caused serious challenges in the versatile fabrication of polyelectrolyte blends with desirable membrane properties. Here, as an unprecedented mixing strategy to address this issue, we demonstrate a new class of dual electrospray (DES)-assisted forced polymer blending. As a model system to explore the feasibility of this blending approach, Nafion and multiblock sulfonated hydrocarbon copolymer (denoted as sBlock) comprising sulfonated hydrophilic poly(arylene thioether sulfone) blocks and hydrophobic poly(arylene ether sulfone) blocks are chosen. The processing uniqueness and simplicity of the DES blending technique enable the successful fabrication of Nafion/sBlock blends (referred to as N/B blends) that are difficult to achieve with conventional blending methods due to their large miscibility difference. More notably, during the DES blending, nonsolvent-induced nanophase morphology reconstruction occurs in the N/B Blend, eventually giving rise to some difference in proton conductivity between experimental values and theoretically predicted ones. We envision that the DES-assisted forced blending strategy holds a great deal of promise as a versatile and scalable manufacturing technology to breakthrough the deadlock of thermodynamically immiscible polymer blends and also can be easily applicable to a wide variety of polymer blend systems.
[Show abstract][Hide abstract] ABSTRACT: We describe the in situ synthesis of the covalent organic framework-5 (COF-5) on the surfaces of carbon nanotubes (CNTs) and graphenes having homogeneous CNT@COF-5 core-shell structures using a sonochemical reaction in one pot. CNT@COF-5 was found to show better CO2 adsorption than the pristine COF-5.
[Show abstract][Hide abstract] ABSTRACT: Understanding and control of interfacial phenomena between electrode material and liquid electrolytes are of major scientific importance for boosting development of high-performance lithium ion batteries with reliable electrochemical/safety attributes. Here, as an innovative surface engineering approach to address the interfacial issues, a new concept of mixed ion/electron-conductive soft nanomatter-based conformal surface modification of the cathode material is presented. The soft nanomatter is comprised of an electron conductive carbonaceous (C) substance embedded in an ion conductive polyimide (PI) nanothin compliant film. In addition to its structural uniqueness, the newly proposed surface modification benefits from a simple fabrication process. The PI/carbon soft nanomatter is directly synthesized on LiCoO2 surface via one-pot thermal treatment of polyamic acid (=PI precursor) and sucrose (=carbon source) mixture, where the LiCoO2 powders are chosen as a model system to explore the feasibility of this surface engineering strategy. The resulting PI/carbon coating layer facilitates electronic conduction and also suppresses unwanted side reactions arising from the cathode material-liquid electrolyte interface. These synergistic coating effects of the multifunctional PI/carbon soft nanomatter significantly improve high-voltage cell performance and also mitigate interfacial exothermic reaction between cathode material and liquid electrolyte.
Journal of Power Sources 10/2014; 263:209–216. DOI:10.1016/j.jpowsour.2014.04.028 · 6.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Considerable attention has focused on the combination of carbon nanotubes (CNTs) and metal-organic frameworks (MOFs) since both nanomaterials have outstanding properties. We describe a method for the homogeneous decoration of an MOF (ZIF-8 was chosen) onto the surfaces of CNTs dispersed by polyvinylpyrrolidones (PVPs) in methanol, which was revealed by a scanning electron microscopic study. The homogeneous coating of the MOF on the CNTs, and nanostructures of the CNT-MOF were controlled by simply changing the concentrations of the MOFs. Furthermore, this method was also applicable to graphene and graphene oxide (GO). Selective CO2 uptakes of the CNT-MOF and graphene-MOF were significantly improved as compared to the nonhomogeneous composites synthesized without the PVP functionalization, and a good reproducibility of the CO2 adsorption was confirmed by the cycling test
[Show abstract][Hide abstract] ABSTRACT: The rapidly approaching smart/wearable energy era necessitates advanced rechargeable power sources with reliable electrochemical properties and versatile form factors. Here, as a unique and promising energy storage system to address this issue, we demonstrate a new class of heterolayered, one-dimensional (1D) nanobuilding block mat (h-nanomat) battery based on unitized separator/electrode assembly (SEA) architecture. The unitized SEAs consist of wood cellulose nanofibril (CNF) separator membranes and metallic current collector-/polymeric binder-free electrodes comprising solely single-walled carbon nanotube (SWNT)-netted electrode active materials (LiFePO4 (cathode) and Li4Ti5O12 (anode) powders are chosen as model systems to explore the proof of concept for h-nanomat batteries). The nanoporous CNF separator plays a critical role in securing the tightly interlocked electrode-separator interface. The SWNTs in the SEAs exhibit multifunctional roles as electron conductive additives, binders, current collectors and also non-Faradaic active materials. This structural/physicochemical uniqueness of the SEAs allows significant improvements in the mass loading of electrode active materials, electron transport pathways, electrolyte accessibility and misalignment-proof of separator/electrode interface. As a result, the h-nanomat batteries, which are easily fabricated by stacking anode SEA and cathode SEA, provide unprecedented advances in the electrochemical performance, shape flexibility and safety tolerance far beyond those achievable with conventional battery technologies. We anticipate that the h-nanomat batteries will open 1D nanobuilding block-driven new architectural design/opportunity for development of next-generation energy storage systems.
[Show abstract][Hide abstract] ABSTRACT: The design and fabrication of oxygen barrier films is important for both fundamental and industrial applications. We prepared three different thin films composed of graphene oxide (GO) and laponite (LN), a typical low cost inorganic clay, with the GO/LN volume ratios of 1.9/0.1, 1.7/0.3 and 1.5/0.5 together with a double layer film of the GO and LN. We found that the films with GO/LN = 1.9/0.1 and the double layers exhibited high oxygen barrier and oxygen transmission rate values that reached 0.55 and 0.37 cm(3) per m(2) per atm per day, respectively, which were much lower than those of the films prepared from the pure GO, only LN and GO/LN = 1.7/0.3 and 1.5/0.5. This study is important for the design and fabrication of a film from GO-based all inorganic nanomaterials for applications in gas-barrier membranes.
[Show abstract][Hide abstract] ABSTRACT: A solid-state electrolyte with reliable electrochemical performance, mechanical robustness and safety features is strongly pursued to facilitate the progress of flexible batteries. Here, we demonstrate a shape-deformable and thermally stable plastic crystal composite polymer electrolyte (denoted as “PC-CPE”) as a new class of solid-state electrolyte to achieve this challenging goal. The PC-CPE is composed of UV (ultraviolet)-cured ethoxylated trimethylolpropane triacrylate (ETPTA) macromer/close-packed Al2O3 nanoparticles (acting as the mechanical framework) and succinonitrile-mediated plastic crystal electrolyte (serving as the ionic transport channel). This chemical/structural uniqueness of the PC-CPE brings remarkable improvement in mechanical flexibility and thermal stability, as compared to conventional carbonate-based liquid electrolytes that are fluidic and volatile. In addition, the PC-CPE precursor mixture (i.e., prior to UV irradiation) with well-adjusted rheological properties, via collaboration with a UV-assisted imprint lithography technique, produces the micropatterned PC-CPE with tunable dimensions. Notably, the cell incorporating the self-standing PC-CPE, which acts as a thermally stable electrolyte and also a separator membrane, maintains stable charge/discharge behavior even after exposure to thermal shock condition (=130 °C/0.5 h), while a control cell assembled with a carbonate-based liquid electrolyte and a polyethylene separator membrane loses electrochemical activity.
[Show abstract][Hide abstract] ABSTRACT: As a promising power source to boost up advent of next-generation ubiquitous era, high-energy density lithium-ion batteries with reliable electrochemical properties are urgently requested. Development of the advanced lithium ion-batteries, however, is staggering with thorny problems of performance deterioration and safety failures. This formidable challenge is highly concerned with electrochemical/thermal instability at electrode material-liquid electrolyte interface, in addition to structural/chemical deficiency of major cell components. Herein, as a new concept of surface engineering to address the abovementioned interfacial issue, multifunctional conformal nanoencapsulating layer based on semi-interpenetrating polymer network (semi-IPN) is presented. This unusual semi-IPN nanoencapsulating layer is composed of thermally-cured polyimide (PI) and polyvinyl pyrrolidone (PVP) bearing Lewis basic site. Owing to the combined effects of morphological uniqueness and chemical functionality (scavenging hydrofluoric acid that poses as a critical threat to trigger unwanted side reactions), the PI/PVP semi-IPN nanoencapsulated-cathode materials enable significant improvement in electrochemical performance and thermal stability of lithium-ion batteries.
[Show abstract][Hide abstract] ABSTRACT: We have reported the fabrication of flexible graphene-paper electrode (GPE) with a flat surface, whose internal structure has been formed with gradient porous build-up (from the surface to the 2-hydroxyethyl cellulose (HC)-coated paper). HC solution was used as a binder to form the gradient porous graphene layer, enabling it to create an anchoring force between the porous graphene layer and the filter paper. The morphology of GPE was investigated using a scanning electron microscope, and the surface resistance of the GPE as a function of graphene content was determined using four-probe method. The electrochemical performance of the GPE was evaluated using a three-electrode test cell by cyclic voltammetry. The gravimetric capacitance of GPE was found to be 120 F per gram of graphene, and the capacitance retention was within ca. 96% for over 500 cycles. This could be attributed to both the low surface resistance resulting from the flat surface and the high electrochemical activity caused by the gradient porous structure. This unique structure not only offers an enhanced conductivity and good electrical contact between the electrode and electrolyte but also helps GPE to maintain good cyclic stability, proving its potential for use in various rechargeable and portable energy-storage devices.
Journal of Nanoscience and Nanotechnology 11/2013; 13(11):7391-5. DOI:10.1166/jnn.2013.7860 · 1.56 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The electrospray-deposited patterns of graphene onto filter paper were characterized to study the effect of cellulose acetate phthalate (CAP) binder on the surface resistance of the resulting paper. The amount of CAP determines the extent of penetration of graphene into the heterogeneous networks, because graphene gets anchored and crowded into the network with CAP. A graphene-dispersed ink was prepared in water using sodium dodecylbenzenesulfonate, and this ink was used to fabricate graphene-coated paper (GCP) by electrospray deposition technique. The SEM images of the GCP revealed the impregnation of graphene into the filter paper. The mechanical properties and surface resistance of the GCP were studied using a universal testing machine (UTM) and indigenous four-probe meter, respectively. The low-cost GCP prepared in this study showed relatively low surface resistance (96.2 omega/sq) owing to the effective electro-conducting pathway provided by the crowded and impregnated deposition of grapheme onto the filter paper. Consequently, CAP improved the electrical and mechanical characteristics of GCP, even though only a small amount of graphene was used during deposition.
Journal of Nanoscience and Nanotechnology 10/2013; 13(10):7108-11. DOI:10.1166/jnn.2013.7873 · 1.56 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We demonstrate a bendable plastic crystal polymer electrolyte (referred to as “B-PCPE”) for use in flexible lithium-ion batteries. The B-PCPE proposed herein is composed of a plastic crystal electrolyte (PCE, 1 M lithium bis-trifluoromethanesulphonimide (LiTFSI) in succinonitrile (SN)) and a UV (ultraviolet)-cured polymer network bearing long linear hydrocarbon chains (here, trimethylolpropane propoxylate triacrylate (TPPTA) polymer is exploited). The solid electrolyte characteristics of the B-PCPE are investigated in terms of plastic crystal behavior, mechanical bendability, ionic conductivity, and cell performance. Owing to the presence of long linear hydrocarbon chains attached to crosslinkable acrylate groups, the TPPTA polymer network in the B-PCPE acts as a compliant mechanical framework, thereby exerting a beneficial influence on bendability and also interfacial resistance with lithium metal electrodes. Meanwhile, the B-PCPE exhibits slightly lower ionic conductivity than a control sample (referred to as “R-PCPE”) incorporating a rigid and stiff polymer network of ethoxylated trimethylolpropane triacrylate (ETPTA). This unique behavior of the B-PCPE is discussed with an in-depth consideration of the polymer network structure and its specific interaction with the lattice defect phase of SN in the PCE. Although relatively sluggish ionic transport is observed in the B-PCPE, its intimate interfacial contact with electrodes (possibly due to the mechanically compliant TPPTA polymer network) may beneficially contribute to imparting satisfactory cycling performance.
[Show abstract][Hide abstract] ABSTRACT: A facile approach to fabricate a highly bendable plastic crystal composite electrolyte (PCCE) for use in shape conformable all-solid-state lithium-ion batteries is demonstrated. This strategy is based on integration of a semi-interpenetrating polymer network (semi-IPN) matrix with a plastic crystal electrolyte (PCE, 1 M lithium bis-trifluoromethanesulfonimide in succinonitrile). In comparison to conventional carbonate-based electrolytes, salient benefits of the PCE are the thermal stability and nonflammability, which show promising potential as a safer electrolyte. The semi-IPN matrix in the PCCE is composed of a UV (ultraviolet)-crosslinked ethoxylated trimethylolpropane triacrylate polymer network and polyvinylidene fluoride-co-hexafluoropropylene (as a linear polymer). Solid electrolyte properties of the PCCE are investigated in terms of plastic crystal behavior, mechanical bendability, and ionic transport. Owing to the presence of the anomalous semi-IPN matrix, the PCCE exhibits unprecedented improvement in bendability, along with affording high ionic conductivity. Based on this understanding of the PCCE characteristics, feasibility of applying the PCCE to solid electrolytes for lithium-ion batteries is explored. The facile ionic transport of the PCCE, in conjunction with suppressed growth of cell impedance during cycling, plays a crucial role in providing excellence in cell performance. These advantageous features of the PCCE are further discussed with an in-depth consideration of the semi-IPN matrix architecture and its specific interaction with the PCE.
[Show abstract][Hide abstract] ABSTRACT: The deoxyribonucleic acid (DNA)-coated multi-walled carbon nanotube (MWNT) hybrid fibers were fabricated by wet-spinning method. The fibers were made up with entangled nanowire networks of DNA-coated MWNTs, and it shows a strain of ∼0.15% as electrochemical actuators under low potential cycling between 0 and −0.9 V versus Ag/AgCl in 2 M NaCl solution. The fibers also show good electric conductivity (∼60 S/cm) and capacitance (50 ± 5 F/g) behaviors. Based on the appropriation of its electro-chemo-mechanical systems, the DNA/MWNT fiber can be one of the new intelligent materials for biomedical application.
Sensors and Actuators B Chemical 02/2012; 162(1-1):173-177. DOI:10.1016/j.snb.2011.12.063 · 4.10 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Maleic Anhydride (MAH) was grafted onto poly(L-lactic acid) (PLLA) in the presence of dicumyl peroxide (DCP) as a radical initiator. The effect of the MAH and DCP concentrations on the grafting and the physical and mechanical properties of PLLA films were investigated. The glass transition temperature and crystallinity significantly decreased with addition of MAH. The thermal decomposition of the PLLA films was affected by the MAH content while the mechanical properties were almost unchanged. A slight increase in molecular weight was found, which could be attributed to either the MAH branching reaction or a possible crosslinking reaction between the PLLA chains increasing the chain entanglements.
[Show abstract][Hide abstract] ABSTRACT: The swelling behavior of chitosan hydrogels in ionic liquid–water binary systems was studied using hydrophilic room-temperature ionic liquids (RTILs) to elucidate the swelling properties of chitosan hydrogels. It was confirmed that chitosan hydrogels are much stiffer after immersing in a pure RTIL because the water existing inside the chitosan polymer network is extracted into the RTIL. The pH of the binary system changes when the RTIL is in contact with water. The chitosan hydrogels were fully dissociated at a 90% water content in the BMI-BF4-water binary system. The equilibrium binary system content behavior of the chitosan hydrogels depended upon the amount of free water present. The water behavior in a pure RTIL was examined using differential scanning calorimetry.
[Show abstract][Hide abstract] ABSTRACT: Composite fibers composed of chitosan and single-wall carbon nanotubes (CNTs) have been fabricated using a wet spinning method. The dispersion was improved by the sonic agitation of the CNTs in a chitosan solution followed by centrifugation to remove tube aggregates and any residual catalyst. The mechanical behavior was investigated using a dynamic mechanical analyzer (DMA). The mechanical tests showed a dramatic increase in Young's modulus for the chitosan/CNT composite fibers fabricated using the improved dispersion method. The strain on the microfibers was determined from tensile load measurements during pH switching in acidic or basic electrolyte solutions. The microfibers showed a general actuation behavior of expanding at pH = 2 and contracting at pH = 7 under low tensile loads. However, a reverse of this actuation behavior was exhibited under high tensile loads. This anomalous pH actuation is both new and surprising. It was explained from an analysis of the differences in sample stiffness and Poisson’s ratio under tensile load in electrolyte solutions with different pH values.
[Show abstract][Hide abstract] ABSTRACT: A high-surface-area material has recently attracted interest in actuator systems. We report on improved performance of the simultaneous electrochemical linear actuation of conducting polymer (CP)/carbon nanotube (CNT) hybrid fibers using porous structured deoxyribonucleic acid (DNA) hydrogels. It was deduced that individual DNA-wrapped CNTs had efficiently doped the PPy on its inner and outer surface through the association of PPy with the DNA via a supramolecular interaction. To assess the potential of the PPy/DNA/CNT hybrid fibers for use in electrochemical capacitors and actuators, we showed that the redox response of the hybrid fibers was improved by the addition of DNA to the PPy/CNT film. The values of the measured electrochemical capacitance (∼371 F/g in a lithium bis(trifluoromethylsulfonyl)imide aqueous solution, where the joint mass of PPy, DNA, and CNT was considered) were higher than those of previous CNT/PPy composite films with a controlled pore size (∼250 F/g). The fibers showed actuation stability with an expansion and contraction of ∼4.41% under a low potential (±1 V). DNA/PPy/CNT hybrid fibers will form the basis for new intelligent materials for applications such as bio-artificial muscles.
Sensors and Actuators B Chemical 03/2010; 145(1-145):89-92. DOI:10.1016/j.snb.2009.11.043 · 4.10 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Tough and soft: Highly porous, spongelike materials self-assemble by calcium ion condensation of DNA-wrapped carbon nanotubes (SWNTs-DNA; see picture, IL = ionic liquid). The toughness, modulus, and swellability of the electrically conductive sponges can be tuned by controlling the density and strength of interfiber junctions. The sponges have compliances similar to the softest natural tissue, while robust interfiber junctions give high toughness.