Supercapacitors fabricated from fiber materials are becoming important electrochemical energy storage devices owing to their high flexibility, light weight and high energy density. They are used in electronic systems such as information sensing, computation, communication and electronic textiles due to their higher power density than standard parallel plate capacitors and batteries. Here, the effects of the composition, spinning and fabrication conditions on the electrochemical performance of supercapacitors fibers made from carbon nanotubes, graphene and poly(3,4- ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) are reviewed in the context of wearable energy storage devices.
摘要: Sodium-ion batteries (SIBs) have received extensive research interest as an important alternative to lithium-ion batteries in the electrochemical energy storage field by virtue of the abundant reserves and low-cost of sodium. In the past few years, carbon and its composite materials used as anode materials have shown excellent sodium storage properties through structural design and composition regulation. The increasing popularity of wearable electronics has demanded higher requirements for electrode materials. A free-standing electrode is able to eliminate the massive use of electrochemical inactive binders and conductive additives, thereby increasing the overall energy density of the battery system. Research progress on carbon materials such as carbon nanofibers, carbon nanotubes and graphene and their composites (metallic compounds and alloy-type materials) is summarized. The preparation strategies and electrochemical properties of free-standing carbon-based anodes with and without substrates are categorized and reviewed. Finally, proposals are made for future research and developments for free-standing carbon-based anodes for SIBs.
One of the most important research areas related to Li-ion batteries is the replacement of the graphite anode with other carbon materials such as hard carbons, activated carbons, carbon nanotubes, graphene, porous carbons, and carbon fibers. Although such materials have shown better electrochemical performance for lithium storage compared to graphite, there is plenty of room for improvement. One of the most effective approaches is to dope heteroatoms (e. g. nitrogen) in the structure of the carbon materials to improve their electrochemical performance when they are used as anode materials. We first describe how N-doping has a positive effect on lithium storage and then provide numerous selected examples of this approach being applied to various carbon materials. The characterization of N doped in the structure of different carbon materials by X-ray photoelectron spectroscopy and scanning tunneling microscopy is then presented since they are able to characterize the N in these structures with a high (atomic) resolution. Finally, a statistical analysis is performed to show how the amount of doped N affects the specific capacity of the N-doped carbon materials.
摘要: Reducing CO2 emission has become one of the most urgent issues in the world. The use of abundant solar energy to convert carbon dioxide into carbon-based chemicals would be a tremendous advance. There are many papers on photocatalysis or thermal catalysis in the reduction of CO2, however, there is little research on photothermal catalysis for this purpose. We summarize our current knowledge of this topic, and the classification of catalysts (new carbon materials, oxide materials, metal sulfide materials, MOF materials, layered double hydroxide materials), their modification and their use in the reduction of CO2 is discussed. Trends in the development of new catalysts are considered.
摘要: 较低的体积能量密度限制了当前电化学电容器的应用，而提高体积能量密度的关键在于发展具有致密化储能特性的多孔炭材料。目前，毛细致密化已成为平衡多孔炭密度和孔隙率从而提高材料体积比电容的主要方法，但仍在孔结构的精细调控方面存在不足，制约了毛细致密化多孔炭与高电压离子液体的兼容性。本文提出了碘化钾（KI）辅助的毛细致密化策略，通过在石墨烯网络中预载KI来控制毛细致密化过程，实现了对孔结构的有效调控。同时电化学性能表征结果表明KI具有增加离子到达表面积和提供赝电容的作用。基于此，所制碘化钾/石墨烯材料的密度达到0.96 g cm−3，在离子液体中的体积比电容为115 F cm−3。由该材料所组装的电化学电容器可以提供19.6 Wh L−1的体积能量密度。
摘要: Graphite is one of the most promising anode materials for potassium-ion batteries (PIBs) due to its low cost and stable discharge plateau. However, its poor rate performance still needs to be improved. A novel graphitic anode was designed from commercial mesocarbon microbeads (MCMBs) by KOH treatment. Using limited oxidation and slight intercalation, the interlayer spacing of graphitic layers on the surface of the MCMBs was increased, causing the K+ diffusion rate to be significantly improved. When this modified material was combined with carboxymethyl cellulose as a binder (79.2%) and used as a PIB anode, it had a high plateau capacity below 0.25 V (271 mAh g−1), superior rate capability (160 mAh g−1 at 1.0 A g−1), excellent cycling stability (about 184 mAh g−1 after 100 cycles at 0.1 A g−1), and a high initial coulombic efficiency. This work provides a simple strategy to prepare graphitic materials with an excellent potassium storage performance.
摘要: In lithium-sulfur (Li-S) batteries, the electrochemical properties of the sulfur cathode are determined by the sulfur host, and this controls the shuttle effect and the kinetics, two of the major problems in these batteries. We confined the S in hollow thin-wall C/Mo2C particles smaller than 7 nm across that clustered together to form micrometer-size particles. The conducting network of C/Mo2C shells facilitates lithium-ion and electron transport while acting as a barrier to the outward diffusion of polysulfides. They also improve the redox kinetics because of the catalytic conversion of polysulfides to sulfur. As a result of these features the material achieved a high reversible capacity of 1210 mAh g−1 at 0.5 C with a low capacity fade rate of 0.127% per cycle over 300 cycles and a high rate performance (780 mAh g−1 at 3.0 C). It is expected that this work will help in the design of sulfur hosts for Li-S batteries with a high rate performance and high cycling stability.
摘要: 碳点（CDs）是一种新兴的碳纳米材料，因其高比表面积、良好的分散性、丰富的表面官能团、低生物毒性和光致发光特性而受到了研究者的广泛关注。然而，低成本、大规模和绿色合成CDs仍面临挑战。本工作基于生物质玉米芯特殊的天然孔隙结构，经直接炭化制备具有定向、贯通微纳米孔道的多孔三维电极材料，在毛细作用下电解液可以充满整个电极材料，内外表面同时发生电化学氧化，实现高效制备CDs。在1 A恒电流下，每克电极材料制备CDs速率达到了79.83 mg h−1。将制备的CDs与氧化石墨烯（GO）水热复合得到复合气凝胶CDs/rGO材料，经热处理后应用于钠离子电池。在1 A g−1下循环1000圈仍保持263.3 mAh g−1的容量。本研究工作采用生物质玉米芯高效制备CDs，为CDs的大规模绿色制备和应用提供了新的途径和思路。
摘要: A graphene-(Ni-NiO)-C hybrid was prepared by dissolving nickel acetate and glucose in water to form a solution that was mixed with a graphene oxide (GO) aqueous suspension, hydrothermally treated at 180 °C for 24 h, carbonized at 700 °C for 3 h in Ar and calcined at 300 °C for 3 h in air. Results indicated that Ni(OH)2 formed during the hydrothermal treatment was converted to metallic Ni during carbonization, which was partly oxidized to NiO during calcination. When used as the anode material of a lithium-ion battery, it had a high initial capacity of 711.6 mA h g−1, which increased to 772.1 mA h g−1 after 300 cycles. For comparison, the sample without added GO had a much lower initial capacity of 584.7 mA h g−1, which decreased to 148.8 mA h g−1 after 300 cycles. Hybridization of the Ni-NiO nanoparticles with carbon inhibited their aggregation. The GO addition led to the formation of a conducting network, which alleviated the large volume expansion during lithiation, prevented the electrode from cracking during cycling and increased the surface area for easy access of the electrolyte. These factors jointly contributed to the obvious improvement in the electrochemical performance of the graphene-(Ni-NiO)-C anode.
摘要: Mesophase pitch-based carbon fibers (MPCFs) have a high modulus of elasticity, low electrical resistivity and high thermal conductivity, so can be used in many fields. Carbon fibers were prepared from two naphthalene-based mesophase pitches, one synthesized by a HF/BF3 catalytic one-step method (AR-MP) and the other by an AlCl3 catalytic two-step method (N-MP). The mesophase pitches, spun pitch fibers, pre-oxidized fibers, carbonized fibers and graphitized fibers produced from them were characterized by TG-MS, FT-IR, 13C-NMR, MALDI-TOF-MS, XRD, SEM and elemental analysis. The molecular structures and properties of mesophase pitches were compared, and the effects of molecular structures on the structures and properties of the carbon fibers produced from them were measured. In comparison to N-MP, AR-MP has a rod-like semi-rigid molecular configuration containing more naphthenic structures and methyl side chains. The pre-oxidized fibers derived from AR-MP have a better carbon layer orientation, so that their graphitized fibers have a higher thermal conductivity of 716 W/(m·K). N-MP has a higher aromaticity with a disc-like rigid molecular configuration, so that the graphitized fibers prepared from it have a higher tensile strength of 3.47 GPa due to fewer defects being formed during preparation. The molecular structures of AR-MP and N-MP have an obvious influence on the structures and properties of their graphitized fibers.
摘要: A novel pantograph carbon slider (PCS-1) was designed and prepared via mold pressing, hot extrusion and sintering using sulfonated graphene (SG) as additive. The results show that PCS-1 demonstrates an obvious enhanced mechanical strength and wear performances than that of carbon slider in the absence of SG (PCS-0). For example, the current-carrying wear test indicates that the flexural strength of PCS-1 is 41.8% higher than that PCS-0 counterparts. The wear rate of PCS-1 reduces 51.0% and 50.0% in the wet and normal conditions, respectively. Moreover, the presence of SG, as reflected in scanning electron microscopy, polarizing microscope and white light interferometer, can markedly decrease the number of random cracks, increase the compactness of fracture surface and inhibit the electro-erosion of the slider materials, thus improving the mechanical strength and wear resistance significantly.
摘要: An anodized carbon fiber tow was continuously sized using aqueous polyurethane to improve the interfacial properties of carbon fiber-reinforced polyurethane composites. These were investigated by interlaminar shear strength (ILSS) tests, elemental and functional group analysis, thermal gravimetric analysis, and differential scanning calorimetry. Results show that the polyurethane sizing agent significantly improves the interfacial properties of the composites. The ILSS of the sized carbon fiber-reinforced composite is increased by 17.5% (from 39.5 to 46.4 MPa) compared to that of the oxidized carbon fiber-reinforced counterpart. Treating the sized carbon fiber-reinforced composite at 170 °C further increased the ILSS by 9.5% to 50.8 MPa. It is considered that the sizing agent interacts with oxygen-containing functional groups on the oxidized carbon fiber surface to form hydrogen bonds with the resin matrix. Upon heating at 170 °C, blocking groups in the sizing agent are unblocked to expose the isocyanate roots that react with the carbamate of the matrix to generate allophanate. It is concluded that a polyurethane sizing agent is suitable for improving the interfacial properties of carbon fiber-reinforced polyurethane resin composites, and that heating after curing further improves these properties.
摘要: The microstructure of nuclear graphite, a key material in nuclear reactors, is affected by the high-flux irradiation. The damage to the graphite by irradiation is important for reactor safety. To understand the damage of nuclear graphite by irradiation, IG-110 nuclear graphite, a representative nuclear graphite, was chosen to investigate the change in morphology and microstructure caused by 7 MeV Xe26+ irradiation with peak damage doses of 0.1-5.0 displacements per atom (dpa) for samples of a size of 40.0 mm×40.0 mm×2.0 mm. The topography and microstructure of IG-110 were characterized by SEM, AFM, grazing incidence XRD, Raman spectroscopy and nano-indentation. Results indicate that after 7 MeV Xe26+ irradiation at a dose of 0. 11 dpa, a ridge-like structure appears on the surface of the IG-110 graphite, mainly in the binder region, and the surface roughness increases slightly. With a further increase of the irradiation dose, the ridge-like structure also appears in the filler region. At a dose of 0.55 dpa, pore shrinkage increases accompanied by pore closure, and the surface roughness also increases. The changes in topography and microstructure caused by irradiation are attributed to the expansion of graphite along the c-axis direction. With increasing irradiation dose the defect density and the degree of in-plane disorder in the graphene sheets increases, while the modulus and hardness of the graphite first increase and then decrease. Their increase is caused by dislocation pinning and closure of fine pores, while their decrease is attributed to an increase in porosity and the generation of an amorphous structure.
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