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Sodium‐ion capacitors (SICs), designed to attain high energy density, rapid energy delivery, and long lifespan, have attracted much attention because of their comparable performance to lithium‐ion capacitors (LICs), alongside abundant sodium resources. Conventional SIC design is based on battery‐like anodes and capacitive cathodes, in which the battery‐like anode materials involve various reactions, such as insertion, alloying, and conversion reactions, and the capacitive cathode materials usually depend on activated carbon (AC). However, researchers have attempted to construct SICs based on battery‐like cathodes and capacitive anodes or a combination of both in recent years. In this Minireview, charge storage mechanisms and material design strategies for SICs are summarized, with a focus on the battery‐like anode materials from both inorganic and organic sources. Additionally, the challenges in the fabrication of SICs and future research directions are discussed. [ABSTRACT FROM AUTHOR]

Abstract: Mesoporous carbon can be synthesized with good control of surface area, pore‐size distribution, and porous architecture. Although the relationship between porosity and supercapacitor performance is well known, there are no thorough reports that compare the performance of numerous types of carbon samples side by side. In this manuscript, we describe the performance of 13 porous carbon samples in supercapacitor devices. We suggest that there is a “critical pore size” at which guest molecules can pass through the pores effectively. In this context, the specific surface area (SSA) and pore‐size distribution (PSD) are used to show the point at which the pore size crosses the threshold of critical size. These measurements provide a guide for the development of new kinds of carbon materials for supercapacitor devices. [ABSTRACT FROM AUTHOR]

Lithium-sulfur (Li−S) batteries are one of the most promising candidates for the next generation of energy-storage devices owing to their high theoretical energy and low cost. However, low practical energy density and poor cycling life are obstacles to the practical application of Li−S batteries. A highly conductive and lightweight poly(3,4-ethylenedioxythiophene):polystyrene sulfonate-carbon nanotube (PEDOT:PSS-CNT) interlayer for Li−S batteries has been fabricated. The PEDOT:PSS-CNT interlayer not only acts as a soft buffer to scavenge excess lithium polysulfides in the pores and restricts polysulfides from migrating to the lithium anode by chemical absorption, but also serves as an assisted 'current collector' to improve the electronic conductivity for the sulfur cathode. With these synergistic contributions, pure sulfur cathode with the PEDOT:PSS-CNT interlayer shows a high capacity (921 mA h g−1at 0.5 C; 1 C=1675 mA h g−1), enhanced cycling performance (a capacity retention of 70.9 % after 200 cycles), and good rate performance. The excellent electrochemical performance of the sulfur cathode plus the easy fabrication of such a functional interlayer bring feasible Li−S batteries for practical applications one step closer. [ABSTRACT FROM AUTHOR]

An efficient anion-exchange protocol was investigated for the controllable fabrication of hollow NiCo2S4 nanoboxes (NBs) from mesocrystalline nickel cobalt carbonate nanocubes as promising pseudocapacitive materials for electrochemical capacitors. The underlying processes of the formation of the hollow architecture were systematically investigated. Originating from the unique structural and compositional advantages, the resultant hollow NiCo2S4 NB electrode with a loading of 5 mg cm2 delivered a large specific capacitance of 777 F g−1 at a high rate of 4 A g−1 in a three-electrode configuration with 6 m KOH as electrolyte. Furthermore, an asymmetric device constructed with the hollow NBs and activated carbon (AC) as positive and negative electrodes, respectively, showed extraordinary supercapacitance within an electrochemically operating voltage window from 0.0 to 1.5 V. The unique AC//NiCo2S4 NB hybrid capacitor exhibited a large specific energy density (active mass normalized) of approximately 17.1 W h kg−1 at a high power density of 2250 W kg−1, and desirable cycling durability with approximately 75 % specific capacitance retention after 5000 consecutive cycles at a current rate of 2 A g−1. These electrochemical investigations strongly indicated that the as-fabricated hollow NiCo2S4 NBs can be elegantly utilized as powerful candidates for advanced electrode platforms. [ABSTRACT FROM AUTHOR]

Metal-organic framework (MOF)-derived carbon materials exhibit large surface areas, but dominant micropore characteristics and uncontrollable dimensions. Herein, we propose a self-sacrificial template-directed synthesis method to engineer the porous structure and dimensions of MOF-derived carbon materials. A porous zinc oxide (ZnO) nanosheet solid is selected as the self-sacrificial template and two-dimensional (2D) nanostructure-directing agent to prepare 2D ZIF-8-derived carbon nanosheets (ZCNs). The as-prepared ZCN materials exhibit a large surface area with hierarchical porosity. These intriguing features render ZCN materials advanced electrode materials for electrochemical energy-storage devices, demonstrating large ion-accessible surface area and high ion-/electron-transport rates. This self-sacrificial template-directed synthesis method offers new avenues for rational engineering of the porous structure and dimensions of MOF-derived porous carbon materials, thus exploiting their full potential for electrochemical energy-storage devices. [ABSTRACT FROM AUTHOR]

Porous carbon with high specific surface area (SSA), a reasonable pore size distribution, and modified surface chemistry is highly desirable for application in energy storage devices. Herein, we report the synthesis of nitrogen-containing mesoporous carbon with high SSA (1390 m2 g−1), a suitable pore size distribution (1.5-8.1 nm), and a nitrogen content of 4.7 wt % through a facile one-step self-assembly process. Owing to its unique physical characteristics and nitrogen doping, this material demonstrates great promise for application in both supercapacitors and encapsulating sulfur as a superior cathode material for lithium-sulfur batteries. When deployed as a supercapacitor electrode, it exhibited a high specific capacitance of 238.4 F g−1 at 1 A g−1 and an excellent rate capability (180 F g−1, 10 A g−1). Furthermore, when an NMC/S electrode was evaluated as the cathode material for lithium-sulfur batteries, it showed a high initial discharge capacity of 1143.6 mA h g−1 at 837.5 mA g−1 and an extraordinary cycling stability with 70.3 % capacity retention after 100 cycles. [ABSTRACT FROM AUTHOR]

In this work, ternary metal nitrides are proposed as novel electrode materials for supercapacitors. We selectively fabricate ternary vanadium titanium nitride/carbon (VTiN/C) nanofibers through a facile electrospinning strategy and investigate their electrochemical performance for the first time. The obtained well-interconnected VTiN/C nanofibers with VTiN nanoparticles embedded into carbon ensure rapid electron/ion transfer and offer a highly ion-accessible surface. Appealingly, the VTiN-4/C nanofibers exhibit a greatly improved performance, with a high specific capacitance (430.7 F g−1, 0.5 A g−1) and a good rate capability. Furthermore, the performance of the VTiN/C nanofibers is found to be controllable by adjusting the V/Ti atomic ratio. The encouraging electrochemical performance suggests that ternary VTiN could be a promising electrode material for supercapacitors. [ABSTRACT FROM AUTHOR]

Sodium-ion batteries with good electrochemical performance are of great significance for grid-scale energy storage applications. Herein, an aqueous rechargeable Na-ion battery has been fabricated with multiwalled carbon nanotube (MWNT)-containing NaTi2(PO4)3/MWNTs nanocomposites as the anode and Na0.44MnO2 nanorods as the cathode in a 1 M aqueous Na2SO4 electrolyte and the device was carefully studied. Owing to the open framework structures (containing large interstitial sites) that both NaTi2(PO4)3 and Na0.44MnO2 possess, the fast Na-ions will facilitate free transport. Benefiting from their unique structural features, the aqueous battery system exhibited an average charge and discharge voltage of approximately 1.1 V, a high energy density of 58.7 Wh kg−1 in terms of total electroactive materials, and could deliver a reversible capacity of approximately 50 mAh g−1 after 300 cycles at 2 C rate; the corresponding coulombic efficiency was nearly constant at approximately 95 %. These results, together with the safety and cost perspectives of aqueous electrolytes indicated that the aqueous Na-ion battery may be a good candidate for safe, inexpensive, high-power energy storage systems. [ABSTRACT FROM AUTHOR]

A facile solution-based synthesis and characterization of a nitrogen-doped, carbon-coated Li4Ti5O12 (NC-LTO) nanocomposite is reported. The mesoporous TiO2 nanoparticles (NP--TiO2) are first prepared by using nanocrystalline cellulose (NCC) as a template and subsequently transform in situ into an NC-LTO nanocomposite with a core-shell structure by using the ionic liquid 1-ethyl-3-methylimdazolium tricyanomethanide as the carbon source. Various state-of-the-art techniques, including fieldemission SEM, TEM, scanning transmission electron microscopy, XRD, X-ray photoelectron spectroscopy, and thermogravimetric analysis, were performed to characterize the morphologies, structures, and compositions. Such NC-LTO nanocomposites have a well-defined LTO core and thin uniform carbon shell with a thickness of 1-2 nm. Electrochemical tests reveal that the NC-LTO nanocomposite delivers a reversible capacity of 171.5 mAhg--1 at 0.2 C, and shows remarkable rate capability by maintaining 63% of the capacity at 60 C (vs. 0.2 C), as well as excellent cycling stability with a capacity retention of 95% after 300 cycles at a rate of 10 C. The excellent electrochemical performance is attributed exclusively to the well-defined coreshell nanostructure and high electric conductivity. The nanosized LTO core can significantly shorten the transport lengths of lithium ions and the admirable electric conductivity of the nitrogen-doped carbon shell can act as an "expressway" for electrons and lithium ions to transport them between the anode material core and the electrolytes. [ABSTRACT FROM AUTHOR]

In this study, porous polypyrrole (PPy) film was synthesized by facile interfacial polymerization using ionic liquid as oxidant. The morphology of PPys changed from dense microspherical/nanospherical agglomerated structure to porous structure with the increasing concentration of the oxidant. The magnetic ionic liquid, 1-butyl-3-methylimidazolium tetrachloroferrate (Bmim[FeCl4]), played a major role of oxidant when the concentration was lower than 0.075 M. As the concentration increased to 0.075 M, the π-π interactions between pyrrole cations and iminazole ring of Bmim[FeCl4], as evidenced by Fourier transform infrared spectrometer results, may affect the packing of PPy chains and subsequently cause the formation of porous structure of PPys. Electrochemical performances showed that PPy with porous structure displayed the highest specific capacitance of 170 F/g at a current density of 2 A/g in 1 M H2SO4 solution and a good capacitive behavior, which has potential application as supercapacitor materials. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

A three-dimensional (3D) hierarchical carbon-sulfur nanocomposite that is useful as a high-performance cathode for rechargeable lithium-sulfur batteries is reported. The 3D hierarchically ordered porous carbon (HOPC) with mesoporous walls and interconnected macropores was prepared by in situ self-assembly of colloidal polymer and silica spheres with sucrose as the carbon source. The obtained porous carbon possesses a large specific surface area and pore volume with narrow mesopore size distribution, and acts as a host and conducting framework to contain highly dispersed elemental sulfur. Electrochemical tests reveal that the HOPC/S nanocomposite with well-defined nanostructure delivers a high initial specific capacity up to 1193 mAh g−1 and a stable capacity of 884 mAh g−1 after 50 cycles at 0.1 C. In addition, the HOPC/S nanocomposite exhibits high reversible capacity at high rates. The excellent electrochemical performance is attributed exclusively to the beneficial integration of the mesopores for the electrochemical reaction and macropores for ion transport. The mesoporous walls of the HOPC act as solvent-restricted reactors for the redox reaction of sulfur and aid in suppressing the diffusion of polysulfide species into the electrolyte. The 'open' ordered interconnected macropores and windows facilitate transportation of electrolyte and solvated lithium ions during the charge/discharge process. These results show that nanostructured carbon with hierarchical pore distribution could be a promising scaffold for encapsulating sulfur to approach high specific capacity and energy density with long cycling performance. [ABSTRACT FROM AUTHOR]

MnO2 nanosheets have been synthesized by using a redox reaction of manganese nitrate tetrahydrate and potassium permanganate without any surfactants. The morphology and microstructure of the as-prepared material were characterized by field emission scanning electron microscopy, transmission electron microscopy and X-ray diffraction (XRD). Electrochemical performances as electrode materials for supercapacitor were evaluated using cyclic voltammetry and galvanostatic charge-discharge in 1 M Na2SO4 aqueous electrolyte. It was found that MnO2 nanosheets showed an excellent capacitive behaviour with good cycling stability. The specific capacitance of the MnO2 nanosheet electrode can reach up to 332.8 Fg−1 at a current density of 500 mA/g and a stable cycling performance. [ABSTRACT FROM AUTHOR]

The cost-effective activated carbons derived from waste Camellia oleifera shell (COS) by ZnCl activation method are investigated as the active electrode material in electric double-layer capacitors (EDLCs) for the first time. The activation temperature and ZnCl/COS impregnation ratio are two key factors affecting the surface area and pore structure of the prepared activated carbons, which accordingly affect their capacitive performances. Electrochemical investigations indicate that the activated carbon (AC-3-600) obtained at the activation temperature of 600 °C and impregnation ratio of 3 shows the maximum specific capacitance of 374 and 266 F g in 1 mol L HSO and 6 mol L KOH electrolytes at 0.2 A g, respectively. The high capacitance of the AC-3-600 is attributed to its high surface area (1,935 m g), high total pore volume (1.02 cm g), and especially the large percentage of micropores (735 m g). Meanwhile, the activated carbon presents good cycle stability in both acid and alkaline electrolytes during 5,000 cycles at a fair current density of 4 A g. So, we had reasons to believe that the activated carbons from waste COS by ZnCl activation might be one of the innovative carbon electrode materials for EDLCs application. [ABSTRACT FROM AUTHOR]

A new simple, time-saving method of preparing highly dispersed Pt nanoparticles with large electrochemically active area (ECA) on three-dimensional dendrite-like Au supported on Si (100) was successfully developed by electroless displacement deposition (EDD). The as-prepared catalysts were characterized by field-emission scanning electron microscope and high-resolution transmission electron microscopy. The electro-catalytic properties of Pt/Au/Si for methanol and CO electrooxidation were investigated by cyclic voltammetry, chronoamperometry, and electrochemical impedances spectra. The results show that Pt/Au/Si catalyst prepared by EDD method presents the higher electro-catalytic activity and higher stability than that of Pt/Si composite. The electro-catalytic activity of Pt supported on Au could be enhanced with the growth of Au, leading to the higher electro-catalytic properties toward methanol and CO oxidation. The anodic peak of CO of Pt/Au/Si catalyst showed negatively shifted with respect to similarly prepared Pt/Si electrode. The supposed schematic of the reaction was also introduced. Overall, the approach provides a convenient method to prepare the Pt catalyst on Au dendrites with high ECA properties for DMFC and PEMFC through bottom-up assembly. [ABSTRACT FROM AUTHOR]

Abstract: A simple hydrothermal treatment was developed to synthesize Co3O4 powders with different morphologies in mass production by using hexamethylenetetramine (HMT, C6H12N4) as a precipitator. By changing the initial HMT concentrations, the prepared Co3O4 powders were readily regulated in its morphologies, which varied from microsphere to urchin-like hollow microsphere, and finally to collapsed porous structure. Moreover, the four Co3O4 powders with different HMT concentrations had been applied in the negative electrode materials for lithium ion batteries, which exhibited different electrochemical properties. The present research demonstrated that morphology was one of the crucial factors that affected the electrochemical properties of electrodes. The capacity retention of sample with an original Co(NO3)2:HMT mole ratio of 1:1 is almost above 94% from the 5th cycle at different current densities of 40 and 60mAg−1, exhibiting the better long-life stability and favorable electrochemical behaviors due to its higher specific surface area (97.1m2 g−1) and the uniform urchin-like hollow structure. [Copyright &y& Elsevier]

In this work, various novel NiO hierarchical nanostructures, including mesoporous nanotubes by nanoparticles self-assembly, nanowire bundles, dandelions, hollow spheres by rods self–assembly, have been fabricated by a simple hydrothermal process and subsequent thermal decomposition at atmosphere. A detailed study of the effect of experimental parameters on the morphology is also presented. Results and analyses demonstrated that oxalic-acid/NaOH molar ratio has an immense function in the subtle morphology control of NiO products. Electrochemical characterization demonstrated that the mesoporous NiO nanotubes were capable of delivering a specific capacitance (SC) of 405 F g−1at the current density of 0.5 A g−1and offered good capacitance retention of ca.91% after 1500 continuous charge-discharge cycles. This soundly indicates that as electrode material, the as-prepared NiO mesoporous nanostructures could meet key requirements in terms of large power density, outstanding rate capability and excellent electrochemical stability. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) materials have attracted significant research interests for energy-storage applications owing to their unique structural and electronic properties. The modification of 2D materials with ordered mesoporous carbon (OMC) offers great opportunities for increasing the ion-accessible surface area and improving the ion diffusion. Herein, we report an unprecedented type of heterostructured MXene (Ti 3 C 2 T x)/nitrogen-doped OMC (NOMC) hybrid, which is prepared via the self-assembly of melamine resol-P123 micelles with exfoliated Ti 3 C 2 T x nanosheets. The NOMC exhibits well-ordered mesopores which are aligned with Ti 3 C 2 T x nanosheet surface. This novel structure not only prevents the stacking of MXene nanosheets, but also provides a fast ion-diffusion path. When used as an electrode material for supercapacitors, the Ti 3 C 2 T x -NOMC hybrid exhibits a high gravimetric capacitance of 329 F g−1 and a volumetric capacitance of 823 F cm−3. Furthermore, the Ti 3 C 2 T x -NOMC composite also displays excellent rate capability and good cycling stability, thus highlighting the benefit of hybridizing MXene with ordered mesoporous carbon for for enhancing the energy storage performance. An unprecedented type of heterostructured MXene (Ti 3 C 2 T x)/nitrogen-doped OMC (NOMC) hybrid material is prepared via the self-assembly of phenol-melamine-formaldehyde resol-P123 micelles with exfoliated Ti 3 C 2 T x nanosheets followed by carbonization. Image 1 • Heterostructured Ti 3 C 2 T x /N-doped OMC (NOMC) hybrid is prepared via self-assembly of resol-P123 micelles with exfoliated Ti 3 C 2 T x nanosheets. • The NOMC layers can not only prevent the restacking of Ti 3 C 2 T x layers, but also provide fast ion-diffusion paths. • The Ti 3 C 2 T x -NOMC hybrid exhibits both high gravimetric and volumetric performance as electrode material for supercapacitors. [ABSTRACT FROM AUTHOR]

A flexible graphene (GN)-based film has been prepared by flow-directed assembly from a complex dispersion of GN and mesoporous carbon nanosphere (MCS) functionalized with poly dimethyl diallyl ammonium chloride. Morphology analysis displays that the presence of MCS has effectively prevent the restacking of individual GN sheets, favoring electrolyte ions easier access to the surfaces of GNs in forming electric double-layers. In application as a supercapacitor in 1 M KOH electrolyte, GN/MCS film shows superior electrochemical performance, including high specific capacitance (211 F g −1 at 0.2 A g −1 ), good rate capability (61% capacity retention at 20 A g −1 ) and excellent electrochemical stability (4% capacity loss after 5000 cycles). [ABSTRACT FROM AUTHOR]

Abstract: Graphite oxide/polypyrrole composites (GPys) were prepared by in situ polymerization and reduced by NaBH4 to prepare reduced graphite oxide/polypyrrole composites (R-GPys). On the basis of the morphological and structural characterization of the composites by Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD) and transmission electron microscopy (TEM) tests, the electrochemical performances of the composites were investigated by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance techniques. The experimental results showed that the specific capacitances of the composites before and after reduction (197 and 180F/g) were highly improved compared with that of pristine graphite oxide (11F/g) and polypyrrole (112F/g), respectively. The capacitance retention of about 73% for R-GPys compared with 12% for PPy and 47% for GPys after 1200 cycles indicated the high cycle stability of the R-GPys and its potential as an electrode material for supercapacitor applications. [Copyright &y& Elsevier]

Abstract: One-dimensional nanostructured manganese dioxide/polypyrrole (MnO2/PPy) composite was prepared by in situ chemical oxidation polymerization of pyrrole in the host of inorganic matrix of MnO2, using complex of methyl orange (MO)/FeCl3 as a reactive self-degraded soft-template. The morphology and structure of the composite were characterized by infrared spectroscopy (IR) X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that the MnO2/PPy composite consists of α-MnO2 and PPy with nanotube-like structure. Electrochemical properties of the composite demonstrated the material showed good electrochemical reversibility after 500 charge–discharge cycles in the potential range of −0.4 to 0.6V, the tube-like nanocomposite has the potential application in electrochemical capacitor. [Copyright &y& Elsevier]

Highlights: [•] PEDOT/graphene composite hydrogel was prepared by in situ polymerization. [•] The 3D porous structure of hydrogel is controlled by supramolecular self-assembly. [•] Introduction of graphene caused the improved conductivity and specific capacitance. [•] A high capacitance value of 220F/g was obtained at a high current density of 5A/g. [Copyright &y& Elsevier]

Abstract: In this study, polypyrrole (PPy)/multi-walled carbon nanotubes (MWCNTs) nanocomposites (PCNs) with core–shell structure were synthesized by a novel ternary phase interfacial polymerization. The thickness of the PPy shell can be tuned by changing the mass feeding ratio of MWCNTs to pyrrole. Increasing the pyrrole content from 50 to 90wt%, the thickness of the PPy layer increased from about 30nm to 80nm. The probable formation mechanism for the core–shell structure of the nanocomposites was proposed. The utilizations of both ternary system and 1-butyl-3-methylimidazolium tetrachloroferrate (Bmim[FeCl4]) for the interfacial polymerization favored the self assembly of PPy on the surface of MWCNTs. Electrochemical performances show that PCNs with pyrrole content of 90wt% obtained high specific capacitance as well as ideal capacitive behavior. [Copyright &y& Elsevier]

Abstract: The flexible electrodes have important potential applications in energy storage of portable electronic devices for their powerful structural properties. In this work, unique flexible films with polypyrrole/carbon nanotube (PPy/CNT) composite homogeneously distributed between graphene (GN) sheets are successfully prepared by flow-assembly of the mixture dispersion of GN and PPy/CNT. In such layered structure, the coaxial PPy/CNT nanocables can not only enlarge the space between GN sheets but also provide pseudo-capacitance to enhance the total capacitance of electrodes. According to the galvanostatic charge/discharge analysis, the mass and volume specific capacitances of GN-PPy/CNT (52wt% PPy/CNT) are 211Fg−1 and 122Fcm−3 at a current density of 0.2Ag−1, higher than those of the GN film (73Fg−1 and 79Fcm−3) and PPy/CNT (164Fg−1 and 67Fcm−3). Significantly, the GN-PPy/CNT electrode shows excellent cycling stability (5% capacity loss after 5000 cycles) due to the flexible GN layer and the rigid CNT core synergistical releasing the intrinsic differential strain of PPy chains during long-term charge/discharge cycles. [Copyright &y& Elsevier]

Abstract: A film composed of graphene (GN) sheets, polyaniline (PANI) and carbon nanotubes (CNTs) has been fabricated by reducing a graphite oxide (GO)/PANI/CNT precursor prepared by flow-directed assembly from a complex dispersion of GO and PANI/CNT, followed by reoxidation and redoping of the reduced PANI in the composite to restore the conducting PANI structure. Scanning electron microscope images indicate that the ternary composite film is a layered structure with coaxial PANI/CNT nanocables uniformly sandwiched between the GN sheets. Such novel hierarchical structure with high electrical conductivity perfectly facilitates contact between electrolyte ions and PANI for faradaic energy storage and efficiently utilizes the double-layer capacitance at the electrode–electrolyte interfaces. The specific capacitance of the GN/PANI/CNT estimated by galvanostatic charge/discharge measurement is 569Fg−1 (or 188Fcm−3 for volumetric capacitance) at a current density of 0.1Ag−1. In addition, the GN/PANI/CNT exhibits good rate capability (60% capacity retention at 10Ag−1) and superior cycling stability (4% fade after 5000 continuous charge/discharge cycles). [Copyright &y& Elsevier]

Abstract: Nickel sulfide nanoparticles (NPs) are first synthesized by virtue of a unique H2O/CS2 interface under mild hydrothermal treatment. Electrochemical data reveals that the as-synthesized NiS NPs themselves own poor supercapacitive behavior at initial cyclic voltammetry (CV) cycles in 2M KOH solution, while a specific capacitance of 893Fg−1 can be surprisingly obtained at a current density of 5Ag−1 just after continuous 320 CV cycles. X-ray diffraction and Fourier transform infrared techniques demonstrate that what is really responsible for the good electrochemical capacitance in the KOH aqueous solution is the new electrochemically formed Ni(OH)2 phase, rather than NiS NPs themselves. The Ni(OH)2 is slowly formed during the continuous CV cycling process, in which the electrochemically induced phase transformation from NiS to Ni(OH)2 phase takes place. Furthermore, the new Ni(OH)2 phase demonstrates the great ability of delivering large specific capacitance at high rates. [Copyright &y& Elsevier]

Abstract: In the work, multi-walled carbon nanotubes (MWCNTs) were coated uniformly onto the cotton fibers to make porous conductive cotton textile, where MWCNTs formed an electrically conductive interconnecting network. Then, a flexible, lightweight, cheap and porous composite was synthesized for electrochemical capacitors (ECs) by dispersed pseudocapacitive cobalt hydroxide well onto the conductive cotton textile sheet. Electrochemical results show that the unique flexible and porous composite owns the ability to deliver large area specific capacitance of 11.22Fcm−2 and good electrochemical stability of 4% capacity loss after 2000 cycles at high rates. Moreover, the extremely simple design and fabrication process we proposed here provide a universal and efficient approach to large-scale production of flexible, lightweight, low-cost and porous electrode for ECs application. [Copyright &y& Elsevier]

Abstract: A novel and facile non-covalent process was applied to sulfonate multiwalled carbon nanotubes (MWCNTs) with a high –SO3H loading carbonaceous (C-SO3H). Then the sulfonated multi-walled carbon nanotubes/polypyrrole nanocomposite (MWCNTs/C-SO3H/PPy) was synthesized by the in situ chemical polymerization of pyrrole on the non-covalent sulfonated MWCNTs (MWCNTs/C-SO3H) using ammonium persulfate as oxidant at low-temperature. Fourier transform infrared (FT-IR) spectra confirm the modification of MWCNTs and an existence of interaction between the –SO3H group of the modified MWCNTs and the N–H group of PPy. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), FT-IR and ultraviolet–visible (UV–vis) spectra show that uniform PPy layer coated on the sidewall of MWCNTs/C-SO3H. The electrochemical properties of the MWCNTs/C-SO3H/PPy composite were studied by cyclic voltammetry and galvanostatic charge/discharge test. The composite possesses good rate response and stable specific capacitance, the specific capacitance loss is only 3% even after the 1000 cycles. [Copyright &y& Elsevier]

Abstract: In the work, short multi-walled carbon nanotubes (S-CNTs) were synthesized by chopping conventional μm-long multi-walled carbon nanotubes (L-CNTs) under ultrasonication in H2SO4/HNO3 mixed acids. A comparative electrochemical investigation performed in 6M KOH solution demonstrated that a specific capacitance (SC) of ca. 14.6μFcm−2 was delivered by the S-CNTs with the specific surface area (SSA) of 207m2 g−1, much larger than that of ca. 10.1μFcm−2 for the L-CNTs with the SSA of 223m2 g−1, the reason for which was that S-CNTs with two open ends, due to good ion penetrability, provided more entrances for electrolyte ions to access the inner surface easily through their shorter inner pathway so as to enhance their SSA utilization and geometric SC. The surface structure disruption of S-CNTs, owing to ultrasonication and oxidation during chopping process, deteriorated their electronic conductivity and resulted in an inferior power property in contrast to L-CNTs. [ABSTRACT FROM AUTHOR]

Abstract: This work describes an effective method to synthesize structurally uniform composite of nickel oxide/benzenesulfonic functionalized multiwalled carbon nanotubes composite (NiO/f-MWCNTs) using benzenesulfonic MWCNTs as the substrate. Benzenesulfonic group here is bifunctional both for solubilizing MWCNTs into aqueous solution and for tethering Ni2+ precursor onto MWCNTs surfaces to facilitate the follow-up chemical deposition of NiO by supplying surface binding and anchoring groups. The composite has a uniform surface dispersion and large coverage of NiO onto f-MWCNTs, which is characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscope, cyclic voltammetry and galvanostatic charge/discharge measurements. The NiO/f-MWCNTs composite improved the utilization of electrochemical capacitive materials and delivered capacity of 384F/g at the constant current of 0.20A/g due to f-MWCNTs as substrate. [Copyright &y& Elsevier]

Abstract: CeO2-modified LiFePO4 cathode was synthesized by using the triblock copolymer poly(ethylene oxide)–block–poly(propylene oxide)–block–poly(ethane oxide) (P123) as a template. CeO2-modified (2wt.%), 5wt.% CeO2-modified and pristine LiFePO4 powders were characterized by XRD and SEM measurements. The electrochemical behaviors were investigated by cyclic voltammetry measurements in Li2SO4 aqueous electrolyte. It was shown that all compounds undergone lithium-ion deintercalation and intercalation upon oxidation and reduction at different scan rates. The electrochemical lithium-ion deintercalation–intercalation processes of the CeO2-modified LiFePO4 electrodes were improved compare to the pristine LiFePO4 electrode, especially at elevated temperature and larger scan rates. 2wt.% CeO2-modified material showed better electrochemical performance than that of 5wt.% and pristine materials. A linear relationship between the peak current and the square root of scan rate for all peak pairs indicated that the Li+ deintercalation/intercalation processes occurred in all compounds were diffusion-controlled. The values of the 2wt.% CeO2-modified LiFePO4 electrode is much larger both at room temperature and 40°C. The electrochemical impedance spectroscopy tests were carried out before and after CV measurements. It was found that the CeO2 modification produced a good electrical contact between oxides, which was in very good agreement with the electrochemical behaviors of electrodes. The treatment with CeO2 should improve the comprehensive properties of the cathode materials for lithium-ion batteries at elevated temperature and larger scan rates. [Copyright &y& Elsevier]

Abstract: Mesoporous MnO2 has been synthesized by means of a novel, facile, and template-free method by virtue of a soft interface between CCl4 and H2O without any surfactants or organometallic precursors or ligands. X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy analysis, scanning electron microscopy, and an ASAP2010 autoadsorption analyzer were applied to investigate the composition and microstructure of the as-synthesized MnO2. The structure characterizations indicated a good mesoporous structure for as-prepared MnO2 with an adsorption average pore diameter of 9.7 nm, mesoporous volume of 0.58 cm3 g−1, and Brunauer–Emmett–Teller specific surface area of 239 m2 g−1. Electrochemical properties of the mesoporous MnO2 were elucidated by cyclic voltammograms, galvanostatic charge–discharge, and electrochemical impedance spectroscopy in 1 M Na2SO4 electrolyte. Electrochemical data analysis demonstrated that as-synthesized MnO2 had good capacitive behavior due to its unique mesoporous structure. A specific capacitance of ca. 220 F g−1 could still be delivered for the mesoporous MnO2 even at a scan rate of 100 mV s−1. [Copyright &y& Elsevier]

Abstract: Co-functionalized titanate nanotubes (Co-Ti-NTs) were successfully synthesized by means of an ion-exchange reaction. In contrast to the pristine titanate nanotubes (Ti-NTs), Co-Ti-NTs retained rich porous channels and owned even larger specific surface area and better electronic conductivity, which rendered electrons and OH− ions easily contact the Co species uniformly distributed on their surfaces for energy storage at high rates. The Co-Ti-NTs delivered a specific capacitance (SC) of 124Fg−1 at 0.4Ag−1, and a SC degradation of ca. 7% after 1500 continuous cycling at 3Ag−1, indicating that the Co-Ti-NTs were good candidates and/or even good supports for other electroactive materials for supercapacitors application. [Copyright &y& Elsevier]