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Abstract: A new electrode consisting of iron(III) hexacyanoferrate(II) known as Prussian blue and Dibenzo-18-crown-6 macrocycle ion-pair complex formed in presence of chloroform was studied for its electrochemical behavior in 0.1M KCl solutions. The ion-pair complex exhibited cyclic voltammetric response combining the Faradic redox characteristics of Prussian blue and the non-Faradic capacitance behavior of crown ether. Pseudo-capacitance values from the cyclic voltammetric measurements of the ion-pair complex showed a nine-fold increase as against the crown ether and a 1.5 times increase compared to Prussian blue. The ion-pair complex was chemically and electrochemically stable up to the cycled 1000 runs. Double potential step chronocoulometric measurements done at the lowest time scale of 10s showed specific capacitance value of 28.95×103 Fg−1 for the reduction step and 52.92×103 Fg−1 for the oxidation step. Such pseudo-capacitive values are the requisite of electrochemical capacitors that can provide huge power pulse within a very short time. [Copyright &y& Elsevier]

Abstract: Nano-thin polypyrrole (PPy) films were deposited on vapor grown carbon fibers (VGCF) by using an in situ chemical polymerization of the monomer in the presence of FeCl3 oxidant. An ultrasonic cavitational stream was used during polymerization of pyrrole, to enable the deposition of uniformly nano-thin PPy films on the surface of VGCF. The PPy/VGCF composite was characterized by FTIR spectroscopy. Surface morphology of the polymer films was characterized by using scanning electron microscopy and scanning transmission electron microscopy. The capacitance of the composite electrodes was investigated with cyclic voltammetry. As results of this study, thinner layer of PPy in the composite electrode (<10 nm) was effective to obtain fully reversible and very fast Faradaic reaction. Hence, most mass of the PPy could contribute to the pseudo-capacitive charge storage. This nano-thin PPy layer exhibited higher specific capacitance of ∼588 F g−1 at 30 mV s−1 and ∼545 F g−1 at 200 mV s−1 along with an excellent power capability. [Copyright &y& Elsevier]

Composite electrodes made of poly(3-methoxythiophene) (pMeOT) and activated carbon fiber (ACF) were prepared by electro-oxidation of 3-methoxy-thiophene in acetonitrile (AN). The SEM observation of the composites revealed that thin nano-structured polymer films were deposited on the surface of ACF, whose morphologies depended on the polymerization conditions. The electrochemical activities of the composites as capacitor electrodes were examined by cyclic voltammetry and galvanostatic cycling in AN. Capacitance enhancement was observed for both types of composite electrodes prepared differently. "Electrolyte impregnation method" brought about the pseudo-capacitance originated from the polymer on the ACF substrate. "Monomer impregnation method' increased the double-layer capacitance based on the porous structure of ACF. [ABSTRACT FROM AUTHOR]

Multi-layer and co-deposition composite electrodes were prepared by introducing the carbon powders into the anodically deposited hydrous manganese oxide. The surface morphology and crystal structure of the electrodes were examined by scanning electron microscope and glancing angle X-ray diffraction. Cyclic voltammetrty and chronopotentiometry were also performed to evaluate the electrochemical characteristics of the electrodes prepared. These composite electrodes with rough surface, consisted of amorphous hydrous manganese oxide and carbon powder, were confirmed to possess the ideal capacitive property. The specific capacitance, high power capability and cyclic stability of the hydrous manganese oxide/carbon composite electrodes were superior to that of the plain hydrous manganese oxide electrode. [Copyright &y& Elsevier]

Ruthenium/carbon composite materials are prepared by impregnating ruthenium(III) acetylacetonate into a mesoporous carbon (average pore diameter=12 mn, pore volume=3.6 cm3 g−1) and then heat treatment at 320 °C for 2 h under an argon atmosphere. The metallic ruthenium nanoparticles are converted to pseudo-capacitive hydrous ruthenium oxide by electrochemical oxidation at 0.75 V (versus SCE) for 2 h in 2.0 M H2SO4. The specific capacitance of the composite electrodes, which is the sum of the double-layer capacitance of mesoporous carbon and the pseudo-capacitance of hydrous ruthenium oxide, reaches 243 F g−1 with heavy loading. As the loading is increased, however, the degree of ruthenium utilization for a pseudo-capacitor becomes poorer, presumably due to a limited conversion to the hydrous oxide form. The rate capability of composite electrodes also decreases with increase in ruthenium loading, due to an increase in both the equivalent series resistance (ESR) and the overall capacitance value.The ESR enlargement is caused mainly an increase in the electrolyte resistance within pores which, in turn, results from a pore narrowing with ruthenium loading Hindered ionic motion in narrowed pores can explain this feature. An increase in the RC time constant with ruthenium loading is further verified by ac impedance measurements. [Copyright &y& Elsevier]

The capacitive behaviours of magnetite nanocrystallites, along with conductive carbon black additive, in aqueous electrolytes, including sodium sulphite, sulphate, chloride, and phosphate, and potassium hydroxide, have been characterised by means of cyclic voltammetry and chrono-potentiometry. The behaviour can be categorised into three groups. Sodium sulphate and chloride electrolytes give capacitances (∼5 F/g-Fe3O4) close to the space-charge capacitance of the oxide. Potassium hydroxide and sodium phosphate gave rise to a higher capacitance (∼7 F/g) which can in part be attributed to a surface redox reaction which involves hydroxide ions. Sodium sulphite results in the highest capacitances, which depend heavily on the dispersion of magnetite crystallites on the conductive matrix and range from ∼30 to 510 F/g-Fe3O4 with an operation voltage range of 1.2 V. Correlation between rest potential and anion-concentration gives strong indication of potential-determining process which involve either OH under extremely alkaline conditions (pOH<3) or SO32− in the sulphite electrolyte. [Copyright &y& Elsevier]

The specific capacitance of activated carbons is determined by both the ratio of edge/basal orientation and the nature of functional group on the surface. The difference between the edge and the basal layers results from the semiconductive properties of basal layer. The ratio of edge/basal orientation can be estimated by X-ray diffraction (XRD). The wettability of activated carbons is determined by the nature of functional groups on the surface. Most of the surface groups are electrochemically active. The impact of the surface groups on electrochemical performance of the activated carbon electrodes was investigated by means of various surfactant treatments. The ac impedance and constant current discharge techniques were used. Two types of surface groups which had “capacitor-like” or “battery-like” behaviors, respectively, were revealed and discussed in detail. The surface groups with “battery-like” behavior should be avoided. “Non-symmetric” electrode arrangement should be considered for a double-layer supercapacitor in order to take the advantages of pseudo-capacitance of the surface groups with “capacitor-like” behaviors. [Copyright &y& Elsevier]

The redox-active electrolytes can cost-effectively enhance the energy densities of energy storage devices, which, however, face the challenge of short cycle-life and poor compatibility to device electrodes. Here, redox-active hydrogels can be facilely prepared with promising proton conductivities and electrode compatibility from the supramolecular complexation of neomycin sulfate and metal oxide clusters. Metal oxide clusters serve as both proton and electron reservoirs to simultaneously improve the proton conductivities of electrolytes and super redox properties for the pseudo-capacitance, leading to the enhancement of the energy densities of supercapacitors. Proton conduction follows typical Grotthuss mechanism through the fast dynamic arrangement of hydrogen bonding networks among water, neomycins and metal oxide clusters. With activated carbon as electrodes, the assembled supercapacitors of the hydrogels show excellent cycle stabilities. The supramolecular complexation of reversible redox active cluster opens an avenue for facile assemblies of highly efficient and robust super-capacitors. Metal oxide clusters as proton and electron reservoirs are complexed with neomycin sulfate into hydrogel, which serves as the redox-active proton conductor in supercapacitor. The redox reversibility of metal oxide clusters not only enhances the energy density of supercapacitor, but also ensures the supercapacitor with the electrochemical stability. [Display omitted] [ABSTRACT FROM AUTHOR]

• N and B co-doped densified LIG is prepared based on duplicate laser pyrolysis. • The effects of H 3 BO 3 loadings and laser pyrolysis power on LIG are investigated. • NB-dLIG shows remarkable capacitive enhancement compared to N-dLIG and undoped-sLIG. This study demonstrates a facile and versatile approach to the fabrication of N and B co-doped and simultaneously densified laser-induced graphene (NB-dLIG) based on a duplicate laser pyrolysis method for supercapacitor applications. The LIG obtained after the first laser pyrolysis is coated with an additional thin layer of polyamic acid /H 3 BO 3 and additionally irradiated with a laser, resulting in the simultaneous densification and incorporation of N and B heteroatoms into the graphene-like structure of LIG. The NB-dLIG with optimized H 3 BO 3 loading (1 wt%) and duplicate laser power (2.4 W; NB1-dLIG-2.4) exhibits remarkably improved capacitive performance due to the synergistic effect of N and B co-doping. The NB1-dLIG-2.4 electrode delivers a specific areal capacitance (C A) of 104.3 mF/cm2, which is nearly 2.5 and 12 times higher than N-doped dLIG (42.4 mF/cm2) and undoped single pyrolyzed LIG (9.0 mF/cm2), respectively, at 0.2 mA/cm2 using a three-electrode assembly. Furthermore, a solid-state flexible supercapacitor is fabricated with NB1-dLIG-2.4 and PVA-H 2 SO 4 gel electrolyte, attaining a high C A (40.4 mF/cm2 at 0.05 mA/cm2), with excellent cycling stability, Coulombic efficiency, and mechanical flexibility. This work opens a new avenue for fabricating LIG doped with multiple heteroatoms, which can be used in various electrochemical applications. [ABSTRACT FROM AUTHOR]

• Fe nanoparticles embedded graphitic nanoribbons (Fe@GNR) was prepared by sol-gel method and catalytic graphitization. • Iron ions served trifunctional properties including oxidizing agent, graphitizing catalysts and active materials. • The core-shell structure is the key reason for the high reversible capability of almost 100%. [Display omitted] A graphitic nanoribbons (GNRs) encapsulated with Fe nanoparticles (NPs) hybrids derived from pyrrole and FeCl 3 through polymerization, freeze drying and catalytic graphitization process showed excellent capacitive and cycle performance using as pseudo-capacitive material for supercapacitors (SC). The precursor of FeCl 3 ingeniously served as oxidant for polymerization of pyrrole, catalyst for graphitization of polypyrrole and pseudo-capacitive material for SC successively. The obtained Fe@GNRs electrode exhibited a remarkable pseudocapacitance performance with a high specific capacitance of 526.7 F g−1 at a discharge current density of 1 A g−1. GNRs obtained by catalytic graphitization of polypyrrole under metallic Fe could effectively protect and stabilize the encapsulated Fe NPs showing ~100% capacitance retention rate after 10,000 cycles under 10 A g−1. [ABSTRACT FROM AUTHOR]

Transition-metal oxides and phosphates can engage oxidation states that enhance reduction-oxidation (redox) reactions and can lead to excellent pseudo-capacitance behavior. In this study, amorphous Ar–Co 3 (PO 4) 2 (Ar ​= ​amorphous) was combined with the mixed valence cobalt oxide Co 3 O 4 (or CoIICoIII 2 O 4) to form a composite with a higher specific capacitance (531. 4 ​F/g) than pure Co 3 O 4 (302.8 ​F/g) at 3 ​mV/s in 3 ​M KOH. The material was synthesized using an in-situ precipitation reaction of ammonium cobalt phosphate on Co 3 O 4 followed by thermal treatment at 550 ​°C. Studies into the mechanism showed improved charge storage was linked to Co 3 O 4 having rapid redox reactions on its surface. Cyclic stability studies revealed that the Ar–Co 3 (PO 4) 2 /Co 3 O 4 composite showed better stability with capacitance retention of 89.1% than when compared to pure Co 3 O 4 at 76.5%. Both pure Co 3 O 4 and Ar–Co 3 (PO 4) 2 /Co 3 O 4 contain mesopores with the former having a larger average pore volume. These findings demonstrate the potential of Ar–Co 3 (PO 4) 2 and Co 3 O 4 as a promising electrode composite material in the fabrication of high-performance supercapacitor devices. Amorphous Co 3 (PO 4) 2 and crystalline Co 3 O 4 composites with a high specific capacitance compared to single-phase crystalline Co 3 O 4 was prepared from NH 4 CoPO 4 ·H 2 O/Co 3 O 4. [Display omitted] • Amorphous Co 3 (PO 4) 2 and the spinel CoIICoIII 2 O 4 formed a composite by an in-situ precipitation reaction. • The formed composite had a higher specific capacitance (531. 4 ​F/g) than pure Co 3 O 4 (302.8 ​F/g). • Mechanism studies showed improved charge storage was linked to Co 3 O 4 redox surface reactions. • Cyclic stability studies revealed the composite showed good stability with capacitance retention of 89.1%. • Both pure Co 3 O 4 and Co 3 (PO 4) 2 /Co 3 O 4 contain mesopores with the former having a larger average pore volume. [ABSTRACT FROM AUTHOR]

A flexible MnO 2 /p-Ti 3 C 2 T x hybrid film with porous Ti 3 C 2 T x nanosheets and intercalated MnO 2 nanoshells was prepared used directly as pseudo-capacitive electrode, which showed unique porous structure that accelerated the ion transport in vertical and in-plane directions by the nanopores in the intra-layer and inter-layer of Ti 3 C 2 T x nanosheets and achieved higher capacitance. [Display omitted] • A flexible MnO 2 /Ti 3 C 2 T x hybrid film composed of alternately arranged porous Ti 3 C 2 T x nanosheets and MnO 2 nanoshells. • The unique porous structure of the film facilitated the ion transport both in the vertical and in-plane directions. • Specific capacitance and cycle stability of the hybrid film were dramatically improved. A flexible MnO 2 /Ti 3 C 2 T x hybrid film was prepared and used directly as pseudo-capacitive electrode for supercapacitors, composed of alternately arranged porous Ti 3 C 2 T x nanosheets and MnO 2 nanoshells. The unique porous structure of the film facilitated the ion transport both in the vertical and in-plane directions by the nanopores in the intra-layer and inter-layer of Ti 3 C 2 T x nanosheets. And the specific surface area, specific capacitance and cycle stability of the hybrid film were dramatically improved compared with those of MnO 2 nanoshells and porous Ti 3 C 2 T x nanosheets. [ABSTRACT FROM AUTHOR]

SiOx is considered as a promising anode for next-generation Li-ions batteries (LIBs) due to its high theoretical capacity; however, mechanical damage originated from volumetric variation during cycles, low intrinsic conductivity, and the complicated or toxic fabrication approaches critically hampered its practical application. Herein, a green, inexpensive, and scalable strategy was employed to fabricate NG/SiOx/NG (N-doped reduced graphene oxide) homogenous hybrids via a freeze-drying combined thermal decomposition method. The stable sandwich structure provided open channels for ion diffusion and relieved the mechanical stress originated from volumetric variation. The homogenous hybrids guaranteed the uniform and agglomeration-free distribution of SiOx into conductive substrate, which efficiently improved the electric conductivity of the electrodes, favoring the fast electrochemical kinetics and further relieving the volumetric variation during lithiation/delithiation. N doping modulated the disproportionation reaction of SiOx into Si and created more defects for ion storage, resulting in a high specific capacity. Deservedly, the prepared electrode exhibited a high specific capacity of 545 mAh g−1 at 2 A g−1, a high areal capacity of 2.06 mAh cm−2 after 450 cycles at 1.5 mA cm−2 in half-cell and tolerable lithium storage performance in full-cell. The green, scalable synthesis strategy and prominent electrochemical performance made the NG/SiOx/NG electrode one of the most promising practicable anodes for LIBs. [ABSTRACT FROM AUTHOR]

• HNb 3 O 8 has better electrochemical performance than MNb 3 O 8 (M=K, Li, Na). • The reasons why HNb 3 O 8 has better performance than others are analyzed from the phase structure. • The charge/discharge specific capacity of HNb 3 O 8 will stabilize at 394.1/426.8 mAh g−1 at 0.1 C and the Coulombic efficiency are 91.99% after fifth cycle. Niobium-based materials have always been regarded as outstanding anode materials due to its capability of multiple electron transfer. Here, layered polyniobate MNb 3 O 8 (M=H, Li, Na) was prepared by ion-exchange of precursors KNb 3 O 8. HNb 3 O 8 present an excellent charge/discharge capacity of 394.1 mAh g−1/426.8 mAh g−1 at 0.1 C and the Coulombic efficiency is 91.99% after fifth cycle. Even after 60 cycles, it still retains substantial discharge specific capacities of 148.7 mAh g−1 at 0.5 C. In addition, by employing technics including XRD, Raman and XPS, HNb 3 O 8 are demonstrated to possess a larger interlayer channel of 1.11 nm and a stronger binding energy to foreign electrons than MNb 3 O 8 (M=K, Li, Na). This properties could justify the best electrochemical performance of HNb 3 O 8. EIS analysis also reveal that HNb 3 O 8 has the smallest charge transfer impedance among all the samples. All these advantages suggest that HNb 3 O 8 can be an alternative anode material for next generation lithium-ion batteries (LIBs). [ABSTRACT FROM AUTHOR]

The problem of voltage dynamics description in a circuit containing resistors, and at least two fractional order elements such as supercapacitors, supplied with constant voltage is addressed. A new operator called Conformable Derivative in the Caputo sense is used. A state solution is proposed. The considered operator is a generalization of three derivative definitions: classical definition (integer order), Caputo fractional definition and the so-called Conformable Derivative (CFD) definition. The proposed solution based on a two-parameter Conformable Derivative in the Caputo sense is proven to be better than the classical approach or the one-parameter fractional definition. Theoretical considerations are verified experimentally. The cumulated matching error function is given and it reveals that the proposed CFD–Caputo method generates an almost two times lower error compared to the classical method. [ABSTRACT FROM AUTHOR]

For the proliferation of the supercapacitor technology, it is essential to attain superior areal and volumetric performance. Nevertheless, maintaining stable areal/volumetric capacitance and rate capability, especially for thick electrodes, remains a fundamental challenge. Here, for the first time, a rationally designed porous monolithic electrode is reported with high thickness of 800 µm (46.74 mg cm -2 , with high areal mass loading of NiCo 2 S 4 6.9 mg cm -2 ) in which redox-active Ag nanoparticles and NiCo 2 S 4 nanosheets are sequentially decorated on highly conductive wood-derived carbon (WC) substrates. The hierarchically assembled WC@Ag@NiCo 2 S 4 electrode exhibits outstanding areal capacitance of 6.09 F cm -2 and long-term stability of 84.5% up to 10 000 cycles, as well as exceptional rate capability at 50 mA cm -2 . The asymmetric cell with an anode of WC@Ag and a cathode of WC@Ag@NiCo 2 S 4 delivers areal/volumetric energy density of 0.59 mWh cm -2 /3.93 mWh cm -3 , which is much-improved performance compared to those of most reported thick electrodes at the same scale. Theoretical calculations verify that the enhanced performance could be attributed to the decreased adsorption energy of OH - and the down-shifted d-band of Ag atoms, which can accelerate the electron transport and ion transfer., (© 2021 Wiley-VCH GmbH.)

The reduction extent of reduced graphene oxide plays a critical role in determining the energy storage performance when it is used as supercapacitor electrodes. Despite the increasing interest in graphene oxide (GO) reduction using flash, the relationship between reduction extent of flash-reduced GO (FRGO) electrodes and the supercapacitor performance remains elusive, which hinders the realization of supercapacitors with optimum performance. In this work, we present a comprehensive study on how reduction extent of FRGO electrodes can influence their properties and hence electrochemical performance. By controlling flash power, the reduction extent of FRGO materials can be finely tuned. The key electrode properties, namely the carbon-to-oxygen (C/O) atomic ratio or oxygen content, the porosity, and the electrical conductivity are characterized and analyzed in a coherent way. Surprisingly, we found that optimal electrode specific capacitance (166.7 F g−1) and supercapacitor energy density (78 W h kg−1) have been achieved when the C/O atomic ratio is relatively low at the flash light reduction threshold. In this case, despite not having the largest specific surface area and conductivity, the high oxygen content in such FRGO substantially contributes to capacitance through redox reactions with electrolyte. The present work has significant implication for developing supercapacitors with optimum performance. Image 1 • The optimal specific capacitance is achieved when C/O atomic ratio is relative low. • Residual oxygen-containing functional groups induce significant pseudo-capacitance. • The best performance of pure flash-generated RGO supercapacitor is reported. [ABSTRACT FROM AUTHOR]

Developing highly efficient electrochemical desalination techniques with both high salt removal capacity as well as sufficient longterm durability is urgently required in settling the global water crisis. Herein, we developed a high-performance hybrid capacitive deionization (HCDI) through the deployment of freestanding, Mn 2 O 3 nanoflower decorated carbon nanofibers (CNF@Mn 2 O 3) with pseudo-capacitive behavior as the electrode. The CNF@Mn 2 O 3 synthesized via electrospinning and in-situ deposition of Mn 2 O 3 shows both excellent pseudo-capacitive performance and freestanding nanostructure, which enables the CNF@Mn 2 O 3 -based HCDI system to exhibit superior desalination performance(27.43 mg∙g−1) as well as long-term stability (14.3% declination for 30 cycles). Such outstanding desalination performance should be ascribed to the high pseudo-capacitance, excellent charge transfer performance, and the freestanding nature of the CNF@Mn 2 O 3. This study is interesting because it exemplifies the importance of designing pseudo-capacitive electrode materials for constructing a high-performance HCDI system, which could cast light on the further development of high-efficiency electrochemical desalination systems. Highly-efficient hybrid capacitive deionization system is developed based on utilizing freestanding Mn 2 O 3 nanoflower decorated carbon nanofibers as electrode material. Unlabelled Image • Freestanding Mn 2 O 3 nanoflower coated carbon nanofibers (CNF@Mn 2 O 3) was fabricated. • Pseudo-capacitive CNF@Mn 2 O 3 was used for novel hybrid capacitive deionization. • The CNF@Mn 2 O 3 -based HCDI exhibits excellent desalination capacity of 27.43 mg∙g−1. • The HCDI displays superior long-term stability (14.4% declination after 30 cycles) [ABSTRACT FROM AUTHOR]

• Few-layered crumpled porous N-doped graphene was prepared using nitroaromatic molecules as N sources. • Nitroaromatic molecules effectively suppressed the aggregation of N-doped graphene. • As-obtained 5-NIGN had high specific capacitance of 457.4 F g−1 and long cycle life. Nitroaromatic pollutants with unusually strong adsorption affinity are highly attractive candidates for creating 2D molecular assemblies on the surface of graphene, which is crucial to prepare high-quality N-doped graphene by post-treatment. Herein, the few-layered crumpled N-doped graphene (5-NIGN) with high N content is successfully prepared by mixing 5-nitroindole (5-NI), ammonia, and graphene oxide (GO) and using a simple hydrothermal method followed by the post-treatment process of vacuum freeze-drying and annealing. It is found that the rapid assembly of 5-NI effectively suppresses the aggregation of the products in the reduction process of GO, so that the thickness of as-prepared 5-NIGN is 4.21 nm, very close to that of GO (4.01 nm). Compared with the N-doped graphene (GN) derived from the system of GO containing ammonia (341 F g−1), 5-NIGN exhibits higher capacitance of 457.4 F g−1 at 1 A g−1 and prominent long-term life (115% of capacitance maintenance upon 10,000 cycles) within the voltage window of 1.0 V. Furthermore, the supercapacitor assembled by 5-NIGN electrodes can deliver the energy density of 15.5 Wh kg−1~18.5 Wh kg−1 at the power density of 8000 W kg−1~800 W kg−1. These results indicate that the 5-NIGN material will have potential advantages in the realm of electrochemical energy storage. Image, graphical abstract [ABSTRACT FROM AUTHOR]

NiCo 2 S 4 (NCS) is a ternary spinel sulfide widely applied in supercapacitors and hybrid supercapacitors. Several electrochemical reaction formulas have so far been proposed in last decade. However, the energy storage mechanism and electrochemical behavior of NCS in alkaline electrolytes are still not fully understood. In this study, the interactions between hydroxide and NCS with low crystallinity are investigated through electrochemical testing and both surface and structure characterization. Compared to previous reports, electrochemical desulfurization is first introduced in electrochemical charge storage to reveal the intrinsic energy-storage mechanism of NCS in alkaline electrolyte. The highest specific capacitance of NCS reaches 666.27 F g−1 at 5 A g−1, originating from the irreversible phase transition during the activation process. The long cycle stability retains 65.29% of the highest specific capacitance after 10 000 cycles, attributed to the transformation product (nickel-cobalt dihydroxide) without further phase change after the activation process. In sum, clarification of the intrinsic energy-storage mechanism of NCS with low crystallinity can be helpful for future preparation of anode materials for applications in alkaline supercapacitors, batteries, and hybrid devices. • Sulfur leaching occurring in cyclic service of NiCo 2 S 4 as an anode material. • NiCo 2 S 4 transforming into Ni–Co layered double hydroxide during cyclic service. • Its pseudo-capacitance behavior belonging to Ni–Co layered double hydroxide. • Desulfurization introduced into the energy-storage mechanism of NiCo 2 S 4. • Composite design strategy proposed to improve the stability of NiCo 2 S 4. [ABSTRACT FROM AUTHOR]

The article presents abstracts of research related to polymers. They include "Research and Development of All Solid-State Lithium Polymer Secondary Batteries," "Development of Fluoropolymer Electrolyte Membranes for Fuel Cell Applications by the y-Ray Induced Crosslinking and Graft Polymerization Methods" and "Novel Electrocatalysts for Oxygen Reduction Using Cobaltporphyrins That Undergo Facile Electropolymerization."

The effect of the solvent used in the chemical polymerization of pyrrole on the electrochemical pseudo-capacitance properties of the material is investigated by means of cyclic voltammetry. Electro-conducting polypyrroles (PPy) are prepared in the presence of various solutions such as H2O, diethyl ether, and acetonitrile (ACN). The PPy powder prepared in H2O exhibits the largest capacitance value, approximately 355 F g−1, in ACN solution containing 1 M tetraethylammonium tetrafluoroborate (TEABF4). This dependency on solvent is directly related to the surface roughness of PPy powder. [Copyright &y& Elsevier]