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The voltammetric behavior of the Ce(III)/(IV) half-cell reaction in various electrolytes containing 0.6 M Ce was investigated on both pristine and metal-modified carbon paper (CP) electrodes at three different temperatures (25, 40 and 55 °C) in order to find the most favorable electrochemical conditions. The pristine CP displayed robust electrochemical performance for up to 200 repetitive CV cycles while the Pt loaded electrode’s performance was stable for only 70 cycles, even though the latter exhibited a more reversible behavior, moving from a quasi-reversible to a reversible system ( D ox. = 4.0 × 10 −6 cm 2 s −1 and D red. = 2.5 × 10 −6 cm 2 s −1 ). The In and La metal modified electrodes did not show any improvement with regard to the kinetics or reversibility of the reaction. The addition of 1 M H 2 SO 4 to the base electrolyte enhanced the cerium reduction reaction by a factor of 3, ( −7.2 × 10 −3 A cm −2 ). The highest exchange current densities (j o ) were achieved at 40 °C for the CP-Pt (1 × 10 −3 A cm −2 ) attributable to the presence of the catalytic Pt. Elevated temperatures (40 and 55 °C) improved D and ΔE p. while also the mass transport parameters a) dynamic viscosity (∼1.5 mPa·s) and b) electrolytic conductivity (∼265 mS cm −1 ) of the Ce(III)/(IV) half-cell reaction. Overall, pristine CP and to a lesser extent CP-Pt demonstrated good stability with prolonged cycling and kinetics comparable with the ones of Pt and Pt based electrodes. [ABSTRACT FROM AUTHOR]

Although functionalized carbon-based materials have been widely used as the supercapacitor electrodes, the optimum contents of the functional groups, the charge storage mechanisms, and the effects of electrolytes and operating temperature have not yet been clearly investigated. In this work, carboxylate-modified hollow carbon nanospheres (c-HCN) with different functional group contents synthesized by an oxidation process of carbon nanospheres with nitric acid were coated on flexible carbon fibre paper and used as the supercapacitor electrodes. An as-fabricated supercapacitor of the c-HCN with a finely tuned 6.2 atomic % of oxygen of the oxygen-containing groups in an ionic liquid electrolyte exhibits a specific capacitance of 390 F g −1 , a specific energy of 115 Wh kg −1 , and a maximum specific power of 13548 W kg −1 at 70 °C. The charge storage mechanism investigated is based on the chemical adsorption of the ionic liquid electrolyte on the c-HCN electrode. This process is highly reversible leading to high capacity retention. The supercapacitor in this work may be practically used in many high energy and power applications. [ABSTRACT FROM AUTHOR]

Abstract: This paper focuses on an understanding of the influence of paper thickness on the electrochemical performances of graphene papers as an anode for lithium ion batteries. Three types of graphene papers, with thickness of ∼1.5, 3 and 10μm, respectively, were fabricated by vacuum-assisted filtration of reduced graphene nanosheets suspended in water. These papers deliver evidently different lithium storage capacities, with thinner papers always outperform thicker ones. The 1.5μm paper gives rise to initial reversible specific capacities (the first 10 cycles) of ∼200mAhg−1 at a current density of 100mAg−1, while the 10μm paper only presents ∼80mAhg−1 at a current density of 50mAg−1. After 100 cycles, a specific capacity of ∼180mAhg−1 is retained for the 1.5μm paper; in contrast, only ∼65mAhg−1 remains for the 10μm paper. The capacity decline with the paper thickness is associated with the dense restacking of graphene nanosheets and a large aspect ratio of the paper. The effective Li+ diffusion distance in graphene paper is mainly controlled by the thickness of the paper, and the diffusion proceeds mainly in in-plane direction, cross plane diffusion is restrained. As such, the effective contact of graphene nanosheets with electrolyte is limited and the efficiency of carbon utilization is very low in the thick papers. [Copyright &y& Elsevier]

Abstract: Symmetric paper-based supercapacitor devices containing polypyrrole (PPy)–cellulose composite electrodes and aqueous electrolytes can be charged using either potential step or constant current charging. Potential step charging provides better control of the charging and can result in significantly shorter charging times, enabling charging in 22s for devices with cell capacitances of 12.2F when charged to 0.8V. The paper-based electrode material was compatible with charging currents as large as 5.9Ag−1 due to the rapid counter ion mass transport resulting from the porous composite structure and the thin PPy coatings. The charging times were controlled by the RC time constants of the devices and the cell resistance was found to decrease with increasing electrode area. For small cells, the cell resistance was determined to a large extent by the electrolyte resistance and contact resistances, whereas the resistance of the current collectors dominated for larger cells. The specific cell capacitance was 38.3Fg−1 or 2.1Fcm−2, normalized with respect to the total electrode weight and electrode cross section area respectively, and the devices showed 80–90% capacitance retention after 10000 potential step charge and discharge cycles. These results, which demonstrate that potential step charging can be advantageous for conducting polymer based energy storage devices, are very encouraging for the development of new up-scalable paper-based energy storage devices. [Copyright &y& Elsevier]

This paper presents an exhaustive how-to guide on measuring the total vanadium concentration and state of charge of vanadium electrolytes using UV–Visible spectroscopy. The study is provided with an open-access database (GitHub) that supports the methods and procedures and facilitates access to the calibration data. The study covers the three types of electrolyte solutions relevant to vanadium redox flow batteries, namely the anolyte V II / V III , the catholyte V IV / V V , and the V III / V IV commercial electrolyte, meant to be preconditioned to either V III or V IV before battery operation. Analytical expressions to calculate the concentration of different vanadium species in the electrolyte solutions are provided based on either empirical correlations or spectral deconvolution methods. The paper also examines the limitations of the measurement technique and provides insightful recommendations for future research. The open-access database provided by the authors is expected to serve as a valuable repository for scholars and scientists working in the field of vanadium redox flow batteries. • UV–Visible spectroscopy is used to characterize vanadium electrolytes. • We studied the anolyte V II / V III , the catholyte V IV / V V , and V III / V IV . • An empirical method and a deconvolution method are proposed for each electrolyte. • The methods are calibrated over a wide range of concentrations (0.91–1.83M). • Total vanadium concentration and state of charge can be accurately measured. • Accuracy is 25–35 mM for the concentration and 1.0–1.5% for the state of charge. [ABSTRACT FROM AUTHOR]

Electrochemical permeation tests are used to investigate the diffusion and trapping effects of hydrogen in a metal. For a quantitative and reliable evaluation of these features, the development of a numerical model is required. In the first paper of this series, we developed a model describing the hydrogen transport process in the Devanathan-Stachurski cell and evaluated the influence of the entry interface on the experimental results. Although many models have already been proposed for the description of the hydrogen diffusion in the Devanathan-Stachurski cell, none of them is including the simulations of the anodic side of the cell. In this paper, we present a new model representing the Devanathan-Stachurski cell. With this model, we are able to make a sensitivity analysis of all the parameters that play a role during the hydrogen diffusion process in iron alloys, comprising the adsorption, absorption, diffusion and desorption processes that the hydrogen undertakes in the sample mounted in the Devanathan-Stachurski cell. In particular, we found that the common assumption of constant zero concentration at exit side broadly accepted by researchers may not always reflect the real situation and the evaluation of the desorption process as often used today might be oversimplified. Certainly, the complexity of the desorption/oxidation is of high degree when Pd coating is not applied at the exit side. Consequently, the effect of the anodic electrolyte and the surface state at exit side should be considered as a significant element affecting the experimental results. [ABSTRACT FROM AUTHOR]

Electrochemical ammonia production from molecular nitrogen and nitrate reduction reactions at ambient conditions has gained a lot of attention in recent years, making this topic more and more appealing. The race towards good and quick results in terms of Faradaic efficiency and productivity is not always focused on the possible source of ammonia contamination. In particular, Nafion membrane is the most commonly used in this field as cell separator, discarding the possible known disadvantages coming from ammonium ions absorption and release. The wettable microporous Celgard membrane has been proposed as a substitute for Nafion membranes, despite the separation mechanism, in this case, is only dimension-driven, so it does not assure ammonium ions retention. This paper reveals that the mechanism of ammonium ions absorption and release by Nafion 117 is strongly related to the cations present in the electrolyte and to a lesser extent by its pH value. On the other hand, Celgard membrane does not show any relevant ammonium ions absorption. Moreover, the different trend of ammonium ions motion from catholyte to anolyte solution inside a flow-cell reactor shows that none of the membranes is able to avoid ammonium ions crossover and that there is a correlation between the applied potential and the motion trend. Electrochemical nitrogen and nitrate reduction tests confirm how Nafion membrane can have a big impact on the final result of ammonium ions production, especially when dealing with low production quantities, leading to mistakes in the real quantity of ammonium ions coming from the reduction reaction. [ABSTRACT FROM AUTHOR]

Further increasing the output power is important to develop next-generation supercapacitor. In recent years, many papers focus on the design of pore structure to improve high-rate performance of supercapacitor, but few reports devote attention to reducing the nanoscale size of carbon framework to reach an optimal ion transfer. In the present paper, a novel ultrathin carbon gauze was fabricated by a simple boiling-induced volume expansion method. This carbon gauze shows foam-like morphology that is composed of 7 nm-thick carbon sheets. In addition, owing to the loose stack of carbon sheets, lots of meso-/macropores are created. When used as electrode in supercapacitor, the ultrathin carbon sheets can effectively minimize the electrolyte transfer distance and meso-/macropores can accelerate ion transfer speed, and then carbon gauze exhibits an impressive high-rate supercapacitive performance. While the scan rate is raised from 0.02 to 0.5 V s −1 , the capacitance only reduces from 190 to 173 F g −1 , implying a retention of 91%, and even under an extremely high scan rate of 2.0 V s −1 , the cyclic voltammogram of carbon gauze still presents a symmetrically rectangular shape, revealing a considerable capacitance of 142 F g −1 (75% of the capacitance at 0.02 V s −1 ). [ABSTRACT FROM AUTHOR]

Understanding the chemical reactions that occur during lead-acid battery aging is useful for predicting battery life and repairing batteries for reuse. Current research on lead-acid battery degradation primarily focuses on their capacity and lifespan while disregarding the chemical changes that take place during battery aging. Motivated by this, this paper aims to utilize in-situ electrochemical impedance spectroscopy (in-situ EIS) to develop a clear indicator of water loss, which is a key battery aging process and could be repaired, through unique water loss experiments. These experiments were designed to ensure that the percentage of water in the electrolyte or the volume of electrolyte was the only factor that affected in-situ EIS in each experiment, and these values were regularly changed to simulate water loss in a specially designed transparent lead-acid battery. Through an improved equivalent circuit model (ECM) and grey relation analysis (GRA), this work shows that the variation of double-layer capacity and internal resistance can indicate added water content and electrolyte volume. The developed method is simple and can be applied to identify and respond to battery water loss effectively. [ABSTRACT FROM AUTHOR]

In this paper the dependence of the elemental and phase compositions of the binary A-B cathodic deposits are computed by constructing "Electrochemical Diagrams", abbreviated as ECDs, which potentially have a high practical significance. An ECD shows phases and compositions of cathodic alloy products as function of electrolyte composition at fixed temperature, pressure and at low current density upon galvano-static electrochemical co-deposition of components A-B from the same electrolyte on an inert cathode. The following rules are established here to construct the ECDs for binary A-B alloys: i). among all possible cathodic phases the one will be electrodeposited that provides the least negative cathodic deposition potential, ii). two or three (but not four or more) phases can be co-deposited on the cathode if their equilibrium cathodic potentials are equal and are the least negative among all possible cathodic phases, iii). the equilibrium compositions of solid and liquid A-B alloys that form on the cathode can be found from the condition of equality of the partial equilibrium cathodic potentials of components A and B. Based on the above three rules, ECDs are constructed for some basic types of binary equilibrium alloy phase diagrams with the composition of the alloy on its y -axes as function of the ionic composition of the electrolyte on its x -axes. In all cases the clear connection is shown between the ECDs and their corresponding alloy phase diagrams. The following geometric features are established for ECDs: i). solution phases are characterized by continuous curves, ii). phases of fixed compositions are characterized by horizontal lines, iii). two-phase mixtures are characterized by vertical lines, iv). three-phase equilibria are characterized by single points along the vertical lines corresponding to the two-phase equilibria of the parent phases of the third phase. It is shown that the restricted phase rule of Gibbs (= the maximum number of coexisting phases = the number of independent components + 1) is valid also for the ECDs. As examples, ECDs are calculated for the Ni-Co system and for the Ti-B system and good agreement is found between these calculated diagrams and the experimental data. [Display omitted] [ABSTRACT FROM AUTHOR]

The slow power tracking, operating safety, especially the fuel exhaustion, and high efficiency considerations are the key issues for integrated solid oxide fuel cell (SOFC) systems during power step up transients, resulting in the relatively poor dynamic capabilities and make the transient load following very challenging and must be enhanced. To this end, this paper first focus on addressing the efficiency optimization associated with simultaneous power and thermal management of a 5-kW SOFC system. Particularly, a traverse optimization process including cubic convolution interpolation algorithm are proposed to obtain optimal operating points (OOPs) with the maximum efficiency. Then this paper investigate the current implications on system step-up transient performance, then a two stage pre-conditioning current strategy and a feedback power reference control scheme is proposed for load step-up transients to balance fast load following and fuel starvation, after that safe thermal transient is validated. Simulation results show the efficacy of the control design by demonstrating the fast load following ability while maintaining the safe operation, thus safe; efficient and fast load transition can be achieved. [ABSTRACT FROM AUTHOR]

• In this work we have successfully implemented two-step synthesis of redox-active PNIPAM-APMA nanogels grafted with 4-(3-carboxypropanamido)-TEMPO in mild aqueous conditions. • We suggested a universal approach to evaluate the "effective" concentration and diffusion coefficient of redox-active groups grafted to nanogel particles by eliminating the contribution from adsorbed layer of nanogels. • We provided evidence that electromigration of nanogels is significant even at high concentration of supporting electrolyte used in the electrochemical experiments. • Our work will promote further investigations in redox-active micro/nanogels electrochemistry and the role of their structure on the electrochemical properties, forwarding the basis for the rational design of redox-active gels for utilization as redox flow battery electrolytes. In this paper, we provide a thorough electrochemical study of redox-active nanosized cationic gels which are promising materials for redox flow battery electrolytes. We use two-step synthesis under mild aqueous conditions: precipitation polymerization of nanogels based on poly-(N-isporopylacrylamide- co -N-(3-aminopropyl)methacrylamide hydrochloride) (PNIPAM-co-APMA), and grafting of redox-active 4-(3-carboxypropanamido)-TEMPO units to the nanogels. We demonstrate stable reduction–oxidation behavior of such nanogels and suggest a universal approach to evaluate the "effective" concentration and diffusion coefficient of redox-active groups grafted to nanogel particles. For the TEMPO-grafted PNIPAM-co-APMA nanogels we find the "effective" concentration of TEMPO-groups to be approximately 50 % of their total concentration and demonstrate an increase of the "effective" concentration upon electrode rotation. Also, we investigate electron transfer kinetics of redox-active nanogels and provide an evidence that the adsorbed layer of nanogels facilitates electron transfer. [Display omitted] [ABSTRACT FROM AUTHOR]

• The synthesized ILs were used as novel green electrolytes for supercapacitors. • Among the ILs, the smallest anion, formate, exhibited the highest performance. • The highest value of energy density of 70 Wh kg−1 was related to the farmate anion. Supercapacitors are promising technologies for extremely effective energy storage and power management, which is a critical and major area of worldwide technological advancement. Ionic liquids (ILs) are an environmentally benign promising emerging class of versatile solvent systems. In this paper, for the first time, a new approach to the application of monoethanolamine-based ILs with anions formate, acetate, and propionate ([HEA]F, [HEA]A, and [HEA]P) as eco-friendly, affordable, and easy synthesis electrolytes are proposed for activated carbon (AC)-based supercapacitors. The ionic conductivity and the electrochemical stable potential window (ESPW) of ionic liquids were assessed. The electrochemical performance of synthesized ILs as an electrolyte in AC-based supercapacitors was compared. Electrochemical properties were performed by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), linear sweep voltammetry (LSV), and galvanostatic charge-discharge (GCD) methods to evaluate the electrolytic performance of ionic liquids in supercapacitors. The charge transfer resistance (R ct) and solution resistance (R s) decreased with decreasing anion size of ILs. At a scan rate of 10 mVs−1, the prepared supercapacitors using [HEA]F, [HEA]A, and [HEA]P ionic liquids deliver specific capacitance of 114, 95, and 73 F g−1, respectively. The maximum power density 2941 W kg−1 and maximum energy density 70 Wh kg−1 were obtained for the prepared supercapacitor using [HEA]F ionic liquid. The supercapacitors prepared with [HEA]F, [HEA]A and [HEA]P electrolytes show capacitance retention of 96%, 91% and 87% after 5000 charge-discharge cycles, respectively. [ABSTRACT FROM AUTHOR]

Iron-based aqueous batteries, such as the iron-air and nickel-iron chemistries, are limited by passivation and hydrogen evolution at the iron anode, especially at high current densities. In this paper, strategies to minimise these issues are investigated with iron electrodes composed of 20–50 nm Fe 2 O 3 nanoparticles produced by the Adams and Oxalate methods. The strategies include ball milling the Fe 2 O 3 with Ketjenblack carbon to improve conductivity, addition of bismuth sulphide to the electrode and 1-octanethiol to the electrolyte, and addition of potassium carbonate as a pore-forming agent. The ratio of Fe/C in the electrode and the 1-octanethiol additive have the greatest impact on the electrode capacity. The Fe/C ratio should be below 2.0 to ensure conductivity of the discharged electrode. The presence of 1-octanethiol can protect the electrodes from passivation during discharge; at very high 2C discharge rates adding 1-octanethiol increases the electrode specific capacity from 17 to 171 mAh/g Fe. The synthesis method and use of pore former do not have a significant effect on the capacity. In all electrodes, the Fe 2 O 3 nanoparticles are in the same crystalline phase after cycling and do not undergo significant crystal growth and passivation, demonstrating the stability and suitability of these materials for iron-based batteries. 3D image of experimental configuration (iron electrode versus a nickel counter electrode), with SEM image of electrode surface, and polarisation curves showing the discharge potential of the electrode in 6 mol dm−3 electrolyte with and without the presence of 0.1 mol dm−3 1-octanethiol additive. Image 1 • Effect of Fe/C ratio, synthesis method, and additives on Fe 2 O 3 electrodes. • The best ratio was Fe/C = 2.0, allowing a compact, dense electrode. • Synthesis methods gave capacities >900 mAhg−1 Fe higher than previously reported. • Electrodes showed none of the structural changes caused by passivation. • 1-octanethiol additive increased the capacity more than tenfold at the 2C rate. [ABSTRACT FROM AUTHOR]

This paper describes a hybrid capacitor based on identical activated carbon (AC) electrodes and the 1-ethyl-3-methylimidazolium selenocyanate, [EMIm][SeCN], liquid salt as redox-active electrolyte. [EMIm][SeCN] is a fluorine-free ionic liquid (IL) which combines good charge and mass transport properties (σ = 25 mS cm−1 and η = 17 mPa s−1), as well as redox activity originating from the pseudohalide anion. Owing to the impact of the SeCN−/(SeCN) 2 redox couple, the AC/AC capacitor based on this electrolyte displays remarkable discharge (from 1.5 V) capacitance of 49 and 56 F g−1 (expressed per total active mass of electrodes) using aluminum and stainless steel (SSt) current collectors, respectively. Although higher capacitance values were displayed for the hybrid capacitor with SSt components, more advantageous E 0 localization for cell hybridization was observed when using Al current collectors. [ABSTRACT FROM AUTHOR]

Abstract Lithium metal is considered one of the most promising anode materials for realizing high volumetric and gravimetric energy density, owing to the high specific capacity (∼3860 mAh g−1) and the low electrochemical potential of lithium (−3.04 V vs. the standard hydrogen electrode). However, undesirable dendritic lithium growth and corresponding instability of the solid electrolyte interphase prevent safe and long-term use of lithium metal anodes. This paper presents a simple electrolyte approach to enhance the performance of lithium metal batteries by tuning the dielectric constant of the liquid electrolyte. Electrolyte formulations are designed by changing the concentration of ethylene carbonate to have various dielectric constants. This study confirms that high ethylene carbonate content in a liquid electrolyte enhances the cycling performance of lithium metal batteries because the electric field intensity applied to the electrolyte is reduced in relation to the polarization of the electrolyte and thus allows smooth lithium plating and formation of a stable solid electrolyte interphase. We believe that this approach provides an important concept for electrolyte system design suitable to lithium metal batteries. Highlights • Electric field intensity for lithium plating is derived from interface analysis. • Electrolytes with different dielectric constants are designed systematically. • Confirmed enhanced cycling performance of lithium occurs with high EC content. [ABSTRACT FROM AUTHOR]

Abstract: The understanding of the very early stage of copper crystal formation kinetics and mechanism is very important for both fundamental and applied aspects. Particularly the quality of the industrial electrolytic copper deposit can be improved and better controlled. In this paper, copper nucleation mechanism is investigated in real refinery electrolytes. The main aim is to study the influence of potential, temperature and copper concentration on potentiostatic reduction of copper ions. The model of electrocrystallization is considered on the basis of the equations describing the nucleation controlled by diffusion towards a disc-shaped ultramicroelectrode. In the present paper the rates of copper nuclei formation are estimated under different applied potential, temperature, copper and levelling agent concentrations. [Copyright &y& Elsevier]

• An abnormal electrode behavior of graphite anode affected by the ES additive is found. • A dynamic evolution mechanism of SEI is proposed for explaining the capacity anomaly. • Graphite operating with the VC-ES electrolyte shows enhanced performance at 55 °C. Supplementing additives into the electrolyte is a simple and effective approach to improve the electrode performance of lithium-ion batteries (LIBs). Although vinylene carbonate (VC) and ethylene sulfite (ES) additives have been studied to improve the performance of LIBs with graphite anode, the abnormal electrode behavior of graphite anodes operating with the electrolyte containing VC and ES additives has never been reported. In this paper, we report on the discovery and interpretation of the room-temperature capacity anomaly of graphite anodes operating with the VC-ES electrolyte at relatively high C rates (≥ 0.5 C). A dynamic evolution mechanism of SEI is proposed on the basis of electrochemical analysis and surface examination of graphite anodes at different charge/discharge states. The merit of the VC-ES electrolyte over the VC electrolyte is found for graphite anodes operating at 55 ºC. The VC-ES electrolyte provided here holds great potential for application in LIBs with graphite anode operating at high temperatures. [Display omitted] The transformation of organic components to inorganic components in the solid electrolyte interface of graphite anodes results in capacity anomaly, when the current density is switched to and more than 0.5 C. [ABSTRACT FROM AUTHOR]

• The corrosion behavior of the Ni-based single crystal superalloy and its recast layer is investigated by electrochemical techniques in NaNO 3 solution. • The recast layer surface forms a stronger passivation film with high corrosion resistance. • Only γ phase exists in the recast layer, the surface bugle consists of oxide, and there is shedding during the electrochemical dissolution. • The γ phase on the surface of Ni-based single crystal superalloy is preferentially dissolved, leaving the block γ' phase. Ni-based single crystal superalloy is favored for turbine blades. In order to adapt to the high temperature of the working environment, film cooling technology is widely used. The film cooling holes of turbine blades require no recast layer residuals and high machining efficiency. Combined or hybrid methods of electrical discharge machining (EDM) and electrochemical machining (ECM) show prospective applications. Here, the recast layer generated by discharge during high-speed drilling is removed by electrochemical dissolution. But the dissolution behavior of it is not investigated. In this paper, The anodic electrochemical behavior of a Ni-based single crystal superalloy and its recast layer in NaNO 3 electrolyte is reported, and the surface morphology change of electrochemical dissolution is elucidated. The results showed that the γ' phase disappeared in the recast layer after EDM. Its oxide content within the passivation film is significantly elevated, exhibiting a stronger corrosion resistance than the matrix. For the material removal characteristics, the crater on the recast layer surface preferentially undergoes corrosion, adopting an alveolate structure, with the bulges later dissolved or removed by shedding due to oxide enrichment. For the matrix, the γ phase undergoes electrochemical dissolution, leaving a block γ' phase. A qualitative electrochemical dissolution model is established. [ABSTRACT FROM AUTHOR]

Plasma electrolytic oxidation (PEO) is normally not applicable to non-valve metals. However, in this study, PEO of Q345 carbon steel, a non-valve metal, has been carried out under pulsed unipolar regimes in aluminate based electrolytes with the addition of sodium dihydrogen phosphate to understand its coating formation and plasma generation mechanisms. Real time imaging, optical emission spectroscopy (OES), gas collection, scanning electron microscopy (SEM) assisted with energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) have been adopted to characterize the PEO processes. It has been found that the cell potential-time responses and plasma initiation are affected by the surface roughness of the carbon steel and the electrolyte agitation, which are not encountered in PEO of valve metals. The addition of sodium dihydrogen phosphate is critical to the establishment of stable plasma discharges and formation of thick PEO coatings on carbon steel. It has been found that the formation of a thin layer of aluminum phosphates (AlPO 4 and AlPO 4 ·2H 2 O) or alumina aluminum phosphate (AAP) at the initial PEO stage plays an important role for the plasma generation and hence PEO coating formation on carbon steel. The variations in the cell potential-time responses are associated with the stability of the aluminum phosphates or AAP layer on the carbon steel. The findings in this paper indicate that the presence of a dielectric layer on the metal surface is a prerequisite for the occurrence of plasma breakdown. Hence, the previous models that dielectric breakdown in PEO is preceded by the breakdown of a bubble layer need to be reconsidered. [ABSTRACT FROM AUTHOR]

For device fabrication, materials needs to satisfy 3Es (economical, environment friendly and easy to prepare) along with technical characteristics. Present paper reports an electrolyte synthesized by modifying potato starch by solution cast technique which is easy to synthesize, stretchable, bendable and twistable low cost (∼ INR 15/cm 2 ) free standing electrolyte film having wide electrochemical stability window (ESW ∼ 2.4 V), low equivalent series resistance (ESR ∼ 1.7 Ω) and small ion relaxation time (15 μs). Supercapacitors are fabricated using this electrolyte with two different electrodes (teflon coated carbon cloth and anodized aluminium). With laboratory prepared anodized Al as electrode, the electrochemical stability window is >4 V, ESR is <2 Ω and capacitance of ∼mF is obtained. Approximately −80° phase angle is obtained which remains constant from 1 Hz to 10 kHz range which covers the frequency requirement of ac line filtering application. The coulombic efficiency estimated from charging/discharging curves have values > 98% which approximately remains constant in studied number of cycle. All these indicate that prepared electrolyte is a potential candidate for electrochemical device applications. [ABSTRACT FROM AUTHOR]

This paper reports on the synthesis and characterization of novel dicationic ionic liquid electrolytes based on asymmetrical imidazolium-trialkylammonium ionic liquids. The results obtained indicate that the length of the alkyl chain attached to the nitrogen atom has a significant influence on the thermal and electrochemical properties of the electrolytes, as well as on parameters such as lithium ion coordination number and lithium ion transport number. All synthesized dicationic ionic liquids and the corresponding electrolytes are liquid at room temperature being thermally stable up to 300 °C; well above battery operation temperature. Room temperature ionic conductivities of the electrolytes are in the range of 0.8–7.2 × 10 −5  S cm −1 , with an electrochemical stability window of 1.5 V–5.0 V vs. Li/Li + . Synthesized electrolytes have been tested in Li half-cells using LiMn 2 O 4 (LMO) spinel as cathode material. Cyclic voltammetry, rate capability and galvanostatic cycling studies at 60 °C have been performed. Again, the alkyl chain length attached to the nitrogen atom plays a significantly role in the electrochemical performance of the LMO cells. Among the cells studied, the one assembled with the electrolyte 1M LITFSI doped IMI 1,6 -TEA exhibits the best rate capability and the high cycling performance. [ABSTRACT FROM AUTHOR]

Transition time in chronopotentiometry is an important parameter, which is widely used for electrochemical characterization of various systems. Occurrence of multiple transition times is typical for multicomponent or multilayer electrode and membrane systems. In this paper we show that there may be another cause of multiple transition times. It is electrical heterogeneity of ion exchange membrane surface. It is found that there are two transition times on the chronopotentiograms of a commercial anion-exchange MA-41 (Shchekinoazot) and two specially prepared cation-exchange heterogeneous membranes in dilute electrolyte solutions (0.02 M NaCl in the experiment). It is found that both transition times are determined by diffusion limitations of ion delivery to the membrane surface in the depleted diffusion layer. The value of the first transition time depends on the dimensions of the conductive regions and their surface fraction; this transition time is determined as the time necessary for the depletion of electrolyte concentration near the conductive regions of the surface. The rate of concentration depletion depends on the electromigration through the conductive regions, on the one hand, and on the normal the tangential ion diffusion to the conductive surface regions, which mitigate the concentration decrease, on the other hand. The experimental value of the first transition time for the laboratory-made membranes is in a good agreement with simulation using a 3D electrodiffusion model. The value of the second transition time is in a good agreement with the Sand theory, hence it is conditioned by the normal diffusion delivery of electrolyte from the solution bulk to the entire membrane surface. The tangential diffusion plays a secondary role in this stage of concentration polarization since current-induced convection levels off the concentrations along the heterogeneous membrane surface. [ABSTRACT FROM AUTHOR]

In this paper, we developed a very simple sol-gel spin-coating method to fabricate high performance CeTi x O y sensing membranes for a solid-state electrolyte-insulator-semiconductor (EIS) pH sensor. The surface morphologies, crystal structures, chemical compositions, and elemental depth profiles of the CeTi x O y membranes treated with three different titanium concentrations (0.1, 0.3 and 0.5 M) were studied using a combination of atomic force microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Auger electron spectroscopy, respectively. The structural properties of the CeTi x O y membranes were corrected with the sensing performances of CeTi x O y EIS pH sensors. The sol-gel synthesized CeTi x O y EIS device prepared at the 0.3 M condition exhibited the best sensing characteristics (pH sensitivity, hysteresis voltage and drift rate) among these conditions. We attribute this behavior to the optimal titanium content in the sensing membrane enhancing the surface roughness CeTi x O y film, increasing the Ce 3+ /Ce 4+ ratio, and forming the stoichiometric Ce 2 TiO 5 structure. [ABSTRACT FROM AUTHOR]

To make a Lithium Ion Battery (LIB) reliably rechargeable over many cycles, its graphite-based negative electrode requires the solid electrolyte interphase (SEI) as a protection layer. The SEI is formed through chemical and particularly electrochemical side reactions of electrolyte components in the first charging cycle(s) after manufacturing of a LIB. The SEI ideally serves two purposes: (i) act as a sieve permeable to Li ions but not to other electrolyte components and (ii) passivate the electrode against further electrolyte decomposition. Core element of conventional SEI formation is a lengthy, low-current galvanostatic charging step, which due to its time consumption contributes heavily to cell manufacturing costs. Here, we report on some non-conventional SEI formation protocols for composite carbon electrodes, inspired by recent experimental findings at smooth model electrodes. Acknowledging that the SEI forms in two main steps, taking place in a high-potential and a low-potential region, respectively, we demonstrate that less time spent in the high-potential region not only makes the process faster but even yields SEIs with superior kinetic properties. We tentatively explain this via basic rules of thin film growth and the role of grain boundaries for ion transport. We also report on the positive influence of multi-frequency potential modulations applied between high-potential and low-potential formation. Given that any new cell chemistry in principle requires its own tailor-made formation process, technologic success of future LIB cells will benefit from a systematic, well-understood toolbox of formation protocols. This paper is meant as a first step, highlighting potentially low-hanging fruits, but also flagging the demand for further systematic studies on model systems and on commercially manufactured cells. [ABSTRACT FROM AUTHOR]

La 0.4 Sr 0.6 TiO 3 (LST) nanofibers are prepared by electrospinning method, the LST nanofiber scaffolds are sintered on YSZ (8 mol% Y 2 O 3 -92 mol% ZrO 2 ) electrolyte flakes, and Gd 0.2 Ce 0.8 O 1.9 (GDC) and Ni infiltrate into La 0.4 Sr 0.6 TiO 3 nanofiber scaffolds. In this paper, the nanofiber-based LST-GDC-Ni composite anodes are tested in H 2 or CH 4 fuel gas, respectively, and show excellent thermal and redox cycling stability. Carbon deposition appears on the surface of nanofiber-based LST-GDC-Ni composite anodes after being fed with CH 4 fuel gas for 100 h. The amount of carbon deposition is proportional to the mass ratio of Ni:LST. A small amount of carbon deposition boosts the electrochemical performance, however, a large amount of carbon deposition is the opposite. The optimal mass ratio of LST:GDC:Ni has been found to be 1:1:0.4. [ABSTRACT FROM AUTHOR]

Symmetrical solid oxide fuel cells (SSOFCs) show many advantageous features of simplifying fabrication process, minimizing interdiffusion between components and enhancing coking and sulfur tolerance by operating the anode as the cathode. In this paper, the double-perovskite Sr 2 TiFe 0.9 Mo 0.1 O 6– δ (STFM01) and Sr 2 TiFe 0.8 Mo 0.2 O 6– δ (STFM02) oxides are synthesized by the traditional solid-state reaction and assessed as symmetrical electrodes. Both of the two materials show cubic double perovskite structure with outstanding structural stability, well chemical compatibility and matched thermal expansion coefficients with the common electrolytes in oxidizing and reducing atmospheres under SOFC operating temperatures. From the electrochemical performance, the electrolyte-supported single cell with STFM01 electrode presents the maximum power densities of 573 mW cm −2 in H 2 and 361 mW cm −2 in complex hydrocarbon fuels containing H 2 S at 850 °C, respectively. The electrochemical stability test exhibits that the STFM01 sample showed no any degradation in H 2 and acceptable degradation in hydrocarbon fuels, and STFM02 sample showed no any deterioration during 30-h test in hydrocarbon fuels, which implies that the STFM01 and STFM02 materials had remarkable ability of resisting carbon deposition and sulfur poisoning than the traditional anode material. The efficient and relatively stable double perovskite symmetrical electrodes are much more promising candidate materials for SSOFCs and are beneficial for realizing commercialization of SOFC. [ABSTRACT FROM AUTHOR]

Aqueous rechargeable batteries (ARBs) based on migration of two types of shuttle ions not only enrich the battery families but also make it more available for ARBs with operation potential higher than 1.2 V. In this paper, we report on electrochemical properties of ARBs in configuration of NaTi 2 (PO 4 ) 3 /C||LiMn 2 O 4 , i.e. NTP/C||LMO. NTP/C was prepared through a simple and scalable co-precipitation post annealing treatment method and featured with hierarchical structure, high specific surface area, and abundant mesopores. The electrochemical properties of individual anode and cathode were examined in 1 mol L −1 Li 2 SO 4 , 1 mol L −1 Na 2 SO 4 , and 0.5 mol L −1 Li 2 SO 4 /0.5 mol L −1 Na 2 SO 4 mixed electrolyte, respectively. It is found that NTP/C exhibits superior operation in 1 mol L −1 Na 2 SO 4 and inferior operation in 1 mol L −1 Li 2 SO 4 while the situation is contrary for LMO. However, NTP/C||LMO full cells with Li + /Na + -mixed electrolyte exhibit enhanced electrochemical performance, presenting an anode-dependant electrochemical behavior. When operating at 1C, NTP/C||LMO with Li + /Na + -mixed electrolyte can deliver a discharge specific capacity ( C dis ) of 104.6 mA h g −1 based on the weight of NTP/C, and a specific energy ( E cell ) of 59.5 W h kg −1 with corresponding specific power of 76.8 W kg −1 based on the total weight of active electrode materials. After 220 cycles at 1C, the C dis and E cell remain 75.7 mA h g −1 and 43.0 W h kg −1 , respectively. [ABSTRACT FROM AUTHOR]

The conventional enhancement in capacitive performance that only relies on electrode materials is limited. Here, based on the system-level design principle, we explore the possibility of enhancing capacitance through both electrode and electrolyte. A novel and ultrahigh-performance asymmetric supercapacitor has been fabricated using two redox electrode systems. The positive electrode system consists of graphene supported Co(OH) 2 nanosheet (Co(OH) 2 /GNS) electrode and mixed KOH and K 3 Fe(CN) 6 aqueous electrolyte. And the negative electrode system comprises carbon fiber paper supported activated carbon (AC/CFP) electrode in mixed KOH and p-phenylenediamine (PPD) aqueous electrolyte. The novel asymmetric supercapacitor exhibits a significantly improved capacitive performance (specific capacitance of 204.5 Fg −1 , operational voltage of 2.0 V) in comparison with that of the conventional asymmetric supercapacitor (66.8 Fg −1 , 1.5 V) fabricated without redox electrolyte. The improvement is attributed high reversibility and conductivity of electrode materials and redox electrolyte, as well as the synergistic effect between the two electrode systems, resulting in a ultrahigh energy density (114.5 Whkg −1 at a power density of 1000 Wkg −1 ), excellent power density (4000 Wkg −1 at an energy density of 31.6 Whkg −1 ) and long-term cycling stability (after 20000 cycles, initial capacitance remains well). These encouraging results afford a facile and efficient way to fabricate ultrahigh-performance supercapacitors for the increasing demands on the energy storage devices. [ABSTRACT FROM AUTHOR]

This paper describes the synthesis and properties of the porous MgO fibers used as a binder of the electrolyte for thermal batteries. Porous MgO fibers with controlled pore size were prepared by a facile hydrothermal method in the presence of polyethylene glycol (PEG). The effect of PEG addition on the pore sizes of the porous MgO fibers was systematically investigated. The influence of porous MgO fibers having different pore sizes on the electrolyte (LiCl-KCl) leakage and electrochemical performances of the corresponding model cells were measured. The results show that a large amount of PEG leads to porous MgO fibers having high specific surface area and total pore volume, and reaching the maximum, 13.65 m 2 g −1 and 0.097 m 3 g −1 respectively, at 1.5 mol% of PEG addition. The model cell fabricated with porous MgO fiber having high surface area and pore volume shows low deformation and electrolyte leakage, as well as high discharge capacity. Electrochemical impedance spectroscopy (EIS) analysis shows that, the ionic conductivity of the cell increases as the porous MgO fiber pore size increasing. These performances are much better than the performances of cell fabricated with traditional MgO powders. The dimensional stability and large surface area contact of porous MgO fibers with molten electrolyte should account for the superior physical and electrochemical performances of model cell fabricated with porous MgO fibers. [ABSTRACT FROM AUTHOR]

A novel multifunctional structural supercapacitor based on graphene and geopolymer infused with 2 M KOH electrolyte was fabricated. Metakaolin-based geopolymers, which were first applied as structural separators in this paper, were prepared with metakaolin and different moduli of alkaline activator solution. The widespread pores in geopolymer matrix provide enough channels for ion storage and motion. The effects of alkaline activator solution modulus and curing age on the electrochemical properties were analyzed. The results revealed the ideal capacitive behavior of structural supercapacitor. The samples with modulus of 2.0 exhibited the highest specific capacitance of 36.5 F g −1 at curing age of 28 days. A possible mechanism was proposed to explain the factors that influence the specific capacitance of geopolymer-based structural supercapacitor. The result of multifuncitonality analysis showed that samples with modulus of 1.6 exhibited the best level of multifunctionality, with compressive strength of 33.85 MPa and specific capacitance of 33.4 F g −1 at curing age of 28 days. It achieved a balance between mechanical property and electrochemical performance. [ABSTRACT FROM AUTHOR]

In this work, a two-dimensional mathematical model is developed to study the flow patterns and volumetric flow penetrations in a segment of flow channel over porous electrode layered system in vanadium flow battery with flow field design. The flow distributions at the interface between the flow channel and porous electrode are examined. It is found that the non-linear pressure distributions can distinguish the interface flow distributions under the ideal plug flow and ideal parabolic flow inlet boundary conditions. Nevertheless, the volumetric flow penetration within the porous electrode beneath the flow channel through the integration of interface flow velocity reveals that this value is identical under both ideal plug flow and ideal parabolic flow inlet boundary conditions. The volumetric flow penetrations under the advection effects by both flow channel and landing/rib are estimated. The maximum current density achieved in a flow battery with a flow field architecture can be predicted based on the 100% amount of electrolyte flow reactant consumption through the porous electrode beneath flow channel and landing/rib. The corresponding theoretical maximum current densities achieved in vanadium flow battery with one and three layers of SGL 10AA carbon paper electrode have reasonable agreement with experimental results under a proper permeability. [ABSTRACT FROM AUTHOR]

In the last two decades, tremendous work has been investigating the electro-reduction of metal oxide cathodes in what is known as the FFC-Cambridge process. This paper explores the electrolyte changes that occur during the electro-deoxidation of metal oxides. The investigation takes niobium oxide as a case study and subjects a Nb 2 O 5 cathode to a constant potential difference of 2.5V between the cathode and carbon anode during the in- situ recording of the cyclic voltammetry of the electrolyte on a glassy carbon electrode. The deoxidation of the cathode supplies oxygen ions that increase the oxygen content of the electrolyte, even in the very early stage of the process. We could detect many non-Faradic processes and increase the electrolyte electronic and ionic conductivity a few hours after starting the electro-deoxidation due to the reduction of CaO. It was also possible to detect partial dissolution of the cathode in the electrolyte and back deposition of Nb on the current collector. The dissolved niobium ions can combine with the oxide ion in the melt to form a negatively charged complex which can be discharged on the anode to form a thick ceramic layer. The electrolyte changes were also investigated using electrochemical impedance spectroscopy. [ABSTRACT FROM AUTHOR]

Hierarchical porous carbon material as a supercapacitor electrode material has attracted great attention from many researchers around the world. In this paper, a simple and efficient buried activation technique is introduced to prepare a high-specific-surface-area carbon foam (up to 3106.7 m 2 g −1 ), which possesses unique hierarchical porous structure composed of super-large macropores (0.5–5 μm), bicontinuous large micropores (1.14 nm) and small mesopores (3.12 nm). The hierarchical porous structure allows the rapid ion transport within the electrode, which endows the carbon foam with excellent supercapacitor performances in both 1 mol L −1 KOH and 1 mol L −1 H 2 SO 4 electrolytes. Very high specific capacitances of up to 364.2 F/g in KOH electrolyte and 413.6 F/g in H 2 SO 4 electrolyte at a current density of 1 A/g are demonstrated for the present carbon foam. Such the as-prepared electrode is able to deliver extremely high energy densities of 72.84 Wh/kg and 82.72 Wh/kg at a power density of 600 W/kg in KOH and H 2 SO 4 electrolytes, respectively. [ABSTRACT FROM AUTHOR]

Abstract This work shows relevant inconsistencies found in a paper recently published in Electrochim. Acta and how the conclusions are challenged by a more detailed textural characterization of a microporous carbon monolith. [ABSTRACT FROM AUTHOR]

This paper describes the effects of the length of the phosphonium alkyl chain in FSI-based ionic liquids (ILs) used as an electrolyte solvent with Si electrodes in a Li/Si half-cell. The electrochemical performance of Si nanoparticles at a high rate in the synthesized triethyl-n-butylphosphonium bis(fluorosulfonyl)imide) [P 2224 ][FSI] and triethyl-n-octylphosphonium bis(fluorosulfonyl)imide) [P 2228 ][FSI] ILs, which also contain 1 M LiFSI, is compared with that of a common organic electrolyte using either polyacrylic acid (PAA) or polyacrylonitrile (PAN) as a binder. For the three electrolytes, the highest performance was obtained with the PAN binder, while both electrodes in ILs exhibited superior performance compared to the conventional organic electrolyte. For the Si/PAN composite electrode, after 1000 cycles at 1 A.g−1, the delithiation capacities were 1344, 550 and 136 mAh.g−1 for [P 2224 ][FSI] in 1 M LiFSI, [P 2228 ][FSI] in 1 M LiFSI and the commercial organic electrolyte, which corresponded to capacity retentions of 61%, 50% and 5%, respectively. Our results indicate that the chemical structure of the phosphonium cation enabled the tuning of transport properties and significantly influences the electrochemical behavior of the Si anode in the presence of LiFSI/IL as an electrolyte. [Display omitted] [ABSTRACT FROM AUTHOR]

With the growing demand of safety and accurate control for electric vehicles, it is urgent to develop a physics-based electrochemical model of lithium-ion battery with simple calculation and high accuracy over wide temperature range for application in battery management system (BMS). However, traditional electrochemical models are too complex to be applied in real usage, and most of them fail to capture thermal characteristics of the cell. Therefore, a fractional-order model of lithium-ion battery considering polarization in electrolyte and thermal effect (FOMeT) is proposed in this paper. The fractional-order model (FOM) is improved by considering the polarization in electrolyte. The particle thermal model is proposed to describe the heat generation and absorption of the cell. Finally, the FOM considering electrolyte polarization and the particle thermal model are combined to form FOMeT by coupling the cell temperature and dynamics of lithium-ion. The results show that the proposed model performs high voltage accuracy and temperature accuracy over wide temperature range (273.15K∼318.15K) and wide current load range (0.5C∼2C). [ABSTRACT FROM AUTHOR]

• P-doped P-MoS 2 /Co x S y @C/CFP heterojunction electrocatalyst is firstly constructed. • The catalyst shows excellent HER performances both in alkaline and acidic mediums. • The optimized electronic structure of the catalyst is the intrinsic reason for the excellent HER performances. • DFT calculations confirms the decrease the d-band center and the rate-degerming step. It is still challenging for the development of highly efficient non-noble metal electrocatalysts toward hydrogen evolution reaction (HER). Herein, an unreported material constructing strategy of combining crystalline-amorphous hetero-interface and heteroatomic doping towards electrocatalytic HER is firstly presented. The authors fabricate a self-supported P-MoS 2 /Co x S y @C/CFP electrode consisting of P-doped crystalline-amorphous MoS 2 /Co x S y heterojunction in-situ grown on carbon fiber paper (CFP). Benefitting from the strong electronic interaction at the interface of crystalline MoS 2 and amorphous Co x S y , the electronic structure of MoS 2 /Co x S y @C/CFP is optimized. Moreover, the P doping can further optimize the electronic structure and enhance water adsorption of the catalyst and lower the kinetic energy barrier of HER. The heterojunction P-MoS 2 /Co x S y @C/CFP can not only exhibit excellent HER activity in alkaline electrolyte but also in acidic electrolyte, with the relatively lower overpotentials of 59 mV and 135 mV at the current density of 10 mA cm−2 in 1 M KOH and 0.5 M H 2 SO 4 ; 140 mV and 205 mV at the current density of 100 mA cm−2 in 1 M KOH and 0.5 M H 2 SO 4 , respectively, which the HER performance is among the best for non-precious metal-based electrocatalysts usable in both acidic and alkaline mediums. Theoretical calculations also confirm that the construction of crystalline-amorphous heterointerface between MoS 2 and Co x S y and P doping can effectively accelerate the electron transport and promote the HER reaction kinetics, thus enhancing the HER performance. This construction strategy for HER electrocatalyst provides a new avenue on electrocatalytic research. [Display omitted] A novel P-doped coral-like MoS 2 /Co x S y /C heterojuntion with abundant hetero-interfaces is successfully constructed, which exhibits excellent hydrogen evolution reaction (HER) performance both in alkaline and acidic mediums, with the relatively lower overpotentials of 59 mV and 135 mV at the current density of 10 mA cm−2 in 1 M KOH and 0.5 M H 2 SO 4 ; 140 mV and 205 mV at the current density of 100 mA cm−2 in 1 M KOH and 0.5 M H 2 SO 4 , respectively. The HER performance is among the best for non-precious metal-based electrocatalysts usable in both acidic and alkaline mediums. [ABSTRACT FROM AUTHOR]

Triphenyl phosphite (TPPi) was investigated as an electrolyte additive for high-voltage lithium-ion batteries using lithium-rich layered oxide cathode in this paper. The cyclic stability of Li 1.16 Ni 0.2 Co 0.1 Mn 0.54 O 2 was improved significantly with the adoption of 0.2 wt. % TPPi. The capacity retention of Li 1.16 Ni 0.2 Co 0.1 Mn 0.54 O 2 was improved significantly, especially at elevated temperature, from 69.0% to 89.6% after 90 cycles. Electrochemical and physical characterizations indicated that TPPi was oxidized at 4.2 V (vs. Li/Li + ), which was lower than that of the solvents and lithium extraction from Li 1.16 Ni 0.2 Co 0.1 Mn 0.54 O 2 , and the oxidization resulting in an artificial cathode interface film, which effectively inhibited the decomposition of traditional electrolyte and protected Li 1.16 Ni 0.2 Co 0.1 Mn 0.54 O 2 material from destruction. [ABSTRACT FROM AUTHOR]

This paper reports on the performance of the supercapacitor operating in aqueous acetic acid salts. Lithium, sodium and magnesium acetate aqueous solutions at various concentrations have been selected as electrolytes. Maximum operational voltage and the overall capacitor performance have been determined by several electrochemical techniques. Floating and galvanostatic charge/discharge tests proved the promising performance at high voltages (1.5 V); the capacitance values have been retained at more than 80% of initial value for all tested electrolytes. Additionally, due to the the ability to operate at high voltages, the maximum energy obtained in the system with 0.5 mol L −1 CH 3 COONa is more than two times higher than with 6 mol L −1 KOH, i.e., conventional aqueous capacitor. Taking into account a mild character of the electrolytes used, a novel concept of eco-friendly energy storage device has been proposed. [ABSTRACT FROM AUTHOR]

In this paper, the background, current research status and problems of separators for Li-ion batteries were reviewed first. Then a novel sandwich-like type of composite nonwoven separators was prepared to improve the performance of composite nonwoven Li-ion battery separators by combining SiO 2 /PVDF-HFP membranes with PVDF-HFP dipped PP nonwoven fabric. The physical and electrochemical properties of the composite separators were measured and analyzed. It is found that the mean pore size of the composite separators was in the range of 100 to 300 nm with maximum pore size less than 2 μm. The composite nonwoven-based separators possessed higher electrolyte uptake, stronger thermal stability, better wettability and lower interfacial resistance than the commercial PE separator. The batteries assembled with composite nonwoven separators showed stable cycling performance and improved rate performance. The composite nonwoven separators are expected to be a promising alternative to commercial PE separator. [ABSTRACT FROM AUTHOR]

Widespread commercialization of solid oxide fuel cells requires lowering its cost. It is generally accepted that to lower the cost of solid oxide fuel cells it is necessary to use metal alloys as interconnectors and, consequently, lower its operating temperature to slow down interconnectors degradation. As a result the area specific resistance of the cathodes should be lowered to sustain the performance of the cells. In order to slow the interconnectors degradation (due to corrosion and interdiffusion with the anode) and improve the performance of the cathodes, novel functional layers are introduced to the structure of the fuel cells. In this paper, results related to three kinds of functional layers will be presented: a thin cathode layer between the porous cathode layer and the electrolyte to improve the cathode performance, a buffer layer between the electrolyte and the cathode to slow down inter-diffusion of atoms and thin and dense interconnector coatings to slow down interconnectors degradation. The investigated layers are deposited by cost effective spin coating and spray pyrolysis methods. Introduction of the layers show positive and promising results. [ABSTRACT FROM AUTHOR]

Understanding the early stages of electrochemical nucleation and growth is the cornerstone for nanoscale electrodeposition. Although studied since decades, the process is not yet fully understood. In this paper, we introduce a new modelling approach to study the growth of a single hemispherical nucleus: Multi-Ion Transport and Reaction Model (MITReM). This approach takes into account the transport driven by diffusion and migration of all species in the electrolyte together with the electrochemical reactions at the electrode boundary. A Finite Element Method (FEM) is used to solve the balance equations for the concentration of all the active species and the electrolyte potential. In contrast to analytical models or discrete scale modelling techniques, the strength of this approach is that no assumptions on the diffusional or kinetic limitations have to be made. In addition, this novel platform allows to add further levels of complexity, such as multiple nuclei, adatom surface diffusion, aggregation, particle detachment, etc. The simulation results prove that, the initial growth stage of a 10 nm single hemispherical silver nucleus always starts under kinetic control, regardless of concentration and electrode potential. Later on, a transition from kinetic to diffusion control takes place. The time of transition depends on the imposed concentration and electrode potential. Moreover, the simulations clearly show that the growth rate is strongly affected by the imposed concentration and electrode potential, as it has been proven experimentally in countless occasions. Numerical simulation by MITReM proves to be of great interest to gain knowledge towards unravelling the early stages of electrochemical nucleation and growth processes. [ABSTRACT FROM AUTHOR]

The operating temperature of vanadium redox flow battery (VRFB) will change with seasons and places. Hence, the broad temperature adaptability of VRFB is one of the key issues which affect its large-scale practical application. In our previous work, we have reported the impact of temperature (−35 °C–50 °C) on the static stability, physicochemical and electrochemical properties of five typical vanadium electrolytes (Electrochim. Acta, 2016, 187, 525). As a follow-up study, VRFB single cells are evaluated in this paper at a broad temperature range under current density of 40–200 mA cm −2 . The results show that VRFB can operate from −20 °C to 50 °C with acceptable energy efficiency under appropriate current densities (e.g. 65%–78% at 100 mA cm −2 ). Ohmic and polarization resistances of VRFB decrease with temperature while the voltage efficiency and electrolyte utilization present the opposite tendency. The fast crossover of the vanadium ions at high temperatures aggravates the capacity fading of the cell. Notably, VRFB suffers much more damage during alternate temperatures operation between moderate temperature and high temperature, which should be given special attention. [ABSTRACT FROM AUTHOR]

A novel copolymer, poly(methyl methacrylate-acrylonitrile-butyl acrylate) [P(MMA-AN-BA)], was designed for high-safety and high voltage lithium ion battery in this paper. The copolymer was synthesized by emulsion polymerization, the corresponding membrane was prepared through phase inversion method and the gel polymer electrolytes (GPEs) were obtained by immersing the membranes into 1 M LiPF 6 liquid electrolyte. The performances of the copolymer, the membranes and its GPEs were characterized by Fourier transform infrared spectra, nuclear magnetic resonance spectra, scanning electron microscope, energy dispersive spectroscopy, Brunauer–Emmett–Teller, mechanical stability, differential scanning calorimetry, thermogravimetric analyzer, electrochemical impedance spectroscopy, cyclic voltammetry and charge/discharge test. The results show that the copolymer is obtained through opening the double bonds C C of its monomers. The mechanical strength and thermal stability of PE separator are promoted by coating the developed copolymer. The PE-supported and copolymer coated membranes exhibit homogeneous and interconnected pore structure, which helps to present the highest ionic conductivity of 1.70 × 10 −3 S cm −1 for the corresponding GPE at room temperature. The GPE is electrochemically stable up 5 V, and shows the acceptable cyclic and rate performance when used in LiNi 0.5 Mn 1.5 O 4 cathode. The high performance of GPE assures the practical application of high voltage cathode in lithium ion battery. [ABSTRACT FROM AUTHOR]

High-energy density Zinc-air batteries are currently of interest since they could play a key role in emerging large-scale energy storage applications. However, achieving good rechargeability of such metal-air batteries requires significant further research and development effort. Room Temperature Ionic liquids (RTILs) offer a number of ideal thermal and physical properties as potential electrolytes for large-scale energy storage applications and thus, can help increase the practicality of such electrochemical devices. This paper reports the synthesis and application of three novel quaternary alkoxy ammonium bis(trifluoromethylsulfonyl)amide based RTILs, with two or more ether functional groups designed to interact and solubilize zinc ions, in order to aid in the electrochemical reversibility of the metal. The anion is successfully reduced from, and re-oxidized into, the three alkoxy ammonium RTILs suggesting that they are potential candidates as electrolytes for use in zinc-air batteries. Cyclic voltammetry reveals that the presence of water reduces the activation barrier required to deposit zinc and assists stable charge/discharge cycling in an electrolyte consisting of 0.1 M Zn(NTf 2 ) 2 in the tri-alkoxy ammonium chain RTIL, [N 2(20201)(20201)(20201) ] [NTf 2 ], with 2.5 wt.% H 2 O. Further experiments demonstrate that with such electrolyte a Zn electrode can complete at least 750 cycles at a current density of 0.1 mA/cm 2 at room temperature. [ABSTRACT FROM AUTHOR]

The formation of anodic oxide films on the Ti6Al4V alloy in the NaTESi electrolyte has been studied in the present paper. An anodic film with a shallow pore-like texture was formed after anodizing to 10 V. Porous anodic films with increased porosity were generated after anodizing from 20 to 40 V, and the pores were developed mainly within the α phase. Significant amounts of sodium species were incorporated in the films, and the amount increased with increasing anodizing voltage. The current efficiency for the anodic film growth increased from 10 to 30 V, but decreased from 30 to 40 V due to the occurrence of more oxygen evolution. The film thicknesses determined by RBS were 15 nm, 65 nm, 115 nm and 250 nm at 10, 20, 30 and 40 V respectively. The film thickness generated at 10 V showed good agreement with the thickness of 11 nm revealed by transmission electron microscopy. The Raman spectra indicated that the degree of crystallinity of the anodic film increased at higher voltages. The dielectric permittivity of the film was estimated as ∼118 according to the results from transmission electron microscopy and electrochemical impedance spectroscopy. Single-lap shear bonding tests were employed to compare the strength of adhesively joined titanium alloy anodized to different voltages. The results revealed appreciable increase in bond strength with increasing anodic film thickness. [ABSTRACT FROM AUTHOR]

This paper is addressed on studying the electrolytes for electrical double layer capacitors with relatively high ionic conductivity and electrochemical stability for high energy density application. A systematic analysis of the electrochemical characteristics has been presented using spiro-(1,1′)-bipyrrolidinium tetrafluoroborate (SBP-BF 4 ) with 1.5 mol L −1 (M) in variety of solvent compositions including propylene carbonate (PC), ethylene carbonate (EC) and dimethyl carbonate (DMC), while the solvent mixtures are PC + DMC (1:1 in volume) and PC + DMC + EC (1:1:1 in volume). The physical properties and electrochemical performance of SBP-BF 4 -based electrolytes are improved by tuning solvent mixtures compositions for high working voltage application. The binary solvent system of PC + DMC electrolyte exhibits lowest viscosity of about 3.14 mPa s, while the ternary solvent system of PC + DMC + EC electrolyte exhibits highest conductivity of about 18.08 mS cm −1 . The SBP-BF 4 /PC-based electrolytes display excellent upper voltage hold capability about 3.5 V. The binary solvent system exhibits superior rate performance, when the charge cut-off voltage is lower than 3.2 V. The ternary solvent system exhibits superior rate performance than that of other two solvent systems electrolytes, when the charge cut-off voltage is higher than 3.2 V. The maximum energy density and power density of EDLCs using the ternary solvent system electrolyte are 41.5 Wh kg −1 and 17.0 kW kg −1 , respectively. The spiral cylindrical capacitors based on ternary solvent system electrolyte exhibits better cycle performance than that of other two solvent system electrolytes at the high working voltages. [ABSTRACT FROM AUTHOR]

From the literature overview, lithium difluorophosphate salt, LiPO 2 F 2 , is considered a powerful electrolyte additive capable of enhancing lithium-ion batteries' capacity retention. Lower cell impedance associated with SEI and/or CEI layers composition and texture modifications had been widely demonstrated, but without providing clear mechanisms. This paper sheds light on the reactivity of LiPO 2 F 2 by combining electrochemical measurements and analyzes of electrolyte degradation products at the interphases and in the electrolytes by means of infrared and mass spectrometry techniques. Fluorine substitution reaction by electrochemically formed anions leads to a mitigation of electrolyte solvents degradation and to the enrichment of the SEI layer with LiF and lithium organofluorophosphates. Furthermore, a discussion on the composition of the CEI layer that enables the prevention of the transition metals dissolution from positive electrode layered oxides materials is also presented. [ABSTRACT FROM AUTHOR]

The 4,5-dicyano-2-trifluoromethyl-imidazolide (TDI − ) anion is a potential lithium salt anion for lithium-ion batteries. In this paper the transport properties of LiTDI solutions in EC/DMC (50/50wt%) are compared to competing salts such as LiTFSI (lithium bis(trifluoromethylsulfonyl) imide), LiFAP (lithium tris(pentafluoroethane)-trifluorophosphate) and the most commonly used LiPF 6 (lithium hexafluorophosphate). LiTDI in EC/DMC exhibits the lowest viscosity among the investigated electrolytes, but also the lowest conductivity: 6.84 mS cm −1 at 25 °C (1 mol L −1 ). The self-diffusion coefficients ( D ( 7 Li ) and D ( 19 F )) determined by observing 7 Li and 19 F nuclei with the pulsed-gradient spin-echo (PGSE) NMR technique allowed access, through application of the Stokes-Einstein and Nernst-Einstein equations, to the lithium transference number ( t + ), the effective ionic radius and the ionic dissociation coefficient (α D ) of LiTDI in EC/DMC. The ion-pair dissociation and t + were also determined using conductivity and viscosity measurements and by following the Bruce-Vincent method respectively and were in good agreement with those obtained by PGSE-NMR. LiTDI displays in EC/DMC a cationic transference number t + = 0.58, which is higher than that of LiPF 6 in the same solvent mixture, meaning that the mobility of the PF 6 − anion is higher than the larger TDI − anion. Still, results from both methods indicate that, LiTDI, as many other lithium salts is only partially dissociated in EC/DMC. Only 31% of the ion pairs are dissociated at 25 °C whereas for LiPF 6 , LiTFSI and LiFAP this number reaches at least 64% in 1 mol L −1 solutions. [ABSTRACT FROM AUTHOR]