Effects of tetrabutylammonium hydrogen sulfate as an electrolyte additive on the electrochemical behavior of lead acid battery

Tetrabutyl ammonium hydrogen sulfate is an ion-paring reagent that has similar properties with ionic liquid. Ionic liquids belong to new branch of salts with unique properties that have ever increasing applications in electrochemical systems especially lithium-ion batteries. For the first time, the effects of tetrabutylammonium hydrogen sulfate (TBAHS) as an electrolyte additive in battery’s electrolyte was studied on the hydrogen and oxygen evolution overpotential and anodic layer formation on lead–antimony–tin grid alloy of lead acid battery by using cyclic voltammetry and linear sweep voltammetry in aqueous sulfuric acid solution. The grid surface morphology after cyclic redox reaction was studied by using scanning electron microscopy. The results show that, by increasing TBAHS concentration in the electrolyte, hydrogen and oxygen overpotential were increased, and so the crystalline structure of PbSO₄ layer changed. Also, cyclic voltammogram on carbon–PbO paste electrode shows that with presence of TBAHS in the electrolyte, oxidation and reduction peak current intensively increased and peak potential for oxidation and reduction of PbO were dependent on TBAHS concentration.     

Voltammetric and electrochemical impedimetric behavior of silica-based gel electrolyte for valve-regulated lead-acid battery

The gel electrolyte is an important component of the valve-regulated lead-acid (VRLA) batteries. In this study, fumed silica-based gel electrolyte systems were prepared. In this concept, several important parameters controlling the performance of the GEL-VRLA battery, such as the sulfuric acid and fumed silica concentrations, gel formulation, gelling time and rate, and different additives (Na₂SO₄ and MgSO₄), were scientifically investigated. The gel formulations were characterized by cyclic voltammetric and electrochemical impedance spectroscopic methods. The optimum parameters were determined by using the results of anodic peak currents and redox capacities, R _s and R _ct values. Addition of 6 % (w/w) fumed silica to 30 % (w/w) sulfuric acid, for preparation of gelled electrolyte, increased the battery performance significantly. According to the results of the transmission electron and optic microscope images of the gel electrolytes, the three-dimensional gel structure was prepared successfully. The optimization of sulfuric acid concentration and amount of Na₂SO₄ and MgSO₄ additives were examined for the first time in detail by cyclic voltammetry, electrochemical impedimetry, and battery test. Na₂SO₄ and MgSO₄ additives make a good combination with a gelled-electrolyte system and improve the charge/discharge capacity according to sulfuric acid electrolytes. According to the experimental results, the fumed silica-based gel electrolyte system has a great potential for application in gelled electrolyte VRLA batteries.     

Electrochemical properties of positive electrode in lead-acid battery modified by ammonium-based ionic liquids

The influence of selected types of ammonium ionic liquid (AIL) additives on corrosion and functional parameters of lead-acid battery positive electrode was examined. AILs with a bisulfate anion used in the experiments were classified as protic, aprotic, monomeric, and polymeric, based on the structure of their cation. Working electrodes consisted of a lead-calcium-tin alloy utilized in the industry for manufacturing current collectors of positive electrodes in lead-acid batteries (LABs). This alloy was used in the first part of the study for the evaluation of corrosion intensity and stability of electrolyte with AIL additives. In the second part, the grid made of the examined alloy was covered with positive active mass, the composition of which was modified by selected AIL. The selection of an appropriate substance was made based on parameters such as corrosion potential, corrosion current, polarization resistance, and hydrogen and oxygen evolution potentials. Techniques such as linear sweep voltammetry, corrosimetry, and electrochemical impedance spectroscopy were used. The conducted measurements revealed that polymeric AIL additive had an exceptionally positive influence on the inhibition of the corrosion process in LAB and electrochemical window of the electrolyte. The influence of this compound on the specific capacity and resistance of the active mass was also discussed.

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Effect of 1-octanethiol as an electrolyte additive on the performance of the iron-air battery electrodes

It has recently been established that 1-octanethiol in the electrolyte can allow iron electrodes to be discharged at higher rates. However, the effect of thiol additives on the air electrode has not yet been studied. The effect of solvated thiols on the surface positive electrode reaction is of prime importance if these are to be used in an iron-air battery. This work shows that the air-electrode catalyst is poisoned by the presence of octanethiol, with the oxygen reduction overpotential at the air electrode increasing with time of exposure to the solution and increased 1-octanethiol concentration in the range 0–0.1 mol dm⁻³. Post-mortem XPS analyses were performed over the used air electrodes suggesting the adsorption of sulphur species over the catalyst surface, reducing its performance. Therefore, although sulphur-based additives may be suitable for nickel-iron batteries, they are not recommended for iron-air batteries except in concentrations well below 10 × 10⁻³ mol dm⁻³.

Graphical abstract

     

Benzimidazolyl functionalized ionic liquids as an additive for high performance dye-sensitized solar cells

Benzimidazolyl functionalized ionic liquids were synthesized and applied as additives for dye-sensitized solar cells. The fabricated devices show an overall power conversion efficiency of ~7.79% under AM 1.5 radiation (50 mW cm(-2)), and an excellent long-term stability.     

Determination of an acidic scale in room temperature ionic liquids

The acidity scale of different Br?nsted acids in ionic liquids such as [BMIM][NTf2], [BMIM][BF4], and [BMMIM][BF4] has been investigated by determination of Hammett functions, using a spectrophotometric indicator method. This scale should permit one to correlate the acidity strength of ionic liquid systems with their ability to achieve acid-catalyzed reactions.     

Enhancement of Li-ion battery performance of graphite anode by sodium ion as an electrolyte additive

Electrochemical performance of a graphite electrode for lithium-ion batteries was successfully and easily improved by sodium ion dissolved in an electrolyte solution. Sodium ion was added by dissolving 0.22 mol dm⁻³ NaClO₄ into a 1 mol dm⁻³ LiClO₄ ethylene carbonate–diethyl carbonate (1:1 by volume) electrolyte solution prior to charge–discharge cycle. By sodium-ion addition, an irreversible capacity at the initial cycle was obviously reduced, and reversible discharge capacities increased with better capacity retention. From ac impedance measurements, a graphite electrode in the sodium ion added electrolyte had much smaller interface resistance compared to that obtained in sodium ion free one. Furthermore, the electrode surface morphology observed by electron microscopes after charge–discharge tests got more uniform in the sodium added electrolyte.     

细胞色素C在离子液体修饰电极上的电化学行为

分别合成了疏水和亲水性咪唑类离子液体,并制备了相应的两种离子液体修饰的玻碳电极。循环伏安法测量结果显示,细胞色素C在离子液体修饰的玻碳电极上的电子传递过程为一扩散控制的准可逆反应,表明咪唑类离子液体也可用作细胞色素C电子传递的有效促进剂。电化学交流阻抗谱的测量结果得到了与循环伏安相同的结论。     

Fabrication and characterization of supported dual acidic ionic liquids for polymer electrolyte membrane fuel cell applications

In this study, we proposed an innovative and versatile method for preparation of highly stable and conductive supported ionic liquid (IL) membranes for proton exchange fuel cell applications. Novel covalently supported dual acidic IL membranes were prepared by radiation induced grafting of 4-vinyl pyridine (4-VP) onto poly(ethylene-co-tetrafluoroethylene) (ETFE) film followed by post-functionalization via sequential treatments with 1,4-butane sultone and sulfuric acid to introduce pyridinium alkyl sulfonate/hydrogen sulfate moieties. The advantage of our approach lies in grafting polymers with highly reactive functional groups suitable for efficient post-sulfonation. The membranes displayed better swelling and mechanical properties compared to Nafion 112 despite having more than 3 times higher ion exchange capacity (IEC). The proton conductivity reached superior values to Nafion above 80 °C. Particularly, the membrane with ion exchange capacity of 3.41 displayed a proton conductivity of 259 mScm⁻¹ at 95 °C. This desired conductivity value is attributed to the high IEC of the membranes as well as dissociation of the hydrophobic ETFE polymer and hydrophilic pyridinium alkyl sulfonate groups. Such appealing properties make the supported IL membranes promising for proton exchange membrane fuel cells (PEMFC).     

Physical and electrochemical properties of low-viscosity phosphonium ionic liquids as potential electrolytes

A new group of room temperature ionic liquids based on triethylalkylphosphonium cations together with a bis(trifluoromethylsulfonyl)imide anion as a novel electrolyte is presented in this report. It was found that phosphonium ionic liquids showed lower viscosities and higher conductivities than those of the corresponding ammonium ionic liquids. Particularly, phosphonium ionic liquids containing a methoxy group, triethyl(methoxymethyl)phosphonium bis(trifluoromethylsulfonyl)imide and triethyl(2-methoxyethyl)phosphonium bis(trifluoromethylsulfonyl)imide, exhibited quite low viscosities (35 and 44 mPa s at 25 °C, respectively). Linear sweep voltammetry measured in neat phosphonium ionic liquids at a glassy carbon electrode indicated wide potential windows (at least −3.0 to +2.3 V vs. Fc/Fc⁺). Thermogravimetric analysis suggested that phosphonium ionic liquids were thermally stable up to nearly 400 °C, showing slower gravimetric decreases at high temperature compared to those of the corresponding ammonium ionic liquids.     

Effect of surfactant and mineral additive on the efficiency of lead-acid battery positive active material

The effect of Sodium tripolyphosphate (STPP) and mineral additive on the performance of the lead-acid battery positive plate has been investigated. The addition of alumina-silicate to the positive paste and STPP to the electrolyte modifies the shape and size of PbO₂ crystals and improves the utilization of the positive active material (PAM). The electrochemical performance of the positive active material was determined using galvanostatic discharge and electrochemical impedance spectroscopy (EIS). The crystal structure and morphology of the PAM (PbO₂) were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The water content of the PAM was calculated using Thermogravimetric analysis (TGA) technique. The results showed that the addition of surfactant and mineral additive changes the morphology and the crystallite size of the PAM. We observe a remarkable improvement of the discharge capacity of the PAM when the surfactant (STPP) is added in the electrolyte. The discharge capacity increases with the decrease of the crystallite size and the charge transfer resistance R_ct of the PAM. This shows that the addition of mineral additive and the surfactant together improves the electrical performance of lead-acid battery.     

Uranium halide complexes in ionic liquids: an electrochemical and structural study

The electrochemistry of the salts, [emim]2[UBr6] and [emim]2[UO2Br4] ([emim] = 1-ethyl-3-methylimidazolium), has been investigated in both a basic and an acidic bromoaluminate(III) ionic liquid. In the basic ionic liquid, the hexabromo salt undergoes a one-electron reversible reduction process at a stationary glassy carbon disc electrode, while the tetrabromodioxo salt was reduced to a uranium(IV) species by an irreversible two-electron process with the simultaneous transfer of oxide to the ionic liquid. On the other hand, dissolution of either of the salts in an acidic bromoaluminate(III) ionic liquid resulted in the formation of the same electroactive species. The solid state structures of the uranium chloride salts, [emim]2[UCl6] and [emim]2[UO2Cl4], have previously been reported, but have now been re-evaluated using a new statistical model developed in our group, to determine the presence or absence of weak hydrogen bonding interactions in the crystalline state.     

On the diffusion of ferrocenemethanol in room-temperature ionic liquids: an electrochemical study

The electrochemical behaviour of ferrocenemethanol (FcMeOH) has been studied in a range of room-temperature ionic liquids (RTILs) using cyclic voltammetry, chronoamperomery and scanning electrochemical microscopy (SECM). The diffusion coefficient of FcMeOH, measured using chronoamperometry, decreased with increasing RTIL viscosity. Analysis of the mass transport properties of the RTILs revealed that the Stokes-Einstein equation did not apply to our data. The "correlation length" was estimated from diffusion coefficient data and corresponded well to the average size of holes (voids) in the liquid, suggesting that a model in which the diffusing species jumps between holes in the liquid is appropriate in these liquids. Cyclic voltammetry at ultramicroelectrodes demonstrated that the ability to record steady-state voltammograms during ferrocenemethanol oxidation depended on the voltammetric scan rate, the electrode dimensions and the RTIL viscosity. Similarly, the ability to record steady-state SECM feedback approach curves depended on the RTIL viscosity, the SECM tip radius and the tip approach speed. Using 1.3 μm Pt SECM tips, steady-state SECM feedback approach curves were obtained in RTILs, provided that the tip approach speed was low enough to maintain steady-state diffusion at the SECM tip. In the case where tip-induced convection contributed significantly to the SECM tip current, this effect could be accounted for theoretically using mass transport equations that include diffusive and convective terms. Finally, the rate of heterogeneous electron transfer across the electrode/RTIL interface during ferrocenemethanol oxidation was estimated using SECM, and k(0) was at least 0.1 cm s(-1) in one of the least viscous RTILs studied.     

Effect of solidification temperature of lead alloy grids on the electrochemical behavior of lead-acid battery

One of the main electrochemical characteristics of a lead-acid battery is amount of water consumption. The effect of solidification temperature on electrochemical behavior (mainly hydrogen overvoltage) of Pb–Ca–Sn–Al (0.09%, Ca; 0.9%, Sn; 0.02%, Al) and Pb–Sb–Sn (1.7%, Sb; 0.24%, Sn) alloys, which are used in making the grid of lead-acid batteries, has been studied by cyclic voltammetry (CV) and linear sweep voltammety for different concentrations of sulfuric acid (ranging from 0.5 mol L^–1 to 4.0 mol L^–1). The morphology of the grid at some solidification temperatures was studied by optical microscopy. After one sweep of CV the surface of the electrode was investigated by using scanning electron microscopy.The results show that the potential of hydrogen evolution depends on the solidification temperature of the grids during production (mold temperature of grid casting). Also, at different solidification temperatures, different passivation phenomena, electrode surface constituents, and structure were observed.     

甘氨酸电解液添加剂对水系锌离子电池电化学性能的影响

水系锌离子电池因其高安全性、高容量、低价格等优点,有望成为下一代规模储能设备。然而,副反应、锌枝晶和有限的使用寿命阻碍了其实际应用。我们将电解质添加剂甘氨酸(Gly)引入到常规水系ZnSO₄电解质中。Gly中的极性基团(—COOH和—NH₂)可以调节Zn²⁺的溶剂化结构,从而重新分配Zn²⁺的沉积以避免枝晶和副反应发生。结果表明,在ZnSO₄电解质中添加50 mmol·L^-1的Gly后(ZnSO₄-Gly),Zn||Zn对称电池在1 mA·cm^-2和1 mAh·cm^-2下,表现出良好的循环寿命(3 000 h),明显高于使用ZnSO₄电解质的性能(300 h)。以ZnSO₄-Gly为电解液的Zn||MnO₂全电池,在比电容和倍率性能方面比无添加剂器件表现得更好。     

1,3-dialkylimidazolium-based room-temperature ionic liquids as background electrolyte and coating material in aqueous capillary electrophoresis

The 1-ethyl-3-methylimidazolium (EMIM) cation was found to have constant mobility of 4.5 x 10(-4) cm2 V(-1) s(-1) over the pH range of 3 to 11. The electroosmotic flow of bare silica capillary was reversed by the covalently bonded room-temperature ionic liquid (RTIL) coating. With run buffer of 5 mM EMIM (pH 8.5), NH4+ in human urine was separated from the K+ matrix and was detected to be 0.37 +/- 0.012%. K+, Na+, Li+, Ca2+, Mg2+ and Ba2+ were baseline separated in RTIL-coated capillary with run buffer of 10 mM EMIMOH-acetic acid at pH 5, and the concentration of the above ions in a red wine were detected to be 907, 27.9, 0, 71.0, 83.4 and 31.1 microg/ml, respectively. The RTIL-coated capillary showed stable electroosmotic flow for at least 80 h in the run buffer.     

The electrochemical stability of ionic liquids and deep eutectic solvents

Room temperature ionic liquids (ILs) composed of cations and anions, as well as deep eutectic solvents (DESs) composed of hydrogen bond donors (HBDs) and hydrogen bond acceptors (HBAs), are regarded as green solvents due to their low volatility. They have been used widely for electrochemically driven reactions because they exhibit high conductivity and excellent electrochemical stability. However, no systematic investigations on the electrochemical potential windows (EPWs), which could be used to characterize the electrochemical stability, have been reported. In this regard, the EPWs of 33 ILs and 23 DESs have been studied utilizing cyclic voltammetry (CV) method and the effects of structural factors (cations and anions of ILs, and HBDs and HBAs of DESs) and external factors (electrode, water content) on the EPWs have been comprehensively investigated. The electrochemical stability of selected ILs comprising five traditional cations, namely imidazolium, pyridinium, pyrrolidinium, piperidinium and ammonium and 13 kinds of versatile anions was studied. The results show that for ILs, both cation and anion play an important role on the reductive and oxidative potential limit. For a same IL at different working electrode, for example, glassy carbon (GC), gold (Au) and platinum (Pt) electrode, the largest potential window is almost observed on the GC working electrode. The investigations on the EPWs of choline chloride (ChCl), choline bromide (ChBr), choline iodide (ChI), and methyl urea based DESs show that the DES composed of ChCl and methyl urea has the largest potential window. This work may aid the selection of ILs or DESs for use as a direct electrolyte or a solvent in electrochemical applications.     

Determination of preservatives in soft drinks by capillary electrophoresis with ionic liquids as the electrolyte additives

A capillary electrophoresis method for separating preservatives with various ionic liquids as the electrolyte additives has been developed. The performances for separation of the preservatives using five ionic liquids with different anions and different substituted group numbers on imidazole ring were studied. After investigating the influence of the key parameters on the separation (the concentration of ionic liquids, pH, and the concentration of borax), it has been found that the separation efficiency could be improved obviously using the ionic liquids as the electrolyte additives and tested preservatives were baseline separated. The proposed capillary electrophoresis method exhibited favorable quantitative analysis property of the preservatives with good linearity (r² = 0.998), repeatability (relative standard deviations ≤ 3.3%) and high recovery (79.4–117.5%). Furthermore, this feasible and efficient capillary electrophoresis method was applied in detecting the preservatives in soft drinks, introducing a new way for assaying the preservatives in food products.     

Challenges with prediction of battery electrolyte electrochemical stability window and guiding the electrode – electrolyte stabilization

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Capillary zone electrophoresis of proteins applying ionic liquids for dynamic coating and as background electrolyte component

The use of ionic liquids in capillary electrophoresis, either as coating material or as components of the background electrolyte needs systematic standardization to set up optimal conditions. Excellent separation of the proteins was achieved using 1-ethyl-3-methylimidazolium tetrafluoroborate ([emim][BF₄]) or 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]) ionic liquids using the properly made ionic-liquid–water binary mixtures for the experiments. The binary mixture has a distinctly stable and well perceptible low pH, which depends on the concentration of the ionic liquid, and on the preparation time of the mixture. Optimal conditions for the electrophoretic separation were obtained upon a multivariate analysis of the experimental parameters (applied voltage, migration time, concentration, and type of the ionic liquid). The standardized condition provides a low electroendosmotic flow toward the anode, which, however, did not hinder the proteins to migrate toward the cathode. The migration of cytochrome c, lysozyme, myoglobin, trypsin, and apo-transferrin at a pH around 2, far below the isoelectric points of the proteins, showed RSD values of the migration times less than 7.5% and less than 6.5% when using [emim][BF₄] or [bmim][BF₄], respectively, either in run-to-run or day-to-day experiments. The determination of the extent of the EOF is not possible with the commonly used EOF markers, due to interaction with the ionic-liquid constituents. The interaction of the ionic liquids with the proteins influences the migration order in zone electrophoresis. This method has been applied successfully for the analyses of real biological samples such as proteins from egg whites and human tears.