Electrolyte Anions Research Articles

Influence of Electrolyte Composition on the Electrochemical Reaction Mechanism of Bismuth Fluoride Electrode in Fluoride Shuttle Battery

Fluoride shuttle battery (FSB) is a promising next-generation battery candidate. In the FSB, metal fluoride and organic solvent containing supporting electrolyte salt and anion acceptor were used a...

C2 and N3 substituted imidazolium functionalized poly(arylene ether ketone) anion exchange membrane for water electrolysis with improved chemical stability

The effect of substituents at C2 and N3 positions of imidazolium functional group on various properties of the poly(arylene ether) ketone based anion electrolyte membranes was studied. The synthesized membranes were applied for alkaline water electrolysis using zero gap designed cell in order to evaluate their cell performances. All of the membranes exhibited better ionic conductivity and electrochemical performance than the commercial Fumasep FAA-3 membrane. The C2 methyl and N3 butyl substituted imidazolium-based membrane (PAEK-APMBI) specifically showed quite high ionic conductivity of 0.0154 S cm−1 and the voltage of 2.53 V at the current density of 2 A cm−2 (in 10 wt% KOH solution) at 60 °C, while those of Fumasep FAA-3 membrane were 0.013 S cm−1 and 2.63 V, respectively. Especially, the PAEK-APMBI membrane exhibited the excellent alkaline stability with the 96% IEC retention after long-term treatment in alkaline environment, while the Fumasep FAA-3 membrane illustrated a significant reduction in IEC to 38%. Based on those results, the PAEK-APMBI membrane would be a promising candidate for application in anion exchange membrane electrolysis system.

Processes associated with ionic current rectification at a 2D-titanate nanosheet deposit on a microhole poly(ethylene terephthalate) substrate

Films of titanate nanosheets (approx. 1.8-nm layer thickness and 200-nm size) having a lamellar structure can form electrolyte-filled semi-permeable channels containing tetrabutylammonium cations. By evaporation of a colloidal solution, persistent deposits are readily formed with approx. 10-μm thickness on a 6-μm-thick poly(ethylene-terephthalate) (PET) substrate with a 20-μm diameter microhole. When immersed in aqueous solution, the titanate nanosheets exhibit a p.z.c. of − 37 mV, consistent with the formation of a cation conducting (semi-permeable) deposit. With a sufficiently low ionic strength in the aqueous electrolyte, ionic current rectification is observed (cationic diode behaviour). Currents can be dissected into (i) electrolyte cation transport, (ii) electrolyte anion transport and (iii) water heterolysis causing additional proton transport. For all types of electrolyte cations, a water heterolysis mechanism is observed. For Ca2+ and Mg2+ions, water heterolysis causes ion current blocking, presumably due to localised hydroxide-induced precipitation processes. Aqueous NBu4+ is shown to ‘invert’ the diode effect (from cationic to anionic diode). Potential for applications in desalination and/or ion sensing are discussed.

Drastically Reduced Ion Mobility in a Nanopore Due to Enhanced Pairing and Collisions between Dehydrated Ions.

Ion transport through nanopores is a process of fundamental significance in nature and in engineering practice. Over the past decade, it has been found that the ion conductivity in nanopores could be drastically enhanced, and different mechanisms have been proposed to explain this observation. To date, most reported studies have been carried out with relatively dilute electrolytes, while ion transport in nanopores under high electrolyte concentrations (>1 M) has been rarely explored. Through systematic experimental and atomistic simulation studies with NaCl solutions, here we show that at high electrolyte concentrations, ion mobility in small nanopores could be significantly reduced from the corresponding bulk value. Subsequent molecular dynamics studies indicate that in addition to the low mobility of surface-bound ions in the Stern layer, enhanced pairing and collisions between partially dehydrated ions of opposite charges also make important contributions to the reduced ion mobility. Furthermore, we show that the extent of mobility reduction depends on the association constant between cations and anions in different electrolytes with a more drastic reduction for a larger association constant.

The Effect of Chloride Anions on Charge Transfer in Dye-Sensitized Photoanodes for Water Splitting.

The photoelectrochemical behavior of dye-sensitized photoelectrochemical cells based on a TiO2 layer sensitized with ruthenium components, including an absorber, ruthenium(II)bis(2,2′-bipyridine)([2,2′-bipyridine]-4,4′-diylbis(phosphonic acid)) dibromide (RuP), and a catalyst, ruthenium(II) tris(4-methylpyridine)(4-(4-(2,6-bis((l1-oxidanyl)carbonyl)pyridin-4-yl)phenyl) pyridine-2,6-dicarboxylic acid) (RuOEC), was investigated in the following water-based electrolyte configurations: KCl (pH ≈ 5), HCl (pH ≈ 3), ethylphoshonic acid (pH ≈ 3) with a different KCl concentration, and a standard phosphate buffer (pH ≈ 7). The rate of charge transfer on the photoanode’s surface was found to increase in line with the increase in the concentration of chloride anions (Cl−) in the low pH electrolyte. This effect is discussed in the context of pH influence, ionic strength, and specific interaction, studied by cyclic voltammetry (CV) in dark conditions and upon illumination of the photoanodes. The correlations between photocurrent decay traces and CV studies were also observed.

Anion-immobilized polymer electrolyte achieved by cationic metal-organic framework filler for dendrite-free solid-state batteries

The practical application of solid-state batteries (SSBs) is restricted by the growth of lithium dendrites, which could be attributed to uneven Li deposition mainly caused by the barrier of free anions in solid polymer electrolytes (SPEs). Herein, a novel cationic metal-organic framework (CMOF) is proposed to immobilize anions and guide Li+ uniform distribution for constructing dendrite-free SSBs. The CMOF grafted with -NH2 group protects the ether oxygen of polymer chains by hydrogen bonds, which extends the electrochemical window to 4.97 V. Such CMOF tethers anions by electrostatic interaction of charge carriers and the specific surface area as high as 1082 m2 g−1 further strengthens the effect of anion absorption on the surface of CMOF, leading to a high Li+ transference number of 0.72. With the anion-immobilized composite electrolyte, the Li symmetrical cells can continuously operate for 400 h at 0.1 mA cm−2 and 200 h at 0.5 mA cm−2 without discernable dendrites, respectively. In addition, the SSBs constructed with LiFePO4 and LiFe0.15Mn0.85PO4 cathodes demonstrate excellent rate and cycle performances at 60 °C. These results indicate that anion immobilization by CMOF is a promising strategy to realize dendrite-free SSBs with high energy density and safety.

A comparative study of iron phthalocyanine electrocatalysts supported on different nanocarbons for oxygen reduction reaction

Developing non-platinum electrocatalyst with high performance and durability is strongly desired for the next-generation low-cost fuel cells. Here, we present a facile and scalable preparation method for the hybrid electrocatalysts of iron phthalocyanine (FePc) and seven different nanocarbons including carbon black (Vulcan and Ketjen black), carbon nanotubes, and mesoporous carbons. All the FePc/nanocarbon catalysts exhibited a higher activity for oxygen reduction reaction (ORR) than that of the commercial Pt/C, and the highest half-wave potential (0.918 V vs. RHE) ever reported in the literature was obtained from the composite catalyst of FePc and Ketjen black. Furthermore, the amount of electrochemically active sites (the centered iron ion of FePc) and turnover frequency of ORR on FePc were found to be respectively responsible for the electrocatalytic activities and long-term durability of the FePc/nanocarbon catalysts for ORR. We fabricated a MEA using FePc-KCB, anion electrolyte membrane and Pt/C as cathode, electrolyte membrane, and anode, respectively, and its power density in anionic medium reached 108 mW cm−2, which is higher than that of the conventional Pt/C catalyst. Such obtained results are important for the design of non-Pt based high efficient and durable ORR and fuel cell catalysts.

Anion-π interactions in lithium-organic redox flow batteries.

The anions in electrolytes are the carriers of lithium ions for lithium-organic redox flow batteries. Herein, we reported that the interactions between the electrolyte anions and electron-deficient redox-active organic molecules (anion-π interactions) have strong influences on the battery properties due to the anion-π-induced formation of radical anions or sandwich-like aggregates.

Voltammetric Study of Tin Electrodeposition on Polycrystalline Gold from Sulfuric and Methanesulfonic Acid

In this work, we have studied tin electrodeposition on polycrystalline gold electrodes from two different supporting electrolytes: sulfuric acid (SA) and methanesulfonic acid (MSA), both of them commonly used in the industry. This work aims to understand the effect of the different electrolyte anions on the deposition process. We show at least three different tin deposition mechanisms on gold: irreversible adsorption, underpotential deposition, and overpotential (bulk) deposition. Underpotential deposition leads to the formation of a layer of tin in SA and MSA with a coverage around ML (monolayer) and ML, respectively. The UPD Sn layer is however somewhat uncharacteristic as it is associated with island formation and surface alloying. Cyclic voltammograms in an extended potential range showed five distinct peaks: two cathodic peaks associated with tin underpotential and overpotential deposition, and three main anodic peaks, corresponding to the oxidation of the bulk Sn, of the AuSn intermetallic layer, and of the adsorbed Sn(II) to Sn(IV). Both voltammetric and rotating disk electrode measurements show that the kinetics of tin electrodeposition in MSA is slower than in SA, which we ascribe to Sn-MSA complex formation in solution. Slow Sn deposition in MSA promotes AuSn formation, in contrast to SA in which bulk tin deposition is more prominent. Complete Levich-type mass transport control of tin deposition in SA and MSA was only reached at low scan rate due to concurrent HER on the uncovered gold surface during the deposition process at higher scan rates. An unexpected surface-confined passivation process is observed in both electrolytes.

Столбиковые ниобиевые оксидные наноструктуры: механизм образования, микроструктура и электрофизические свойства

The morphology and microstructure of the columnar niobium oxide nanostructures were investigated. The dependences of their morphological sizes on the anodization voltages (100–450 V) and anodic alumina pore diameters (40–150 nm) were established. The features of ion transfer in the process of niobium local anodizing were investigated and the transport numbers of electrolyte anions and niobium cations were calculated. The formation and growth mechanism was proposed and discussed. The phase composition and electrophysical properties of the column nanostructures were investigated.

Anion and solvent dependency of the electronic coupling strength in mixed valent class II systems.

The influence of the coordination and ion pairing properties of electrolyte anions on electronic coupling in cationic class II mixed valent species was studied. In order to cover a range of electronic coupling strengths within the class II regime, weakly coupled 2,5-diferrocenyl-3,4-thiadiazol, moderately coupled 2,5-diferrocenyl thiophene and strongly coupled N-(4-dimethylaminophenyl)-2,5-diferrocenyl-1H-pyrrole were chosen as analytes. The electrochemical properties of these compounds were determined by cyclic and square wave voltammetry using electrolytes with varying ion pairing capabilities, such as [NBu4][Cl], [NBu4][PF6] and [NBu4][BArF] ([NBu4][B(C6F5)4]), as well as solvents with increasing dielectric constants (dichloromethane (εr = 8.93), acetone (εr = 20.56), acetonitrile (εr = 35.94) and propylene carbonate (εr = 64.92)). It is shown that the choice of electrolyte has a considerable impact on the electrostatic and the electron transfer features of the mixed valent compounds when solvents of low polarity and low relative permittivity such as dichloromethane are used. For the use of more polar solvents such as propylene carbonate the electrochemical and spectroscopic properties are almost electrolyte independent. The solvatochromic and ion-related changes in the spectroscopic properties are most pronounced for weakly coupled systems and decrease with an increase in the electron transfer coupling strength.

Ionic liquid based battery electrolytes using lithium and sodium pseudo-delocalized pyridinium anion salts.

The electrolyte salt plays an important role for the overall performance and safety of lithium- and sodium-ion batteries (LIBs and SIBs, respectively). Here, two new lithium and sodium pseudo-delocalized pyridinium anion based salts were used to prepare ionic liquid (IL) based electrolytes. The Li and Na salts of the 1-methylpyridinum 2,6-dicarboxylate anion (MM26py) were synthesized and dissolved in an IL matrix (Pyr14TFSI) - hence creating mixed anion electrolytes. The obtained electrolytes are stable up to 150 and 200 °C and show ion conductivities of 2.8 and 3.2 mS cm-1 at room temperature, for the LIB and SIB electrolytes, respectively. A competitive effect between the MM26py and the TFSI anions to coordinate the alkali metal cations is observed. Finally, the electrochemical stability windows of 2.3 and 2.5 V, respectively, confirm that these electrolytes can be used practically in medium-voltage LIBs and SIBs.

Electrochemical Formation of Self-Organized Nanotubular Oxide Layers on Niobium (Review)

Background: This mini-review paper is focused on the anodic formation of selforganized nanotubular oxide layers on niobium as a nontoxic and allergy-free metallic biomaterial. Objective: The main purpose of the work was to outline the research activities being undertaken on the electrochemical modification of niobium to obtain its porous oxide with enhanced biocompatibility. Method: The effect of various parameters, such as concentration of fluoride anions in electrolyte, pH of electrolyte, and current-voltage-time conditions on the anodic formation of Nb2O5 nanotubes, was summarized. Results: Thirty-seven references were included in this mini-review and they were divided into main five parts. First part outlined the electrochemical formation of self-organized nanotubular oxide layers on niobium via anodic oxidation. The mechanism of the electrochemical formation of niobium oxide nanotubes was discussed. Second part presented the influence of the electrolyte type used for anodic oxidation of niobium and the fluoride ion concentration in the electrolyte on the type and dimensions of the obtained oxide niobium nanotubes. The influence of the applied voltage during anodic oxidation of niobium on the morphological parameters of the formed nanotube arrays was described in third part. The importance of the selection of the electrolyte pH for tailoring the length of niobium oxide nanotubes was demonstrated in fourth part. The last part outlined the structure of niobium oxide nanotubes. Conclusion: Key results were extracted and reviewed from publications of research activity in anodic oxidation of niobium introduced basics of that process and the current trends in electrochemical improvement of biocompatibility of metallic nanobiomaterials were presented. Keywords: Anodic oxide, anodization, electrochemical modification, nanotubes, niobium, oxide layers.

The Effect of Electrolyte Anion Composition on the Corrosion Behavior of Cadmium, Bismuth, and Their Eutectic Alloy in Borate Buffers

The effect of borate anion concentration on the electrochemical corrosion behavior of Cd–Bi eutectic alloy in borate buffers with a pH of 7.4 is studied. The results for the alloy are contrasted with the data obtained for the individual metals. Borate species are shown to participate in the anodic dissolution of the three systems in question. We identified similarities in dissolution behaviors of the alloy and its electronegative component (cadmium).

Safe, economical and fast-charging secondary batteries using single-walled carbon nanotubes

We developed a new concept aqueous electrolyte secondary battery by combining redox reactions of iodide ions in single-walled carbon nanotubes (SWCNTs) and alkali metal ions with quinone molecules. The new concept battery consisting only of abundant elements utilizes the fast ion movements of both the cation and anion in a safe aqueous electrolyte medium. As active quinone molecules, anthraquinone (AQ) and 9,10-phenanthrene quinone (PhQ) were used. AQ and PhQ molecules were inserted in SWCNTs because the electric conductivities of AQ and PhQ molecules are insufficient as battery electrode materials. Both redox reactions of the cation and anion of an alkali metal halide aqueous electrolyte were investigated by electrochemical measurements such as cyclic voltammetry and chronopotentiometry. The redox reaction of iodide ion was observed by chronopotentiometry as a very flat charge/discharge potential plateau at about 0.45 V vs. Ag/AgCl. On the other hand, PhQ redox reactions showed gradient potential plateau. It was also found that the discharge plateau potential of PhQ electrode measured with NaI aqueous electrolyte is about 0.1 V lower than that with LiI.

Hybrid Organic–Inorganic Functionalized Dodecaboranes and Their Potential Role in Lithium and Magnesium Ion Batteries

Currently, development of rechargeable Mg ion batteries is an important and hot topic of research. For its development, the major challenge is to find suitable stable electrolyte anions, which possess solubility in low-polarity solvents. In this context, new organic and hybrid organic–inorganic functional derivatives of closo dodecaborane dianion, namely B12X122– (X = −C≡CH, −C≡C–CN, and −C≡C–BO), are proposed here using density functional theory. The second excess electron in B12(C≡C–CN)122– and B12(C≡C–BO)122– is very strongly bound with the ΔE2 value of 4.90 and 5.14 eV, respectively, in the gas phase, which is almost six-times higher than that of B12H122– (0.81 eV). The various other factors responsible for the high stability of these predicted dianions have been explained in detail. We have explored the implications of these stable dianions as electrolytes in the Li and Mg ion batteries, and the results are found to be highly promising. Among all the dianions considered here, B12(C≡C–BO)122– and B12(C≡C–CN)122– are the most suitable choices as the electrolyte of the Li and Mg ion batteries, as the Li+/Mg2+ salt of these two dianion requires very less energy to dissociate into corresponding cation and anion. In addition, the oxidation potential of B12(C≡C–BO)122– and B12(C≡C–CN)122– dianions versus Mg2+/Mg is very high (12.91 and 12.58 V, respectively). Present work reveals that it is possible to design desired multiply charged stable anions for appropriate applications through suitable organic–inorganic functionalization.

CHLORIDE CONCENTRATION, NOT SODIUM AND POTASSIUM, IS SELECTIVELY HIGHER IN HEART FAILURE-ASSOCIATED PLEURAL EFFUSION

SESSION TITLE: Pleural Disease SESSION TYPE: Original Investigations PRESENTED ON: 10/07/2018 02:15 pm - 03:15 pm PURPOSE: My recent studies have shown that serum chloride is a key electrolyte for the regulation of the fluid distribution or shift between the intravascular and cellular (red blood cell) spaces in the heart failure (HF) pathophysiology. Electrolyte chloride may have an important role for accumulation of pleural fluid in acutely worsening HF. The present study evaluated the hypothesis that a differential chloride concentration exists between the pleural fluid and blood serum in patients with worsening HF. METHODS: Seventeen consecutive patients that presented to Nishida hospital with pleural effusion and underwent thoracentesis during the study period from May 2017 to December 2017 were retrospectively analyzed. Worsening HF was diagnosed based on clinical criteria (presentation, echocardiography, serum b-type natriuretic peptide, and response to therapy). Biochemical measurements were performed on samples of non-heparinized pleural fluid and peripheral venous blood obtained within 2 h from each other. Pleural effusion was classified as transudates or exudates according to the classic Light’s criteria. Namely, the effusion was classified as exudates when any of the following criteria were met: 1) pleural to serum protein ratio >0.5, 2) pleural fluid LDH >200 IU, and 3) pleural fluid-to-serum LDH ratio >0.6. The effusion-serum electrolyte gradient was determined as [(pleural fluid electrolyte) minus (serum electrolyte)]. Statistical analysis was performed by one-way analysis of variance with Tukey’s post-hoc test. RESULTS: Fifteen patients (53% men; 85±11 years) were diagnosed with HF-associated pleural effusion; based on the Light’s criteria, 10 of these patients were classified as having transudative effusion and the other 5 patients were classified as having exudative effusion [fulfilling only one (n=4) or both (n=1) of the LDH criteria]. The effusion-serum electrolyte gradient was significantly higher in chloride (7.4 ± 2.6 mEq/L; range 4 – 14 mEq/L) than in sodium (0.87 ± 1.36 mEq/L; range -1 – 4 mEq/L) and potassium (-0.12 ± 0.254 mEq/L; range -0.8 – 0.2 mEq/L; P < 0.001 for each). CONCLUSIONS: In acutely worsening HF patients with associated pleural effusion, concentration of chloride in the pleural effusion is greater than that in the serum, indicating that chloride may have an important and active role in the formation and retention of body fluid in the pleural space, and possibly in the interstitial space. CLINICAL IMPLICATIONS: The finding of higher chloride concentration in HF-associated pleural fluid as shown in this study should raise innovative idea for investigating the pleural fluid pathophysiology. According to the “revised Starling equation and the glycocalyx model”, anionic electrolyte chloride may penetrate the endothelial glycocalyx layer, diffuse into the pleural space, and hold pleural fluid by its tonicity under condition of insufficient drainage via venous and/or lymphatic channels. DISCLOSURES: No relevant relationships by Hajime Kataoka, source=Web Response

Enhancement of rapid charging capability of organic radical battery using ethylene carbonate-based electrolyte containing LiFSI

In poly(2,2,6,6-tetramethylpiperidinyl-N-oxyl-4-yl methacrylate) (PTMA) gel with lithium bis(fluorosulfonyl)imide (LiFSI), the salt concentration dependence on the ionic conductivity and the viscosity indicates that LiFSI has a high degree of dissociation and weak interaction with the PTMA. These properties retain fast charge transportation even at a high salt concentration in the gel. When salt concentration is increased to 1.5 mol/L, the diffusion coefficient for the gel containing LiFSI is almost unchanged. The capacity at 120C charging in organic radical battery (ORB) is increased by 20 mAh/g as LiFSI concentration increases from 1.0 to 1.5 mol/L. These results suggest that the increase in LiFSI concentration suppresses the shortage of electrolyte anions, which is involved in the oxidation reaction of nitroxyl radicals, at high rate charging. The ORB with 1.5 mol/L LiFSI-ethylene carbonate/dimethyl carbonate (4:6, v/v) is charged to 80% capacity in 30 s by using a 120C-constant current/constant voltage charge.

Dendrite-Free Epitaxial Growth of Lithium Metal during Charging in Li-O2 Batteries.

Lithium (Li) dendrite formation is one of the major hurdles limiting the development of Li-metal batteries, including Li-O2 batteries. Herein, we report the first observation of the dendrite-free epitaxial growth of a Li metal up to 10-μm thick during charging (plating) in the LiBr-LiNO3 dual anion electrolyte under O2 atmosphere. This phenomenon is due to the formation of an ultrathin and homogeneous Li2 O-rich solid-electrolyte interphase (SEI) layer in the preceding discharge (stripping) process, where the corrosive nature of Br- seems to give rise to remove the original incompact passivation layer and NO3- oxidizes (passivates) the freshly formed Li surface to prevent further reactions with the electrolyte. Such reactions keep the SEI thin (<100 nm) and facilitates the electropolishing effect and gets ready for the epitaxial electroplating of Li in the following charge process.

Dendrite‐Free Epitaxial Growth of Lithium Metal during Charging in Li–O2 Batteries

AbstractLithium (Li) dendrite formation is one of the major hurdles limiting the development of Li‐metal batteries, including Li‐O2 batteries. Herein, we report the first observation of the dendrite‐free epitaxial growth of a Li metal up to 10‐μm thick during charging (plating) in the LiBr‐LiNO3 dual anion electrolyte under O2 atmosphere. This phenomenon is due to the formation of an ultrathin and homogeneous Li2O‐rich solid‐electrolyte interphase (SEI) layer in the preceding discharge (stripping) process, where the corrosive nature of Br− seems to give rise to remove the original incompact passivation layer and NO3− oxidizes (passivates) the freshly formed Li surface to prevent further reactions with the electrolyte. Such reactions keep the SEI thin (&lt;100 nm) and facilitates the electropolishing effect and gets ready for the epitaxial electroplating of Li in the following charge process.