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.     

Ionic studies of sodium alginate isolated from Sargassum terrarium (brown algea) karachi coast with 2,1-electrolyte

Physical and chemical analysis of the polysaccharide isolated from Sargassum Terarrium (brown algae) of Karachi coast showed characteristics of the sodium alginate. Optical rotations and sulphated ash content were found and FTIR spectra showed a sharp and strong absorption band at 1600 cm^?1 representing carboxylate ion which conforms high uronic acid content of the product. The viscosities of aqueous 0.1% sodium alginate solution were measured in the presence of copper II chloride (CuCl₂). The viscosities were found to be increased with the increase in the concentration of electrolyte. Viscosities were also found affected with temperature. ‘A’ and ‘B’ coefficients of Jones–Dole equation were evaluated. The increase in positive values of ‘B’ coefficient with the rise of temperature led to conclusion that given electrolyte in 0.1% aqueous sodium alginate solution behaves as structure maker. Thermodynamic parameters regarding to activated state like energy of activation E_η, change in free energy of activation ΔG_η and change of entropy of activation ΔS_η were also evaluated. Straight-line plots of log η versus 1/T observed with positive slopes show the effect of temperature on the viscosities of solutions. Energy of activation (E_η) was found to be decreased with the rise of temperature. Change in free energy of activation (ΔG_η) was also found to be increased with increase in concentrations of electrolyte and also with rise of temperature. The values of change in entropy of activation (ΔS_η) were also calculated. Negative values of ΔS_η were found to be increased with increase in concentration of electrolyte and also with rise of temperature.     

Conductance study of the thermodynamics of micellization of 1-hexadecylpyridinium bromide in mixed solvents containing dilute electrolyte solutions

The critical micelle concentration (CMC) of hexadecylpyridinium bromide (HDPB) is determined conductometrically in binary mixtures of water + cosolvent at various temperatures and at low concentrations of sodium bromide, ranging from 0 to 2.4 × 10^?2 M. Dimethylsulfoxide (DMSO) and acetonitrile (AN) were used as cosolvents added to water. The ability of NaBr to lower the CMC of HDPB in water is inhibited by DMSO and AN. Thermodynamic parameters of micellization ΔH_m ^o, ΔS_m ^o, and ΔG_m ^o are evaluated according to the pseudo-phase model. The contribution of DMSO and AN in the micellization process of HDPB in aqueous electrolyte solutions are discussed in terms of the observed thermodynamic properties.     

Synergistic effect of fluorinated solvent and Mg2+ enabling 4.6 V LiCoO2 performances

Increasing the charging cut-off potential of lithium cobalt oxide (LiCoO₂, LCO) can effectively improve the energy density of the lithium-ion batteries, which are the mainstream energy storage devices used in 3C electronic products. However, the continuous decomposition of the electrolyte and dissolution of Co from the electrode will occur at high-potential operation, which deteriorate the performances of LCO. Here, a cathode-electrolyte interface (CEI) layer containing MgF₂ is constructed to enhance the electrochemical stability of LCO at 4.6 V (vs. Li⁺/Li). The Mg²⁺ added to the cathode gradually releases into the electrolyte during cycling, which forms a stable MgF₂-rich protective layer. In addition, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropylether (TTE) is added to the electrolyte acting as a F source to increase the content of MgF₂ in the CEI layer. The MgF₂-rich CEI layer effectively suppresses the decomposition of electrolyte components and the dissolution of Co of LCO, which makes the Li||LiCoO₂ (Li||LCO) cell cycled stably at 3∼4.6 V (vs. Li⁺/Li) in 200 cycles with a retention of 83.9%.     

Polarographic determination of acids by means of the reduction wave of quinones in methyl cellosolve solution

Methyl-p-benzoquinone (MQ) gives a single polarographic wave in methyl cellosolve media containing perchlorate as supporting electrolyte, but a prewave corresponding to the reaction Q + 2HA + 2e ái H₂Q + 2A^-, is found when an acid is added. The height of the prewave is proportional to the concentration of added acid. Traces (ca. 0.2%) of free perchloric acid can be determined in crude lithium perchlorate.The half-wave potential of the prewave depends on the pK_a value of the acid; if the dissociation constants of acids differ sufficiently, two prewaves are found and each acid species can be determined simultaneously. This method was applied to the MQ-HClO₄-CH₃COOH, MQ-CCl₃COOH-CH₃COOH and MQ-CHCl₂COOH- CH₃COOH systems.     

Thermochemistry of copper(II) ion solvation in aqueous organic solvents

The integral heat effects of CuCl₂ dissolution in aqueous DMSO, aqueous ethanol and aqueous acetone solutions at 298. 15 K in the electrolyte concentration range 0.001–0.01M were measured by means of calorimetry. ΔH _sol ⁰ values were obtained by extrapolation to zero electrolyte concentration. Literature data were used to determine the thermodynamic characteristics of Cu²⁺ transfer from water to aqueous organic solvents.     

Wetting films on a hydrophilic silica surface obtained from aqueous solutions of hydrophobically modified inulin polymeric surfactant

The thickness of wetting films on a hydrophilic silica surface was investigated using a microinterferometric technique. Aqueous solutions of hydrophobically modified inulin (INUTEC^®SP1) at various concentrations, in the presence or absence of NaCl or Na₂SO₄, were studied. The equilibrium film thickness (h _eq) showed a complex dependence on INUTEC^®SP1 concentration. At low electrolyte concentrations, h _eq decreased with an increase in INUTEC^®SP1 concentration, reaching a minimum at 10^?6 mol dm^?3. However, at high electrolyte concentrations, this dependence became less pronounced. At any given INUTEC^®SP1 concentration, the equilibrium film thickness decreased with an increase in electrolyte concentration as a result of the compression of the electrical double layer reaching a minimum value. After that, the film thickness showed a small decrease with further increase in electrolyte concentration. This indicates that the electrostatic component of disjoining pressure can be neglected, and the steric repulsion of the loops and tails of INUTEC^®SP1 determined the film thickness.     

Degradation of azithromycin using Ti/RuO<Subscript>2</Subscript> anode as catalyst followed by DPV,HPLC–UV and MS analysis

The electrodegradation of azithromycin was studied by its indirect oxidation using dimensionally stable Ti/RuO₂ anode as catalyst in the electrolyte containing methanol, 0.05 M NaHCO₃, sodium chloride and deionized water. The optimal conditions for galvanostatic electrodegradation for the azithromycin concentration of 0.472 mg cm^?3 were found to be NaCl concentration of 7 mg cm^?3 and the applied current of 300 mA. The differential pulse voltammetry using glassy carbon electrode was performed for the first time in the above-mentioned content of electrolyte for the nine concentration of azithromycin (0.075–0.675 mg cm^?3) giving the limits of azithromycin detection and of quantification as: LOD 0.044 mg cm^?3 and LOQ 0.145 mg cm^?3. The calibration curve was constructed enabling the electrolyte analysis during its electrodegradation process. The electrolyte was analyzed by high-performance liquid chromatography and electrospray ionization time-of-flight mass spectrometry. The electrooxidation products were identified and after 180 min there was no azithromycin in the electrolyte while TOC analysis showed that 79% of azithromycin was mineralized. The proposed degradation scheme is presented.     

Raman spectroscopic determination of oxoanions in aqueous polysulfide electrolyte solutions

The equilibrium distribution of aqueous sodium polysulfide solutions is investigated over a wide concentration range using Raman spectroscopy technique. A total of eighteen bands were determined in the spectra recorded for aqueous electrolyte solutions of different S:Na ratios. Beyond the presence of four polysulfide (S_n²⁻) species, where “n” varied between 2 and 5 as reported in previous literature, the originality of this study is to show the presence of oxidised sulfur species in these aqueous polysulfide solutions. A detailed comparison of all the bands for polysulfide and oxoanion species determined in this study with those cited in literature is summarised.     

High-performance all-solid-state electrolyte for sodium batteries enabled by the interaction between the anion in salt and Na3SbS4

All-solid-state sodium batteries with poly(ethylene oxide) (PEO)-based electrolytes have shown great promise for large-scale energy storage applications. However, the reported PEO-based electrolytes still suffer from a low Na⁺ transference number and poor ionic conductivity, which mainly result from the simultaneous migration of Na⁺ and anions, the high crystallinity of PEO, and the low concentration of free Na⁺. Here, we report a high-performance PEO-based all-solid-state electrolyte for sodium batteries by introducing Na₃SbS₄ to interact with the TFSI⁻ anion in the salt and decrease the crystallinity of PEO. The optimal PEO/NaTFSI/Na₃SbS₄ electrolyte exhibits a remarkably enhanced Na⁺ transference number (0.49) and a high ionic conductivity of 1.33 × 10⁻⁴ S cm⁻¹ at 45 °C. Moreover, we found that the electrolyte can largely alleviate Na⁺ depletion near the electrode surface in symmetric cells and, thus, contributes to stable and dendrite-free Na plating/stripping for 500 h. Furthermore, all-solid-state Na batteries with a 3,4,9,10-perylenetetracarboxylic dianhydride cathode exhibit a high capacity retention of 84% after 200 cycles and superior rate performance (up to 10C). Our work develops an effective way to realize a high-performance all-solid-state electrolyte for sodium batteries.

A high-performance all-solid-state PEO/NaTFSI/Na₃SbS₄ electrolyte for sodium batteries is realized owing to the electrostatic interaction between TFSI⁻ in the salt and Na₃SbS₄, which immobilizes TFSI⁻ anions and promotes the dissociation of NaTFSI.     

Concentration dependent spectral changes of electrons trapped in MgCl2 and CaCl2 glasses. A pulse radiolysis study

The aqueous MgCl₂ and CaCl₂ glasses were subjected to pulse radiolysis at 87 K. The time evolution and concentration dependence of e^-_t optical absorption spectra was examined.For MgCl₂ glasses the increase of Mg²⁺ concentration from 2.6 to 5 mol dm^-3 is followed by the shift of λ_max from 665 to 615 nm. For CaCl₂ glasses the concentration change from 3.1 to 4.5 mol dm^-3 Ca²⁺ causes the shift of λ_max from 625 to 590 nm. The blue shift is also observed during partial decay of e^-_t on μs time scale.With increasing concentration of electrolyte the contribution of e^-_ir to the total e^-_t absorption decreases, whereas that of e^-_vis increases.The ratio of [e^-_ir]/[e^-_vis] measured on micro-second time scale is significantly higher for Mg²⁺ than Ca²⁺ glasses.     

Determination of carbonate in the presence of hydroxide: Part 2. Evidence for the existence of a novel species from first-derivative potentiometric titration curves

An additional maximum has been detected in the differential potentiometric titration of mixtures of sodium hydroxide and sodium carbonate with hydrochloric acid using pH-responsive glass electrodes. This maximum is not detected under the following conditions: if ethanol (mol fraction >0.2) or t-butanol (mol fraction >0.1) is added; when the temperature is raised above 55°C; when hydrogen gas is bubbled through the solution; if a hydrogen gas electrode is used instead of the glass electrode; when carbonic anhydrase is added. The additional feature is ascribed to a new species HCO₃·H₂CO₃^- formed in solutions by a slow reaction.     

The electrokinetic study on the deposition of polystyrene latex onto Nylon fiber

Theζ-potentials of anionic polystyrene latex particles and Nylon fiber were measured as a function of concentration of NaCl, Na₂SO₄, Na₃PO₄ and CaCl₂, and the deposition of the latex onto Nylon fiber was considered. In the range of ionic strength from 5×10^?4 to 5×10^?2 where the rate of deposition was measured, the increase of electrolyte concentration resulted in the slight increase due to the adsorption of negative ion in the negativeζ-potentials of the latex particles. However, the rate of deposition increased with increasing concentration of electrolyte because of the decrease due to compression of the electrical double layer in the negativeζ-potentials of Nylon fiber. This result was supported by the fact that the maximum repulsive energy between electrical double layers of a latex particle and Nylon fiber decreased, as predicted theoretically, with decreasing ratio of theζ-potential of the fiber to that of the latex particle.     

Enhancing Capacity Performance by Utilizing the Redox Chemistry of the Electrolyte in a Dual‐Electrolyte Sodium‐Ion Battery

A strategy is described to increase charge storage in a dual electrolyte Na‐ion battery (DESIB) by combining the redox chemistry of the electrolyte with a Na⁺ ion de‐insertion/insertion cathode. Conventional electrolytes do not contribute to charge storage in battery systems, but redox‐active electrolytes augment this property via charge transfer reactions at the electrode–electrolyte interface. The capacity of the cathode combined with that provided by the electrolyte redox reaction thus increases overall charge storage. An aqueous sodium hexacyanoferrate (Na₄Fe(CN)₆) solution is employed as the redox‐active electrolyte (Na‐FC) and sodium nickel Prussian blue (Na_x‐NiBP) as the Na⁺ ion insertion/de‐insertion cathode. The capacity of DESIB with Na‐FC electrolyte is twice that of a battery using a conventional (Na₂SO₄) electrolyte. The use of redox‐active electrolytes in batteries of any kind is an efficient and scalable approach to develop advanced high‐energy‐density storage systems.     

Weak specific adsorption of ions

It is shown that the weak specific adsorption of ions not involving the recharging of the electrode surface is characterized by the following unusual features: practical absence of any shift of p.z.c.; a very small discrepancy between the experimental differential capacity curves and similar curves calculated under the assumption that specific adsorption is absent (q₁ = 0); insensitivity of the total surface excess of cations to their distribution between the dense and diffuse layers; practical independence of q₁ of temperature and the bulk concentration of binary electrolyte; practical coincidence of c.t.p. calculated for different concentrations of surface-active supporting electrolyte assuming q₁ = 0. It is also shown on the basis of the experimental data for the system {mc CsCl + (1 ? m)c LiCl} that the main fraction of the effective charge, determined by the mixed electrolyte method of Hurwitz—Parsons, results from the true specific adsorption of Cs⁺ cations at the Hg/H₂O interface and only a small fraction of this charge (?20%) can be associated with different positions of the o.H.p. for Li⁺ and Cs⁺ ions.     

The short-term cycling properties of Na/PVdF/S battery at ambient temperature

The Na/PVdF/S cells were composed of solid sodium, sulfur, and polyvinylidene fluoride–hexafluoropropene (PVdF) gel polymer electrolyte. The PVdF polymer electrolyte was prepared form tetraglyme plasticizer and NaCF₃SO₃ salt, and its electrochemical properties were studied using CV and impedance analysis. The interfacial resistance between sodium and polymer electrolyte increase with storage time, which might be associated with passivation layer. Solid-state sodium/sulfur cell using a PVdF gel polymer electrolyte has been tested. The Na/PVdF/S cell with 0.288 mA cm^?2 shows a high discharge capacity of 392 mAh g^?1 and 36 mAh g^?1 after 20 cycles. The cycle performance of Na/GPE/S cell operating at 25 °C is worse than Na/S cell at a high temperature.     

A highly efficient electric additive for enhancing photovoltaic performance of dye-sensitized solar cells

N-cetylpyridinium iodide (N-CPI) as a new electric additive for enhancing photovoltaic performance of the dye-sensitized solar cell (DSSC) was studied. It showed high efficiency for enhancing both the open-circuit voltage and the short-circuit current density of DSSC when the suitable amount of N-CPI as 0.02 M was added in liquid electrolyte. The energy conversion efficiency of DSSC increased from 4.429% to 6.535%, with 47.55% enhancement. Therefore, it is a highly efficient electric additive for DSSC. The intrinsic reason is owing to the special molecular structure of N-CPI, which contains two different polarity groups. As a surfactant, N-CPI could form ordered arrangement in liquid electrolyte, which affects the diffusing ability and the redox reaction of I^?/I ₃ ^? , and further affects the photovoltaic performance of DSSC.     

Experiments on solvated electron generation and deposition in hexamethylphosphoramide

Theory is developed and compared to experiment for the cyclic voltammetric ejection and redeposition of solvated electrons e_s^? in NaClO₄ and LiCl solutions in HMPA. In current reversal chronopotentiometry, e_s^? mass transfer can be observed free from uncompensated resistance effects by cathodic generation of e_s^? for time t_f followed by anodic current redeposition leading to a reverse transition time τ_b. The ratio τ_b/t_f depends on t_f, applied current, and LiCl electrolyte concentration. Comparison of τ_b/t_f to theory detects a highly reactive scavenger at micromolar concentration levels.     

CZE and ESI-MS of Borate-Sugar Complexes

Capillary zone electrophoresis (CZE) with electrospray ionization (ESI) mass spectrometry (MS) was used to study borate (B^?1) and sugar (L) complexes (L _x B^?1). Boric acid was adjusted to pH 10 with ammonium hydroxide to create an ESI-MS compatible CZE background electrolyte. We show for the first time that the electrophoretic peaks for each injected sugar contained both the substrates (i.e., sugar and/or multimers) and products (i.e., L _x B^?1). The effects of sheath liquid, temperature, and borate concentration were studied. The molecular mass information obtained from the ESI-MS provided new evidence on the mechanisms of borate-sugar complexation. Direct infusion ESI-MS and CZE-ESI-MS experiments strongly suggest that the formation of L _x B^?1 was from the direct reaction of a sugar or sugar multimer (L _x ) and B^?1. Larger L _x B^?1, where x > 2 were observed. Separation in the CZE dimension allows for the simultaneous analysis of a sugar mixture and simplified the ESI-MS analysis of sugars of the same molecular mass. The increase in sugar electrophoretic mobility caused by the increase in borate concentration was discussed in terms of the formation of L _x B^?1 complexes. In addition, the separation of five nucleosides by CZE using a borate electrolyte and detection using ESI-MS is demonstrated.     

The Influence on Interfacial Tension of the Combination of Anionic and Cationic Surfactants: Alkyl Sulfonate/Alkyltrimethylammonium Bromide

Mioellization of aqueous mixture of sodium octyl sulfonate ( C₈As )/ cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfonate (C₁₂As)( CTAB in the presence of sodium bromide has been studied by surface tension measurement. Nonideal solution theory has been used to calculate the molecular interaction parameters (β^M and β^s). The oil-aqueous interfacial tensions of C₁₂As/ CTAB, C₈As/CTAB, C₁₂As/dodecyl trimethylammonium bromide (DTAB) systems were also measured. We studied the influence of the surfactant concentration, surfactant molar fraction ratio, hydrocarbon chain length, added NaCl and alcohol concentration on the interfacial tension.