Low-conductivity background electrolytes in capillary zone electrophoresis--myth or reality?

The asymmetric triangle (fronting or tailing) concentration profiles and their broadening are the typical results of the electromigrational zone dispersion characterizing a system of the analyte in the background electrolyte (BGE). The present contribution suggests the parameter named the relative velocity slope, SBGE,X, which was introduced here as a quantity characterizing the peak broadening and the asymmetry. SBGE,X VS. analyte ionic mobility diagrams are suitable for the comparison of BGEs of given pH and the conductivity composed of electrolytes of different pKaS and ionic mobilities. The concept of SBGE,X diagrams is verified by capillary zone electrophoresis of the model analytes, which involve (i) the series of sulfobenzoylated poly(ethylene glycols) as examples of the strong electrolytes with different ionic mobilities and (ii) the series of monobasic phenols as weak electrolytes with different pKaS and similar ionic mobilities. It follows from both theoretical predictions of peak symmetry and their experimental verification that the optimum composition of BGEs is determined mostly by the suitable ionic mobility of the coion in dependence on the ionic mobility of the analyte. The low-conductivity BGEs based on low-molecular carrier ampholytes are at best only comparable with the properly chosen monobasic electrolytes.     

Selection of hydrogel electrolytes for flexible zinc–air batteries

Flexible zinc–air batteries attract more attention due to their high energy density, safety, environmental protection, and low cost. However, the traditional aqueous electrolyte has the disadvantages of leakage and water evaporation, which cannot meet application demand of flexible zinc–air batteries. Hydrogels possessing good conductivity and mechanical properties become a candidate as the electrolytes of flexible zinc–air batteries. In this work, advances in aspects of conductivity, mechanical toughness, environmental adaptability, and interfacial compatibility of hydrogel electrolytes for flexible zinc–air batteries are investigated. First, the additives to improve conductivity of hydrogel electrolytes are summarized. Second, the measures to enhance the mechanical properties of hydrogels are taken by way of structure optimization and composition modification. Third, the environmental adaptability of hydrogel electrolytes is listed in terms of temperature, humidity, and air composition. Fourth, the compatibility of electrolyte–electrode interface is discussed from physical properties of hydrogels. Finally, the prospect for development and application of hydrogels is put forward.     

Brønsted acid-base ionic liquids for fuel cell electrolytes

A simple protic ionic liquid obtained from the combination of diethylmethylamine and trifluoromethanesulfonic acid exhibits the remarkable results as a medium temperature fuel cell electrolyte under non-humidifying conditions, affording a higher and stable open-circuit potential, wide liquid temperature range, and high thermal stability.     

Near critical electrolytes: Are the charge-charge sum rules obeyed?

In an electrolyte solution the charge-charge structure factor obeys S(ZZ)(k;T,ρ)=0+ξ(Z,1) (2)k(2)-ξ(Z,2) (4)k(4)+? , where ξ(Z, 1) and ξ(Z, 2) are the second- and fourth-moment charge-charge correlation lengths depending on the temperature T and the overall ion density ρ. The vanishing of the leading term, the first Stillinger-Lovett (SL) sum rule, simply reflects bulk electroneutrality. The second SL rule, or second-moment condition, dictates that ξ(Z, 1) = ξ(D), where the Debye screening length ξ(D) is proportional to T/ρ. In this paper we present results from grand canonical Monte Carlo simulations of a fully size and charge symmetric 1:1 (finely-discretized) hard-sphere electrolyte, or restricted primitive model. By design, electroneutrality is imposed during the simulations, so satisfying the first sum rule automatically. However, careful finite-size scaling analyses of extensive histogram reweighted data indicate that the second-moment condition is violated at criticality, ξ(Z,1) (c) exceeding ξ(D) (c) by approximately 8%. It is also found that ξ(Z,2) (4) diverges to +∞ as T → T(c) in a manner closely mirroring the density-density fluctuations, S(NN)(0). These findings contradict generalized Debye-Hu?ckel theory and also the exactly soluble charge-symmetric spherical models, both of which support the second-moment condition at criticality and the finiteness of the fourth-moment. Nevertheless, the observed behavior is strikingly similar to that of the charge-asymmetric spherical models.     

Quantized electroluminescence from Q–CdS films immersed in aqueous electrolytes

Quantum dot electrodes (QDEs) have been constructed by deposition of Q–CdS particles onto indium–tin oxide substrates. Upon application of cathodic potentials to the electrodes in electrolytes containing persulfate ions (S₂O₈²⁻), light emission is observed. The emission peak depends on the particle size, with electrolyte electroluminescence (EEL) being observed down to 478 nm (blue light) for CdS with a particle size of 3.6 nm.     

Electrodeposition of iron–molybdenum–tungsten coatings from citrate electrolytes

Specific features of the electrodeposition of iron–molybdenum–tungsten coatings from citrate electrolytes based on iron(III) sulfate in the dc mode and with a unipolar pulsed current were studied. It was shown that varying the relative concentrations of salts of alloy-forming metals and the solution pH makes it possible to obtain lustrous compact coatings with low porosity and various contents of high-melting components. The effect of temperature on the coating composition and current efficiency was examined. The current density ranges providing high electrolysis efficiency were found and it was demonstrated that using a pulsed current favors formation of more compositionally homogeneous surface layers at a smaller amount of adsorbed nonmetallic impurities in the coatings. The iron–molybdenum–tungsten coatings are X-ray-amorphous and have better physicomechanical properties and corrosion resistance as compared with the base, which makes it possible to recommend these coatings for application in techniques for surface reinforcement and restoration of worn-out articles.     

Acceleration of carbon-13 spin-lattice relaxation times in amino acids by electrolytes

A series of amino acids and carboxylic acids were determined by C NMR spectroscopy. 13 The results showed that addition of 3M MgCl2 led to the C NMR integral area of samples being 13 well proportional to number of carbon atoms that produce the particular signal with reliability over 95%. Measurements of C spin-lattice relaxation times (T1’s) are reported for a number of amino 13 acids. T1’s of all the carbons in amino acids generally tend to decrease with the increase of the c…     

LiF–CaH2 alumina electrolytes for intermediate temperature fuel cell applications

Hydrofluoride-based electrolytes with proton conduction have been successfully used in intermediate temperature fuel cell applications. Among the various hydrofluoride electrolytes, LiF–CaH₂ and its composite with Al₂O₃, i.e., LiF–CaH₂–Al₂O₃, are the most promising candidates which show more advantages than the other hydrofluorides. In this communication, we put our emphasis on the LiF–CaH₂–Al₂O₃ electrolytes and their applications for intermediate temperature fuel cells. Furthermore, new fuel cell processes from hydride ions, H⁻, and the electrochemical behaviour of LiF–CaH₂–Al₂O₃ electrolytes and fuel cells are discussed in more detail.     

Development of electrospun PVdF–PAN membrane-based polymer electrolytes for lithium batteries

Electrospun fibrous membranes of composites of polyvinylidene fluoride and polyacrylonitrile (PVdF–PAN–ESFMs) are prepared with different proportions of PAN (25, 50 and 75%, w/w). The morphology of the ESFMs is examined by field emission scanning electron microscopy (FESEM). FESEM image of PVdF–ESFM reveals that the fibers have uniform diameters and smooth surfaces. However, the fibers of PVdF–PAN–ESFMs are interconnected with large number of voids and cavities of different sizes. These voids are effectively utilized for the preparation of polymer electrolytes by loading lithium perchlorate dissolved in propylene carbonate. PVdF–PAN–ESFM with 25% PAN (designated as PVdF–PAN(25)–ESFM) could load a high amount of lithium salt with electrolyte uptake of more than 300%. PVdF–PAN(25)–ESFM electrolyte exhibits a high conductivity of 7.8 mS cm⁻¹ at 25 °C and electrochemically stable up to 5.1 V. Also, the addition of PAN into PVdF decreases the interfacial resistance with lithium electrode. PVdF–PAN–ESFM electrolytes have complementary advantageous characteristics of PVdF and PAN. The promising results reported here clearly indicate that polymer electrolytes based on PVdF–PAN–ESFMs are most suited for lithium batteries.     

Apparent molar volumes and compressibilities of electrolytes and ions in γ-butyrolactone

The densities of tetraphenylphosphonium bromide, sodium tetraphenylborate, lithium perchlorate, sodium perchlorate and lithium bromide in γ-butyrolactone at (288.15, 293.15, 298.15, 303.15, 308.15 and 313.15) K and speed of sound at 298.15 K have been measured. From these data apparent molar volumes V_Φ at (288.15, 293.15, 298.15, 303.15, 308.15 and 313.15) K and the apparent molar isentropic compressibility K_S,Φ, at T = 298.15 K of the salts have been determined. The apparent molar volumes and the apparent molar isentropic compressibilities were fitted to the Redlich, Rosenfeld and Mayer equation as well as to the Pitzer and Masson equations yielding infinite dilution data. The obtained limiting values have been used to estimate the ionic data of the standard partial molar volume and the standard partial isentropic compressibility in γ-butyrolactone solutions.     

All-solid-state Li/S batteries with highly conductive glass–ceramic electrolytes

All-solid-state cells using sulfur-based cathode materials and Li₂S–P₂S₅ glass–ceramic electrolytes were successfully prepared and exhibited excellent cycling performance at room temperature. The cathode materials consisting of sulfur and CuS were synthesized by mechanical milling using sulfur and copper crystals as starting materials. The cell performance was influenced by the milling time for the cathode materials and the cell with cathode materials obtained by milling for 15 min retained large capacities over 650 mA h g⁻¹ for 20 cycles. Sulfur as well as CuS in cathode materials proved to be utilized as active materials on charge–discharge processes in the all-solid-state Li/S cells.     

Cross-linking copolymers of acrylates’ gel electrolytes with high conductivity for lithium-ion batteries

The cross-linking gel copolymer electrolytes containing alkyl acrylates, triethylene glycol dimethacrylate, and liquid electrolyte were prepared by in situ thermal polymerization. The gel polymer electrolytes containing 15 wt% polymer content and 85 wt% liquid electrolyte content with sufficient mechanical strength showed the high ionic conductivity around 5?×?10^?3 Scm^?1 at room temperature. The gel electrolytes containing different polymer matrices were prepared, and their physical observation and conductivity were discussed carefully. The cross-linking copolymer gel electrolytes of alkyl acrylates with other monomers were designed and synthesized. The results showed that copolymerization can improve the mechanical properties and ionic conductivities of the gel electrolytes. The polymer matrices of gels had excellent thermal stability and electrochemical stability. The scanning electron microscope analysis showed the gel electrolyte was the homogeneous structure, and the cross-linking polymer host was the porous three-dimensional network structure, which demonstrated the high conductivity of the gel electrolytes. The gel polymer Li-ion battery was prepared by this in situ thermal polymerization. The cell exhibited high charge-discharge efficiency at 0.1 C. The results of LiFePO4-PEA-Li cell and graphite-PEA-Li cell showed that gel polymer electrolytes have good compatibility with the battery electrodes materials.     

Lithium bis(oxalate)borate crosslinked polymer electrolytes for high-performance lithium batteries

Solid electrolytes play a vital role in solid-state Li secondary batteries,which are promising high-energy storage devices for new-generation electric vehicles.Nevertheless,obtaining a suitable solid electrolyte by a simple and residue-free preparation process,resulting in a stable interface between electrolyte and electrode,is still a great challenge for practical applications.Herein,we report a self-crosslinked polymer electrolyte(SCPE)for high-performance lithium batteries,prepared by a one-step method based on 3-methoxysilyl-terminated polypropylene glycol(SPPG,a liquid oligomer).It is worth noting that lithium bis(oxalate)borate(Li BOB)can react with SPPG to form a crosslinked structure via a curing reaction.This self-formed polymer electrolyte exhibits excellent properties,including high roomtemperature ionic conductivity(2.6×10^-4 S cm^-1),wide electrochemical window(4.7 V),and high Li ion transference number(0.65).The excellent cycling stability(500 cycles,83%)further highlights the improved interfacial stability after the in situ formation of SCPE on the electrode surface.Moreover,this self-formation strategy enhances the safety of the battery under mechanical deformation.Therefore,the present self-crosslinked polymer electrolyte shows great potential for applications in high-performance lithium batteries.     

Preparation of safe water–lipid mixed electrolytes for application in ion capacitor

Aqueous electrolytes are safe, economic, and environmentally friendly. However, they have a narrow potential window. On the other hand, organic electrolytes exhibit good thermodynamic stability but are inflammable and moisture sensitive. In this study, we prepared water–PEG–lipid ternary electrolytes(TEs). To combine the advantages of water, polyethylene glycol(PEG) and propylene carbonate(PC). The nonflammable mixed electrolytes exhibited a wide potential window of about 2.8 V due to the beneficial effects of PEG and PC. Using these TEs, a lithium manganate–active carbon ion capacitor could be operated at 2.4 V with an energy density of 32 Wh/kg, based on the total active electrode material(current density of 3.3 m A/cm~2). This value was significantly higher than that achieved using an aqueous electrolyte, thereby rationalizing the higher energy density.     

Nanoporous oxide formation by anodic oxidation of Nb in sulphate–fluoride electrolytes

The influence of hydrofluoric acid (HF) concentration and applied potential on the processes of anodic oxidation of Nb in sulphuric acid solution was studied by chronoamperometry, electrochemical impedance spectroscopy and scanning electron microscopy. During the first stage of the process, a compact barrier film is formed. On top of this film, a porous overlayer starts to form, then the nanopores grow into an ordered nanostructure. Subsequently, secondary 3D flower-shaped structures begin to form. These structures gradually spread all over the surface as an irregular multilayer film. The rates of the process of porous overlayer formation and subsequent growth of nanopore arrays increase with applied potential as well as with the HF concentration. The films have been characterised ex situ by electrochemical impedance spectroscopy at open circuit potential and capacitance vs. potential measurements to follow the different stages of nanoporous film formation with electrochemical methods. The impedance spectra and capacitance vs. potential curves have been interpreted using previously proposed models for the amorphous semiconductor/electrolyte interface. An attempt to rationalise the mechanism of nanoporous layer growth is presented by using the conceptual views of the mixed-conduction model and recent ideas for porous film formation on valve metals.     

Influence of valence and concentration of electrolytes on the ζ-potential of polyacrylic lattices

The -potential of copolymer particles of acrylic amide, acrylic acid, acrylic butyl ester, and styrene were measured in different electrolyte solutions. In an isotonic solution of sodium chloride, they vary with the content of acrylic acid between –36 mV and –49 mV. In the presence of 21-electrolytes, the -potential could be correlated with the logarithm of the electrolyte concentration. The 21-electrolytes predominantly determine the -potential of the particles not only in the solutions of these electrolytes, but also in mixed electrolyte solutions. In the presence of human serum, the electrophoretic mobility increases with increasing acrylic acid content of the polymer.     

‘‘Soggy sand＇＇ polymer composite nanofber membrane electrolytes for lithium ion batteries

A kind of octanol-modifded silica nanoparticle was fabricated and employed as a framework to form‘‘soggy sand’’electrolyte along with 1-butyl-3-methylimidazolium tetrafluoroborate.‘‘Soggy sand’’and poly（vinylidene fluoride-hexafluoropropylene）composite electrolyte membranes were electrospun for the frst time.The properties of this membrane electrolyte have been evaluated by the mechanical test and electrochemical test.The Young’s modulus increased by 275%from 6.8 MPa to 25.5 MPa and the electrical conductivity increased to 7.6 10à5S/cm at 290.15 K when compared to pristine P（VdF-HFP）membrane electrolyte.The conductivity is 3.1 10à4S/cm at 323.15 K.     

Enthalpies of dilution for 1∶3 and 3∶1 electrolytes aqueous solutions

The enthalpies of dilution for aqueous solutions of [Co(cn)₃)]Cl₃, [Co(pn)₃)]Cl₃ and [Co(tn)₃]Cl₃, (whereen=1,2-diaminoethane,pn=1,2-diaminopropane, andtn=1,3-diaminopropane) have been measured at 298.15 K, and up to 1 mol kg^–1+, using a new large isoperibol calorimeter by the long-jump method. Relative apparent molar enthalpies,_291-01, have been extracted as an empirical equation relatingL andm. We have compared our complex salts with the 31 and 13 aqueous systems found in the literature. Theoretical predictions for 13 and 31 electrolytes in the Restricted Primitive Model are also shown.This work was supported in part by CICYT (M.E.C., Spain) under Research Project No.: PB92-0553.     

Investigation on the effect of nanosilica towards corn starch–lithium perchlorate-based polymer electrolytes

Biodegradable corn starch–lithium perchlorate (LiClO₄)-based solid polymer electrolytes with addition of nano-sized fumed silica (SiO₂) were prepared by solution casting technique. Ionic conductivity at ambient temperature was measured by AC impedance spectroscopy. Upon addition of nano-sized SiO₂, the ionic conductivity at room temperature is increased. The optimum ionic conductivity value obtained was 1.23?×?10^?4?S?cm^?1 at 4?wt% SiO₂. This may be attributed to the low crystallinity of the polymer electrolytes resulting from the dispersed nanosilica particles. Fourier–transform infrared spectroscopy studies confirmed the complexation between corn starch, lithium perchlorate, and silica. The thermal properties of the prepared samples were investigated with differential scanning calorimetry and thermogravimetric analysis. The surface morphology of the polymer electrolytes confirmed the agglomeration of particles after excess dispersion of inorganic filler. This was proven in the scanning electron microscopy studies.