Addition Of Lithium Salt Research Articles

Ion-specific and charge effects in counterion binding to poly(styrenesulfonate) anions

In order to obtain a deeper insight into effects occurring when an electrolyte solution is added to a solution of a strong polyelectrolyte, the microcalorimetric and potentiometric titrations of poly(sodium 4-styrenesulfonate) (Na(+)PSS(-)) solution with different alkali, earth-alkali and tetraalkylammonium nitrate, perchlorate and chloride solutions were performed. From the calorimetric titrations the differences in sign and magnitude of enthalpy change upon addition of various electrolytes were observed depending on the salt used. Potentiometric titrations using a sodium ion selective electrode have revealed that addition of an electrolyte is accompanied by the increase in sodium activity until a certain critical value is reached, which seems to be the consequence of counterion substitution on the polyelectrolyte chain. In the case of addition of lithium and sodium salts the experimental results for ΔH of mixing can be qualitatively correctly explained by the Poisson-Boltzmann and Monte Carlo calculations based on the continuum solvent models. This is not the case for the mixtures with KNO(3), RbNO(3) and CsNO(3) salts. The results suggest that the ion-specific effects, associated with the changes in the water structure, have to be taken into account when thermodynamic properties of polyelectrolytes in solution are concerned. The calorimetric results imply that the enthalpically observed cation specificity for binding to a poly(styrenesulfonate) group could be correlated with corresponding cation hydration enthalpies. The counterion substitution of sodium with divalent cations was found to be endothermic, which is in qualitative agreement with the electrostatic theory.

Thermal Stabilities of Some Lithium Salts and Their Electrolyte Solutions With and Without Contact to a LiFePO4 Electrode

Thermal stabilities of different lithium salts and the roles of the salts on the thermal behaviors of their based electrolytes and electrolyte– coexisting systems were analyzed by a C80 microcalorimeter in this paper. For the salts lithium hexafluorophosphate , lithium tetrafluoroborate , lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), and lithium bis(oxalate)borate (LiBOB), there is no exothermic behavior was detected. The mixture systems without lithium salts present relatively stable thermal behavior. The thermal stability of solvents is greatly reduced after the addition of lithium salt, especially for the -based electrolyte. The special structure and composition of LiBOB enable the LiBOB-based electrolyte to show excellent thermal stability. The thermal stability of the electrolyte– coexisting system is mainly determined by the electrolyte not by and the LiBOB-based coexisting system shows better thermal characteristics.

ChemInform Abstract: Diastereoselective Synthesis of 2,5-Substituted Tetrahydrofurans by Intramolecular Alkylation of an Ester Enolate.

Highly diastereoselective cyclization is carried out by the intramolecular alkylation of an ester enolate of t-butyl α-alkoxyacetates. The addition of lithium salt enhances the diastereoselectivity of the reaction to afford 2,2,5-trisubstituted tetrahydrofurans.

Room Temperature Ionic Liquid−Lithium Salt Mixtures: Optical Kerr Effect Dynamical Measurements

The addition of lithium salts to ionic liquids causes an increase in viscosity and a decrease in ionic mobility that hinders their possible application as an alternative solvent in lithium ion batteries. Optically heterodyne-detected optical Kerr effect spectroscopy was used to study the change in dynamics, principally orientational relaxation, caused by the addition of lithium bis(trifluoromethylsulfonyl)imide to the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. Over the time scales studied (1 ps-16 ns) for the pure ionic liquid, two temperature-independent power laws were observed: the intermediate power law (1 ps to approximately 1 ns), followed by the von Schweidler power law. The von Schweidler power law is followed by the final complete exponential relaxation, which is highly sensitive to temperature. The lithium salt concentration, however, was found to affect both power laws, and a discontinuity could be found in the trend observed for the intermediate power law when the concentration (mole fraction) of lithium salt is close to chi(LiTf(2)N) = 0.2. A mode coupling theory (MCT) schematic model was also used to fit the data for both the pure ionic liquid and the different salt concentration mixtures. It was found that dynamics in both types of liquids are described very well by MCT.

Effect of consumption amount of lithium salt on the properties of LiFePO 4/C cathode materials

LiFePO 4/C composites were synthesized by carbothermal reduction method and the effect of consumption amount of lithium salt on the properties of LiFePO 4/C materials was systematically investigated. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), carbon/sulfur determinator and constant-current charge/discharge test. The results showed that the lithium salt addition should exceed the theoretical value in order to make up for the lithium ion loss during the synthesis and SEI film formation process and the resulting carbon contents in these samples were all about 2.3 wt%. The optimal addition of lithium salt was 8% excess of the theoretical value. Electrochemical results showed that the optimal sample exhibited high discharge capacities of 157.6 and 143.5 mAh/g at 0.2 C and 1 C rates, respectively. The capacity was reduced to 128.8 mAh/g after 100 cycles at 2 C rate, with a cycling capacity retention rate of 99.8%.

Effects of anionic structure and lithium salts addition on the dissolution of cellulose in 1-butyl-3-methylimidazolium-based ionic liquid solvent systems

Cellulose is the most abundant biorenewable and biodegradable resource on the earth. However, the extent of its application is limited due to its inefficient dissolution in solvents. Thus, the development of new cellulose solvents continues to be an active area of investigation. In this work, a series of ionic liquids (ILs) have been synthesized by coupling the 1-N-butyl-3-methylimidazolium cation [C4mim]+ with the Bronsted basic anions [CH3COO]−, [HSCH2COO]−, [HCOO]−, [(C6H5]COO]−, [H2NCH2COO]−, [HOCH2COO]−, [CH3CHOHCOO]− and [N(CN)2]−. The solubilities of microcrystalline cellulose (MCC) in these ionic liquids were determined as a function of temperature. The effect of the anion structure on the solubility of cellulose has been estimated, and investigated by 1H NMR and a solvatochromic UV/vis probe. It was found that the solubility of cellulose increases almost linearly with increasing hydrogen bond accepting ability of anions in the ionic liquids. At the same time, novel [C4mim][CH3COO]/lithium salt (LiCl, LiBr, LiAc, LiNO3, or LiClO4) solvent systems have been developed by adding 1.0 wt% of lithium salt into [C4mim][CH3COO]. It was shown that the addition of lithium salts significantly increased the solubility of the cellulose. This observation was studied by 13C NMR spectra, and the results suggested that the enhanced solubility of cellulose originated from the disruption of the intermolecular hydrogen bond, O(6)H⋯O(3) owing to the interaction of Li+ with the hydroxyl oxygen O(3) of cellulose. Furthermore, the cellulose materials regenerated from the ionic liquids were characterized by scanning electron micrograph, thermogravimetric analysis and Fourier transform infrared spectroscopy, and the degree of polymerization of the original and regenerated cellulose materials was also determined. Good thermal stability was found for the regenerated cellulose. It is expected that the above information is useful for the design of novel ionic liquids and ionic liquid-based solvent systems for cellulose.

PREPARATION AND CHARACTERISTICS OF NOVEL HYPERBRANCHED PEU-BASED GEL POLYMER ELECTROLYTES

Gel polymer electrolytes (GPEs) based on hyperbranched poly (ether urethane) (PHEU) were prepared from the reaction of the hyperbranched polyether (PHEMO) with different diisocyanates in liquid electrolyte. The ionic conductivities and transference number of the GPEs were investigated by alternating current (AC) impedance and multi-potential steps. It is found that the ionic conductivities of GPEs were influenced by diisocyanate structure, lithium salt concentration and addition amount of liquid electrolyte. Sample PUM-0.5M-80% originated from 4, 4-diphenylmethane diisocyanate (MDI) as the hard segment shows the highest ionic conductivity of 2.41×10-3 Scm-1 at ambient temperature. The lithium ion transference number is 0.7. In addition, small molecules of liquid electrolyte were perfectly entrapped by polymer matrix, and liquid leakage in lithium ion battery was avoided. 5 . The hard segment provides good mechanical strength, while the soft segment improves the ionic conductivity. The rubbery soft segments can dissolve alkali metal salts, and help achieving high ion mobility, which originates from the interaction of the ether oxygen with the alkali metal ions. In the previous report 6 , the hyperbranched polyether (PHEMO) without stiff groups is selected as soft segment, as well as its amorphous state inherently derived from the hyperbranched molecular structure. Therefore, PHEMO is expected to improve the ionic conductivity of polymer electrolyte 7 . Due to their good mechanical properties, diisocyanates are chosen to act as hard segment domains contributing to the dimensional stability of the polymer electrolytes 8 . In this paper, GPEs based on PHEU were prepared with hyperbranched polyether (PHEMO) and diisocyanates in liquid electrolyte. Diisocyanates with different structures, such as aliphatic isocyanates of hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI), or aromatic isocyanates of 4, 4-diphenylmethane diisocyanate (MDI) and 2, 4-tolune diisocyanate (TDI) were served as hard segments, respectively. The effects of diisocyanate structure, lithium salt concentration and addition amount of electrolyte on the ionic conductivities of the as-prepared GPEs were discussed and compared.

Enhanced charge mobility in a molecular hole transporter via addition of redox inactive ionic dopant: Implication to dye-sensitized solar cells

Upon the addition of lithium salts to the hole-transporter matrix, 2,2′,7,7′-tetrakis(N,N-di-p-methoxypheny-amine)-9,9′-spirobifluorene (spiro-MeOTAD), the authors observe a 100-fold increase in conductivity through spiro-MeOTAD within a TiO2 mesoporous network. The authors demonstrate this to be a bulk effect and not due to improved injection at the electrodes. By testing “hole-only” diodes of pure spiro-MeOTAD and those doped with lithium salts, the authors calculate that the hole mobility increases from 1.6×10−4to1.6×10−3cm2∕Vs. The authors discuss the possible mechanisms for this significant enhancement in charge mobility and its implication to the dye-sensitized solar cell operation.

The Importance of Alkali Cations in the [{RuCl2(p‐cymene)}2]–Pseudo‐dipeptide‐Catalyzed Enantioselective Transfer Hydrogenation of Ketones

We studied the role of alkali cations in the [{RuCl2(p-cymene)}2]-pseudo-dipeptide-catalyzed enantioselective transfer hydrogenation of ketones with isopropanol. Lithium salts were shown to increase the enantioselectivity of the reaction when iPrONa or iPrOK was used as the base. Similar transfer-hydrogenation systems that employ chiral amino alcohol or monotosylated diamine ligands are not affected by the addition of lithium salts. These observations have led us to propose that an alternative reaction mechanism operates in pseudo-dipeptide-based systems, in which the alkali cation is an important player in the ligand-assisted hydrogen-transfer step. DFT calculations of the proposed transition-state (TS) models involving different cations (Li+, Na+, and K+) confirm a considerable loosening of the TS with larger cations. This loosening may be responsible for the fewer interactions between the substrate and the catalytic complex, leading to lower enantiodifferentiation. This mechanistic hypothesis has found additional experimental support; the low ee obtained with [BnNMe3]OH (a large cation) as base can be dramatically improved by introducing lithium cations into the system. Also, the complexation of Na+, K+, and Li+ cations by the addition of [15]crown-5 and [18]crown-6 ethers and cryptand 2.1.1 (which selectively bind to these cations and, thus, increase their bulkiness), respectively, to the reaction mixture led to a significant drop in the enantioselectivity of the reaction. The lithium effect has proved useful for enhancing the reduction of different aromatic and heteroaromatic ketones.

Extremely strong solvent dependence of the S1→ S0internal conversion lifetime of 12′-apo-β-caroten-12′-al

The ultrafast internal conversion (IC) dynamics of the carbonyl carotenoid 12'-apo-beta-caroten-12'-al has been investigated in solvents of varying polarity using time-resolved femtosecond transient absorption spectroscopy. The molecules were excited to the S(2) state by a pump beam of either 390 or 470 nm. The subsequent intramolecular dynamics were detected at several probe wavelengths covering the S(0)--> S(2) and S(1)--> S(n) bands. For the S(1)--> S(0) internal conversion process, a remarkably strong acceleration with increasing polarity was found, e.g., lifetimes of tau(1) = 220 ps (n-hexane), 91 ps (tetrahydrofuran) and 8.0 ps (methanol) after excitation at 390 nm. The observation can be rationalized by the formation of a combined S(1)/ICT (intramolecular charge transfer) state in the more polar solvents. The effect is even stronger than the strongest one reported so far in the literature for peridinin. Addition of lithium salts to a solution of 12'-apo-beta-caroten-12'-al in ethanol leads only to small changes of the IC time constant tau(1). In addition, we estimate an upper limit for the time constant tau(2) of the S(2)--> S(1) internal conversion process of 300 fs in all solvents.

Short circuiting in a denitrifying activated sludge tank

The presence of a short circuit flow in a denitrifying activated sludge tank was identified and modelled. Tracer tests with pulse addition of lithium salt were used to investigate the hydraulics of the tank. The lithium concentration in the effluent was detected and residence time distribution (RTD) curves were generated. Hydraulic models based on completely stirred tank reactors (CSTRs) in series were generated from the RTD curves and the models were compared. The short circuit problem was successfully described using the Martin model, where the inflow is divided into two strands. Each strand was modelled as a number of CSTRs in series. At a normal flow the results of the model show that the tank has 12.8% dead volume, 85.8% main volume and 1.3% short circuiting volume. The inflow was divided into 91.9% entering the main volume and 8.1% entering the short circuiting volume. The mean velocity of the short circuiting stream was estimated to 0.4 m/s. At maximum flow the short circuiting stream was even larger and handled 24.3% of the flow. The short circuiting stream was identified in the upper part of the tank due to the position of the inlet and the outlet. The configuration of a tank including the use of baffles, the geometry of the inlet and mixer configuration should be considered carefully if short circuiting is to be avoided.

New Organic Dispersions of Conducting Polymers Using Polymeric Ionic Liquids as Stabilizers

AbstractSummary: Polypyrrole (PPy), polyaniline (PANI), and poly(ethylenedioxythiophene) (PEDOT) aqueous dispersions were prepared by polymerizing the corresponding monomer in the presence of a polymeric ionic liquid (PIL), poly(1‐vinyl‐3‐ethylimidazolium bromide). By addition of bispentafluoroethanesulfonimide lithium salt, the PIL stabilizer becomes hydrophobic and precipitates in water and traps the conducting polymer microparticles inside. The dispersion of the recovered powders in organic solvents leads to organic conducting dispersions. After casting the organic dispersions, hydrophobic films with electrical conductivity values as high as 0.1 S · cm−1 were obtained.A new synthetic route to new organic dispersions.magnified imageA new synthetic route to new organic dispersions.

Improved ionic conductivity of nitrile rubber/ionic liquid composites

Polymer electrolytes with high ionic conductivity and good elasticity were prepared by mixing nitrile rubber (poly(acrylonitrile-co-butadiene) rubber; NBR) with ionic liquid, N-ethylimidazolium bis(trifluoromethanesulfonyl)imide (EImTFSI). The NBR/EImTFSI composites were obtained as homogeneous and transparent films when the ionic liquid content was less than 60wt%. Raman spectroscopy suggested the interaction between nitrile group of NBR and TFSI anion. Sample with ionic liquid content of 50wt% showed the ionic conductivity of 1.2×10−5Scm−1 at 30°C. Addition of lithium salt to this NBR/EImTFSI composite further enhanced the ionic conductivity to about 10−4Scm−1 without spoiling mechanical properties. DSC studies showed two glass transition temperatures for composites indicating microphase separation.

Influence of LiClO4 on the thermal, mechanical, and morphological properties of P(DMS‐co‐EO)/ P(EPI‐co‐EO) blends

AbstractThe UV‐vis absorption, thermal analysis, ionic conductivity, mechanical properties, and morphology of a blend of poly(dimethylsiloxane‐co‐ethylene oxide) [P(DMS‐co‐EO)] and poly(epichlorohydrin‐co‐ethylene oxide) [P(EPI‐co‐EO)] (P(DMS‐co‐EO)/P(EPI‐co‐EO) ratio of 15/85 wt %) with different concentrations of LiClO4 were studied. The maximum ionic conductivity (σ = 1.2 × 10−4 S cm−1) for the blend was obtained in the presence of 6% wt LiClO4. The crystalline phase of the blend disappeared with increasing salt concentration, whereas the glass transition temperature (Tg) progressively increased. UV‐vis absorption spectra for the blends with LiClO4 showed a transparent polymer electrolyte in the visible region. The addition of lithium salt decreased the tensile strength and elongation at break and increased Young's modulus of the blends. Scanning electron microscopy showed separation of the phases between P(DMS‐co‐EO) and P(EPI‐co‐EO), and the presence of LiClO4 made the blends more susceptible to cracking. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1230–1235, 2004

Influence of both milling conditions and lithium salt addition on the sinterability of Ba(Zn 1/3Ta 2/3)O 3

The complex perovskite oxide Ba(Zn 1/3Ta 2/3)O 3 (BZT) has been largely studied for its interesting dielectric properties. This material possesses a relatively high dielectric constant associated with very low losses at usual frequency applications. It can be used as hyperfrequency resonators or capacitors. Unfortunately, a high sintering temperature is required to achieve high-density materials (>1500 °C), which is too high for industrial applications. The development of base metal electrode multi layer ceramic capacitors (BME MLCC) requires a low sintering temperature to be co-sintered with non-noble metals such as Ni and Cu. The technological process has been investigated with respect to milling conditions and calcination parameters to optimise each fabrication step. In addition, lithium salt (Li 2CO 3, LiF, BaLiF 3 and LiNO 3) additions have been tested to lower the sintering temperature. The BZT sintering temperature can be lowered to 200 °C when 15 mol% of LiF is added without modifying permittivity and loss factors at 1 MHz. Each sample was characterised in terms of density, microstructure and dielectric properties.

Transparent conducting polymer electrolyte by addition of lithium to the molecular complex chitosane–poly(aminopropyl siloxane)

Transparent lithium-ion conducting films were prepared by adding lithium perchlorate to a mixture of chitosane (CHI) and poly(aminopropylsiloxane) (pAPS) in a molar ratio 0.6:1 by sol–gel methods. The morphological and molecular properties, determined by scanning electron microscopy and FT-IR, respectively, depend on the lithium salt concentration. The same techniques were also used for performing a “titration” of the capacity of the film for incorporating lithium salt. Results show that about 0.8 mol lithium salt per mol chitosane can be added before the product losses the transparence and molecular compatibility characteristic of the pristine CHI/pAPS polymer complex. When lithium salt addition reaches the tolerance limit, anisotropically oriented patterns are observed in the hybrid films. Both transparence and ionic conductivity of the product appear to be related to the layered nature of formed nanocomposites. The properties of obtained films may be furthermore rationalized considering the chemical functionality and the Lewis donor–acceptor affinity of the components.

Functionalization of polymeric organolithium compounds with 3,4‐epoxy‐1‐butene: Precursors for diene‐functionalized macromonomers

AbstractThe functionalization of polymeric organolithiums (PLi) with 3,4‐epoxy‐1‐butene (EPB) in a hydrocarbon solution yielded the corresponding hydroxybutene‐functionalized polymers in high yields (>95%). Three modes of addition of PLi to EPB were observed (1,4, 3,4, and 4,3). The products and chain‐end structures were characterized by 1H NMR, 13C NMR, attached‐proton‐test 13C NMR, calculated 13C NMR chemical shifts, and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS). The regioselectivity of the addition depended on the PLi chain‐end structure, the reaction conditions, and the addition of lithium salts or Lewis bases. In the absence of additives, the functionalization of poly(styryl)lithium (PSli) produced equal amounts of 1,4‐, 3,4‐, and 4,3‐addition, as determined by quantitative 13C NMR analysis. The use of a low temperature (6 °C), inverse addition, the addition of triethylamine (TEA; [TEA]/[PSLi] = 20) as a Lewis base, or dienyllithium chain ends produced polymers with only the 1,4‐addition product. Mild dehydration of the hydroxybutene‐functionalized polymer with p‐toluenesulfonic acid produced the corresponding diene‐functionalized macromonomer, as shown by MALDI‐TOF MS. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 947–957, 2003

Effects of lithium salts on ASR gel composition and expansion of mortars

Suppression of alkali–silica reaction (ASR) expansion in mortar and concrete by the addition of lithium salts has been confirmed by some workers. It has been revealed that lithium hydroxide tended to reduce the reaction between sodium or potassium hydroxide and reactive silica, and that the ASR gel incorporating lithium was less expansive. However, it has not been reported how the addition of a lithium salt influenced the composition of the ASR gel. The calcium in ASR gel is considered to play an important role in the expansion of the gel. Thus, it is significant to characterize ASR gel composition in mortars containing lithium salts by BSE–EDS analysis. This study aims to discuss the mechanisms of suppression of ASR expansion in mortar by lithium salts from the viewpoint of ASR gel composition. The average CaO/SiO 2 ratio in ASR gels decreased with increasing amount of added lithium salts. It should be noted that the extent of variations in the CaO/SiO 2 ratio in ASR gels significantly decreased with increasing amount of lithium salts. The addition of relatively small amounts of LiOH and Li 2CO 3 resulted in increased expansion. We also obtained an unexpected result that ASR gels became homogeneous with respect to their CaO contents at high dosage levels. However, the reduction in average CaO/SiO 2 ratios and the homogenization in the CaO content of ASR gels due to the addition of lithium salts may not be related to the expansion of mortars.

Substituted polypyridine complexes of cobalt(II/III) as efficient electron-transfer mediators in dye-sensitized solar cells.

A number of cobalt complexes of substituted polypyridine ligands were synthesized and investigated as possible alternatives to the volatile and corrosive iodide/triiodide redox couple commonly used as an electron-transfer mediator in dye-sensitized solar cells (DSSCs). The extinction coefficients in the visible spectrum are on the order of 10(2) M(-1) cm(-1) for the majority of these complexes, diminishing competition with the light-harvesting dye. Cyclic voltammetric studies revealed a dramatic surface dependence of the heterogeneous electron-transfer rate, which is surprisingly different for gold, carbon, and platinum electrodes. DSSCs were assembled using a mediator that consisted of a mixture of Co(II) and Co(III) complexes in a 10:1 ratio. DSSCs containing these mediators were used to characterize incident photon-to-current conversion efficiency and photoelectrochemical responses. The best performing of these mediators were identified and subjected to further study. As suggested by electrochemical results, gold and carbon are superior cathode materials to platinum, and no evidence of corrosion on any cathode material was observed. Addition of lithium salts to the mediator solution resulted in a dramatic improvement in cell performance. The observed Li(+) effect is explained in terms of the recombination of injected electrons in the photoanode with the oxidized mediator. The best mediator, based on tris(4,4'-di-tert-butyl-2,2'-dipyridyl)cobalt(II/III) perchlorate, resulted in DSSCs exhibiting efficiencies within 80% of that of a comparable iodide/triiodide-mediated DSSC. Due to the commercial availability of the ligand and the simplicity with which the complex can be made, this new mediator represents a nonvolatile, noncorrosive, and practical alternative as an efficient electron-transfer mediator in DSSCs.

Sol-Gel Coatings of Nb 2 O 5 and Nb 2 0 5 :Li + :Electrochemical and Structural Characterization

Thin solid films of Nb 2 0 5 and Nb 2 O 5 :Li + were prepared by the sol-gel process using the sonocatalitic method from NbC1 5 as precursor and butanol as solvent. The addition of different lithium salt (LiCF 3 SO 3 ) quantities to the precursor solution produced films with different electrochemical performance. All the films showed the TT structure and the best opto-electrochemical responses were obtained with the films doped with 10% mol of lithium salt.