The effect of different lithium salts on conductivity of comb-like polymer electrolyte with chelating functional group

The behaviors of lithium ions in a comb-like polymer electrolyte with chelating functional group complexed with LiCF₃SO₃, LiBr and LiClO₄ were characterized by differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR) spectroscopy, AC impedance, and ¹³C solid-state NMR measurement. The comb-like copolymer was synthesized from poly(ethylene glycol) methyl ether methacrylate (PEGMEM) and (2-methylacrylic acid 3-(bis-carboxymethylamino)-2-hydroxy-propyl ester) (GMA-IDA). FT-IR spectra reveal the interactions of Li⁺ ions with both the ether oxygen of the PEGMEM and the nitrogen atom of the GMA-IDA segments. FT-IR spectra also indicate an increasing anion-cation association consistent with increasing LiCF₃SO₃ concentrations. Moreover, the ¹³C solid-state NMR spectra for the carbons attached to the ether oxygen atoms exhibited significant line broadening and a slight upfield chemical shift when the dopant was added to the polymer. These findings indicate coordination between the Li cation and the ether oxygens in the PEG segment. T_g and T_d of copolymers doped with salts clearly increase, as shown by DSC and TGA measurements. These results indicate the interactions of Li⁺ with both PEGMEM and GMA-IDA segments form transient cross-links inside the copolymers. The Vogel-Tamman-Fulcher (VTF)-like behavior of conductivity implies the coupling of the charge carriers with the segmental motion of the polymer chain in this study. The maximum conductivity of copolymers relates to the composition of the copolymers and the concentration of doping lithium ions. In summary, the GMA-IDA unit in the copolymer promotes the dissociation of the lithium salt, the mechanical strength and the conductivity of the polyelectrolyte.     

Prediction of gas solubility in binary polymer+solvent mixtures

This paper is devoted to a theory of gas solubility in highly asymmetrical mixed solvents composed of a low molecular weight (such as water, alcohol, etc.) and a high molecular weight (such as polymer, protein, etc.) cosolvents. The experimental solubilities of Ar, CH₄, C₂H₆ and C₃H₈ in aqueous solutions of polypropylene glycol and polyethylene glycol were selected for comparison with the theory. The approach for predicting these solubilities is based on the Kirkwood-Buff formalism for ternary mixtures, which allowed one to derive a rigorous expression for the Henry constant in mixed solvents. Starting from this expression, the solubilities could be predicted in terms of those in each of the two constituents and the properties of the mixed solvent. This expression combined with the Flory-Huggins equation for the activity coefficient in a binary mixed solvent provided very accurate results, when the Flory-Huggins interaction parameter was used as an adjustable quantity. A simple expression in which the solubility could be predicted in terms of those in each of the two constituents and the molar volumes of the latter was also derived. While less accurate that the previous expression, it provided more than satisfactory results.     

Influence of lithium difluorophosphate additive on the high voltage LiNi0.8Co0.1Mn0.1O2/graphite battery

Lithium-ion batteries (LIBs) possessing high energy densities are driven by the growing demands of electric vehicles (EVs) and hybrid electric vehicles (HEVs). One of the most effective strategies to improve the energy density of LIBs is to enlarge the charge cut-off voltage via a lithium salt additive for the conventional electrolyte system. Herein, lithium difluorophosphate (LIDFP) is employed to optimize and reconstruct the composition of the structure and interface for both cathode and anode, which can effectively restrain the oxidation decomposition of electrolyte as well as refrain the dissolve out of transition metals. The LiNi_0.8Co_0.1Mn_0.1O₂ (LNCM811)/graphite pouch cell with 1 wt% LIDFP in electrolyte delivers a discharge capacity retention of 91.3% at a high voltage of 4.4 V over 100 cycles, which is higher than the 82.0% of that without LIDFP additive. Additionally, the remaining capacity of LNCM811/C battery with 1 wt% LIDFP additive which is left at 60 °C for 14 days is 85.2%, and the recovery capacity is 93.3%. The LIDFP-containing electrolyte demonstrates a great application future for the LiBs operating under the high-voltage condition and high-temperature storage performance.     

Effect of soluble ash components on the viscosity of lignite-water mixtures

The removal of multivalent cations from lignite-water mixtures (LWM) was shown to lower mixture apparent viscosity by a factor of about 40, for example, at 100 s^?1 by reducing both the yield stress and plastic viscosity. The cations Ca⁺⁺, Mg⁺⁺, Al⁺⁺⁺, K⁺, and Na⁺, among others, were found to be present in the aqueous phase of the LWM in concentrations ranging from 546 ppm to 8 ppm. The primary anions present were CI^? and SO₄⁼. The degree to which the cations affected viscosity were of order trivalent > divalent > monovalent. The nature of the anion was found to be relatively unimportant. A process utilizing ion-exchange resins for removing multivalent cations to produce low viscosity lignite-water or coal-water mixtures is described.     

Compatibility of quaternary ammonium-based ionic liquid electrolytes with electrodes in lithium ion batteries

Electrochemical intercalation/deintercalation behavior of lithium into/from electrodes of lithium ion batteries was comparatively investigated in 1 mol/L LiClO₄ ethylene carbonate-diethyl carbonate (EC-DEC) electrolyte and a quaternary ammonium-based ionic liquid electrolyte. The natural graphite anode exhibited satisfactory electrochemical performance in the ionic liquid electrolyte containing 20 vol.% chloroethylenene carbonate (Cl-EC). This is attributed to the mild reduction of solvated Cl-EC molecules at the graphite/ionic electrolyte interface resulting in the formation of a thin and homogenous SEI on the graphite surface. However, rate capability of the graphite anode is poor due to the higher interfacial resistance than that obtained in 1 mol/L LiClO₄/EC-DEC organic electrolyte. Spinel LiMn₂O₄ cathode was also electrochemically cycled in the ionic electrolyte showing satisfactory capacity and reversibility. The ionic electrolyte system is thus promising for 4 V lithium ion batteries based on the concept of “greenness and safety”.     

Effect of small cation addition on the conductivity of quaternary ammonium ionic liquids

Several quaternary ammonium or lithium bis(trifluoromethane sulfone) imide (TFSI) salts were dissolved into N,N,N,N-hexyltrimethyl ammonium TFSI ionic liquid, and the conductivities of the resulting solutions were measured. Some asymmetric quaternary ammonium salts contributed to increase the conductivity of the solution, while cyano-containing quaternary ammonium and lithium salts decreased the conductivity. Based on the results of differential scanning calorimetry (DSC) measurements, such conductivity behaviors appeared to be related to the intrinsic miscibility of the ionic liquid solutions.     

Measurement and modeling of poly(vinyl acetate)–solvent viscosity mixtures

The viscosities of various poly(vinyl acetate) (PVAc)–solvent mixtures (PVAc–toluene, PVAc–benzene, and PVAc–cyclohexanone) were measured at different temperatures with a Haake viscometer. The required molecular weight of a commercial‐grade PVAc sample was measured with an Ubbelohde viscometer. The measured viscosities were correlated with a previously proposed viscosity model, and the model parameters were calculated. The results indicated the applicability of the model to the viscosity calculations of PVAc–solvent mixtures. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1244–1249, 2005     

Synthesis of LiFePO4/C cathode material from ferric oxide and organic lithium salts

LiFePO₄/C cathode material has been simply synthesized via a modified in situ solid-state reaction route using the raw materials of Fe₂O₃, NH₄H₂PO₄, Li₂C₂O₄ and lithium polyacrylate (PAALi). The sintering temperature of LiFePO₄/C precursor is studied by thermo-gravimetric (TG)/differential thermal analysis (DTA). The physical properties of LiFePO₄/C are then investigated through analysis using by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM) and the electrochemical properties are investigated by electrochemical impedance spectra (EIS), cyclic voltammogram (CV) and constant current charge/discharge test. The LiFePO₄/C composite with the particle size of ∼200 nm shows better discharge capacity (156.4 mAh g⁻¹) than bare LiFePO₄ (52.3 mAh g⁻¹) at 0.2 C due to the improved electronic conductivity which is demonstrated by EIS. The as-prepared LiFePO₄/C through this method also shows excellent high-rate characteristic and cycle performance. The initial discharge capacity of the sample is 120.5 mAh g⁻¹ and the capacity retention rate is 100.6% after 50 cycles at 5 C rate. The results prove that the using of organic lithium salts can obtain a high performance LiFePO₄/C composite.     

The transcendental role of lithium zirconates in the development of modern energy technologies

In the context of the current global environmental paradigm, lithium zirconate-based materials (LZOs) are of great technological interest in the reduction of the carbon footprint. Due to their exceptional mechanical, thermal and chemical stability, high lithium atom density and outstanding tritium release behavior, LZOs have been studied as tritium breeding ceramics for fusion technology. Besides, given that they can selectively and reversibly absorb CO₂ at high temperatures, LZOs could be used in the capture and industrial reuse of this gas. Moreover, in their most widespread use today, LZOs could be applied as nanocoatings on solid-state electrolytes and electrodes, constraining the formation of high resistive interfaces and slowing the evolution of dendrites, both in lithium-ion and solid-state batteries. Finally, there are some small contributions in the development of catalytic materials to produce biodiesel and air-hydrogen fuel cells based on LZOs, and also in the development of luminescent materials with photovoltaic applications. This article is the first review of the LZO system. It summarizes LZOs main applications and describes the latest advances in the technologies described above.     

A novel lithium intercalation compound based on the layered structure of lithium nitridonickelates Li3−2xNixN

New lithium nickel nitrides Li_3−2xNi_xN (0.20 ≤ x ≤ 0.60) have been prepared and investigated as negative electrode in the 0.85/0.02 V potential window. These materials are prepared from a Ni/Li₃N mixture at 700 °C under a nitrogen flow. Their structural characteristics as well as their electrochemical behaviour are investigated as a function of the nickel content. For the first time are reported here the electrochemical properties of a lithium intercalation compound based on a layered nitride structure. The Li_3−2xNi_xN compounds can be reversibly reduced and oxidized around 0.5 V versus Li/Li⁺ leading to specific capacities in the range 120-160 mAh/g depending on the nickel content and the C rate. Due to a large number of lithium vacancies, the structural stability provides an excellent capacity retention of the specific capacity upon cycling.     

Estimation of ion pair formation constants of lithium salts in mixtures of glymes and 1,4-dioxane

This paper presents data coming from ¹⁹F NMR spectroscopy and conductivity measurements used as two independent methods for the determination of ion pair formation constants. The studied systems were limited to lithium tetrafluoroborate and trifluoromethylsulfonate solutions in mixtures of 1,4-dioxane and glyme, diglyme or water. The systems containing glyme and diglyme have coordinating properties (donor and acceptor numbers) very similar to liquid poly(ethylene glycol) dimethyl ether and solid poly(ethylene oxide) and their composition can be tailored to have the dielectric constants similar to those of the polymeric systems. The obtained results are compared with the electrochemical and spectroscopic data found in the literature for liquid poly(ethylene glycol) dimethyl ether and solid poly(ethylene oxide). The main stress of the discussion is focused on ion-ion and ion-solvent interactions and the influence of the oligooxyethylene chain length on ionic pair formation. Additionally, on the basis of the electrochemical data for the dioxane-water solutions, the difference in behavior between water-free and water containing samples of similar polarity is discussed. To check the influence of the cation on ion pairing, a similar set of experiments was performed for tetraalkylamonium salts with identical anions.     

Characterization of solid polymer electrolytes based on poly(trimethylenecarbonate) and lithium tetrafluoroborate

The results of an investigation of a polymer electrolyte system based on the poly(trimethylene carbonate) host matrix, designated as p(TMC), with lithium tetrafluoroborate guest salt are described in this presentation. Electrolytes with lithium salt compositions with n between 3 and 80 (where n represents the number of (OCOCH₂CH₂CH₂O) units per lithium ion) were prepared by co-dissolution of salt and polymer in anhydrous tetrahydrofuran. The homogeneous solutions obtained by this procedure were evaporated, within a preparative glovebox and under a dry argon atmosphere, to form thin films of electrolyte.The solvent-free electrolyte films produced were obtained as very flexible, transparent, completely amorphous films and were characterized by measurements of total ionic conductivity, cyclic voltammetry, differential scanning calorimetry and thermogravimetry.     

油煤浆中溶剂的黏度与油煤浆黏度关系的研究

安庆芳烃萃取油是理想的煤液化起始溶剂的原料,常压,100℃以下用德国Haake旋转黏度仪测定了不同加氢次数安庆芳烃萃取油的黏度,神华煤液化循环溶剂的黏度及其相对应的干煤浓度为45%的煤浆黏度变化,提供了油煤浆中溶剂的黏度与油煤浆黏度关系的一种方法。     

无机盐对两性聚丙烯酰胺特性粘度的影响

用红外吸收光谱对两性聚丙烯酰胺结构进行了表征,表明分子链上丙烯酰胺(AM)、甲基丙烯酰氧乙基三甲基氯化铵(MADQUAT)和丙烯酰胺基甲基丙磺酸钠(NaAMPS)链节的存在。随后研究了NaCl、CaCl2浓度及pH值对不同阴阳离子度的聚合物特性粘度的影响。结果表明,AM-MADQUAT-NaAMPS共聚物特性粘度受CaCl2浓度影响较NaCl大,但总的来说耐盐性比单性离子聚合物好,且其特性粘度在很大范围内(除等电点附近)不受pH值的影响。     

Alkali-modified soy proteins: Effect of salts and disulfide bond cleavage on adhesion and viscosity

Soy protein isolates were treated with NaCl, Na₂SO₄, or Na₂SO₃ (disulfide bond-cleaving agent) at a pH of 10.0 and 50°C, and the effects of these salts on viscosity, adhesive strength on woods, and water resistance of the treated isolates were investigated. Viscosity and adhesive strength decreased with increasing concentrations of these salts. At a concentration of 0.1 M, these three salts reduced the viscosity of soy proteins with no significant adverse effects on adhesive strength and water resistance. Addition of 0.1 M NaCl, Na₂SO₄, or Na₂SO₃ reduced adhesive strength insignificantly from 1230 N to 1120, 1060, or 1013 N, respectively. The viscosity of protein isolate modified at pH 10.0 and 50°C in the absence of salts was >30,000 cP. Treatment with NaCl or Na₂SO₄ resulted in viscosity reductions to 6000 or 1050 cP, respectively. The Na₂SO₃ treatment yielded an isolate with the lowest viscosity of 110 cP and which retained adhesive and water-resistive properties. The water resistance of modified soy proteins with and without 0.1 M Na₂SO₃ treatment was not significantly different with 3.3 and 6.6% cumulative delaminations occurring after four water soaking cycles. Treatment with 0.1 M Na₂SO₃ resulted in an isolate with a 28% decrease in disulfide linkages.     

Beneficial effects of Mo on the electrochemical properties of tin as an anode material for lithium batteries

A simple, novel method for improving the electrochemical response of Sn in lithium cells is proposed that involves preparing Sn by a reduction procedure in the presence of Mo powders. Four different Mo_xSn_1 − x mixtures (0 < x < 0.26) were electrochemically tested and their structural and textural properties determined by using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical properties of the resulting composites in lithium cells were studied by galvanostatic, step potential electrochemical spectroscopy (SPES) and electrochemical impedance spectroscopy (EIS) measurements. The mixtures were found to consist of crystalline Sn and Mo; however, the presence of the latter element modified the Sn habit in two ways, namely, by significantly decreasing particle size and increasing the reactivity towards oxygen. Although Mo is inert towards lithium, it increased both the discharge capacity and the capacity retention of the electrode in relation to pure Sn. The improved interparticle connectivity, reduced electrolyte decomposition and decreased charge-transfer resistance observed in the Mo-containing samples appear to be beneficial effects of the addition of Mo.     

混合溶剂中SBS-g-PMMA接枝共聚物极限粘数的研究

本文研究了SBS－g－PMMA接枝共聚物在环己烷、甲苯、丙酮两两混合体系中极限粘数［η］随混合溶剂组成变化的关系。发现：混合溶剂中共聚物极限粘数是溶剂分别对共聚物各组份链段作用的共同贡献结果。因此，聚合物在混合溶剂中有可能存在分子链最为舒展的点，即为［η］极大值点。     

一种双离子梳状聚合物电解质的合成与性能研究

以端基含有烯丙基侧链含有氯甲基的不饱和聚醚 (UPEO)与苯乙烯 (St)共聚 ,得到以聚烯烃为主链、PEO为侧链、侧链挂载氯甲基的梳状聚合物 (CPPC) ,CPPC与亚硫酸锂反应 ,合成了一种新型单离子梳状聚合物电解质 (CPPL)。研究发现该梳状聚合物电解质的玻璃化温度 (θg)取决于苯乙烯的配比和磺化反应效率。对比研究了CPPL和CPPL复合LiClO4而成的双离子梳状聚合物电解质(CPPL2 )的θg、热稳定性、电化学窗口和电导率。测定结果表明 :CPPL和CPPL2的室温电导率分别为1.3× 10 -4s/cm和 7.8× 10 -4s/cm。     

Effect of electrochemical conditions on the performance worsening of Si/C composite anodes for lithium batteries

An effective and practical method for producing Si/C composites with 10-15 wt% of silicon nanoparticles embedded in a carbon matrix is developed. The procedure consists of mechanically mixing Si with pitch followed by dispersing in toluene and final heat-treatment between 1000 and 1100 °C. The homogeneity of the materials was confirmed by optical microscopy and HRTEM. X-ray photoelectron spectroscopy, X-ray diffraction and N₂ adsorption at 77 K were applied for determining the structural and textural characteristics. The lithium insertion/deinsertion performance was monitored from the galvanostatic charge-discharge characteristics using a Si/C-lithium two-electrode cell, and varying the electrochemical parameters. Silicon essentially enhances the electrode capacity (C_rev up to 600 mAh/g for 15% Si), the effect being proportional to the component content, but it affects the cycle life. The first cycle reversible capacity increases with the decrease of current density and discharge cut-off potential. However, using such conditions during cycling leads to rapid saturation of the silicon particles, from which the decay of the electrochemical performance starts. It is demonstrated that the evolution of reversible and irreversible capacity is strongly dependent on the kinetics of lithium diffusion in silicon particles and on the discharge potential cut-off.     

Prediction of electrolyte viscosity for aqueous and non-aqueous systems: Results from a molecular model based on ion solvation and a chemical physics framework

Electrolyte viscosity is a macroscopic property, although its foundation lies on molecular-scale interactions between solvent and ionic species. A comprehensive understanding of viscosity behavior with respect to solvent composition, salt concentration and temperature is only possible with correct interpretations of molecular interactions and related quantities. This work introduces a new methodology for predicting electrolyte viscosity under a wide range of conditions, based on molecular, physical, and chemical properties. The general formalism is universal for aqueous and non-aqueous systems alike. Although the immediate application of the resultant model is candidate electrolytes for lithium ion batteries, other applications abound in the areas of industrial fluids, biological systems, and other electrochemical systems whose performance characteristics are tied to viscosity. Viscosity predictions are compared to experimental data for a number of electrolytes, demonstrating exceptional accuracy of predictions over wide temperature ranges and broad ranges of salt concentration.