Phosphoryl‐Rich Flame‐Retardant Ions (FRIONs): Towards Safer Lithium‐Ion Batteries

The functionalized catecholate, tetraethyl (2,3‐dihydroxy‐1,4‐phenylene)bis(phosphonate) (H₂‐DPC), has been used to prepare a series of lithium salts Li[B(DPC)(oxalato)], Li[B(DPC)₂], Li[B(DPC)F₂], and Li[P(DPC)₃]. The phosphoryl‐rich character of these anions was designed to impart flame‐retardant properties for their use as potential flame‐retardant ions (FRIONs), additives, or replacements for other lithium salts for safer lithium‐ion batteries. The new materials were fully characterized, and the single‐crystal structures of Li[B(DPC)(oxalato)] and Li[P(DPC)₃] have been determined. Thermogravimetric analysis of the four lithium salts show that they are thermally stable up to around 200 °C. Pyrolysis combustion flow calorimetry reveals that these salts produce high char yields upon combustion.     

The Effects of CO2 Additional on Flame Characteristics in the CH4/N2/O2 Counterflow Diffusion Flame

The effects (chemical, thermal, transport, and radiative) of CO₂ added to the fuel side and oxidizer side on the flame temperature and the position of the flame front in a one-dimensional laminar counterflow diffusion flame of methane/N₂/O₂ were studied. Overall CO₂ resulted in a decrease in flame temperature whether on the fuel side or on the oxidizer side, with the negative effect being more obvious on the latter side. The prominent effects of CO₂ on the flame temperature were derived from its thermal properties on the fuel side and its radiative properties on the oxidizer side. The results also highlighted the differences in the four effects of CO₂ on the position of the flame front on different sides. In addition, an analysis of OH and H radicals and the heat release rate of the main reactions illustrated how CO₂ affects the flame temperature.     

Green and efficient extraction strategy to lithium isotope separation with double ionic liquids as the medium and ionic associated agent

The paper reported a green and efficient extraction strategy to lithium isotope separation. A 4-methyl-10-hydroxybenzoquinoline (ROH), hydrophobic ionic liquid—1,3-di(isooctyl)imidazolium hexafluorophosphate ([D(i-C₈)IM][PF₆]), and hydrophilic ionic liquid—1-butyl-3-methylimidazolium chloride (ILCl) were used as the chelating agent, extraction medium and ionic associated agent. Lithium ion (Li⁺) first reacted with ROH in strong alkali solution to produce a lithium complex anion. It then associated with IL⁺ to form the Li(RO)₂IL complex, which was rapidly extracted into the organic phase. Factors for effect on the lithium isotope separation were examined. To obtain high extraction efficiency, a saturated ROH in the [D(i-C₈)IM][PF₆] (0.3 mol l^?1), mixed aqueous solution containing 0.3 mol l^?1 lithium chloride, 1.6 mol l^?1 sodium hydroxide and 0.8 mol l^?1 ILCl and 3:1 were selected as the organic phase, aqueous phase and phase ratio (o/a). Under optimized conditions, the single-stage extraction efficiency was found to be 52 %. The saturated lithium concentration in the organic phase was up to 0.15 mol l^?1. The free energy change (ΔG), enthalpy change (ΔH) and entropy change (ΔS) of the extraction process were ?0.097 J mol^?1, ?14.70 J mol K^?1 and ?48.17 J mol^?1 K^?1, indicating a exothermic process. The partition coefficients of lithium will enhance with decrease of the temperature. Thus, a 25 °C of operating temperature was employed for total lithium isotope separation process. Lithium in Li(RO)₂IL was stripped by the sodium chloride of 5 mol l^?1 with a phase ratio (o/a) of 4. The lithium isotope exchange reaction in the interface between organic phase and aqueous phase reached the equilibrium within 1 min. The single-stage isotope separation factor of ⁷Li–⁶Li was up to 1.023 ± 0.002, indicating that ⁷Li was concentrated in organic phase and ⁶Li was concentrated in aqueous phase. All chemical reagents used can be well recycled. The extraction strategy offers green nature, low product cost, high efficiency and good application prospect to lithium isotope separation.     

Experimental and numerical simulation of effects of CO2/N2 concentration and initial temperature on combustion characteristics of biomass syngas

Biomass syngas is a form of renewable energy with very broad application prospects, and it has different combustion characteristics according to the fuel composition and processing technology of biomass syngas. The influence of combustion composition, diluent and temperature variation on combustion characteristics were studied in this paper. The FFCM-1 mechanism was used to investigate the combustion characteristics of CO/CH₄/H₂ under varied diluents CO₂/N₂ and temperature by using spherical expansion flame method and ANSYS CHEMKIN-PRO. The experimental laminar burning velocity was compared with the simulation results of FFCM-1 mechanism. The results reveal that the experimental data are in good agreement with the simulation results, which are somewhat different under the condition of rich fuel. The laminar burning velocity decreases significantly with the increase of diluent CO₂/N₂, with the effect of diluent CO₂ being more significant. The laminar burning velocity increase dramatically with the increase of initial temperature, and the adiabatic flame temperature also decreases with the increase of diluent. The reduction caused by diluent CO₂ is much larger than that caused by diluent N₂. The change of initial temperature also affects the adiabatic flame temperature, but the range of variation is not as pronounced as that of diluent. Not only was the interaction between the combustion characteristics of CO/CH₄/H₂ under different diluents and temperature changes explored in this paper, but the influence mechanism was also revealed in depth.     

A simplified synthesis of the hexamethylplatinate(IV) ion

Tetra-n-butylammonium hexachloroplatinate (IV) reacts with lithium methyl/lithium iodide in ether to give a solution containing lithium hexamethylplatinate (IV). With lithium methyl/lithium bromide in ether however, tetrabutylammonium hexamethylplatinate (IV) is precipitated together with lithium halides. Solid [Bu₄N)₂[Pt(Ch₃)₆] is stable under nitrogen at room temperature, but ether solutions of [Pt(Ch₃)₆]^2- decompose in a few minutes at room temperature in the absence of excess lithium methyl.     

球磨辅助高温固相法制备Li1.0Na0.2Ni0.13Co0.13Mn0.54O2正极材料及其性能

以乙酸盐(乙酸锂、乙酸钠、乙酸钴、乙酸镍、乙酸锰等)为原材料,采用球磨辅助高温固相法制备Li_(1.0)Na_(0.2)Ni_(0.13)Co_(0.13)Mn_(0.54)O_2正极材料。借助XRD、SEM等表征材料的结构和形貌,利用循环伏安、恒流充放电、交流阻抗等方法研究材料的电化学性能。结果表明,钠的掺杂导致颗粒表面光滑度降低,形成Na_(0.77)Mn O_(2.05)新相。0.05C活化过程中,掺钠样品和未掺钠样品首次放电比容量分别为258.4 m Ah·g~(-1)和215.8 m Ah·g~(-1),库伦效率分别为75.2%和72.8%;2C放电比容量分别为116.3 m Ah·g~(-1)和106.2 m Ah·g~(-1)。研究发现,掺钠可减小首次充放电过程的不可逆容量,提高容量保持率;改善倍率性能与容量恢复特性;降低SEI膜阻抗和电荷转移阻抗;掺钠后样品首次循环就可以基本完成Li_2Mn O_3组分向稳定结构的转化,而未掺杂的样品需要两次循环才能逐步完成该过程;XPS结果表明,掺钠样品中Ni~(2+)、Co~(3+)、Mn~(4+)所占比例明显提高,改善了样品的稳定性和电化学性能;循环200次后的XRD结果表明掺钠与未掺钠材料在脱嵌锂反应中的相变化过程基本一致,良好有序的层状结构遭到破坏是循环过程中容量衰减的主要原因。     

球磨辅助高温固相法制备Li1.0Na0.2Ni0.13Co0.13Mn0.54O2正极材料及其性能

以乙酸盐(乙酸锂、乙酸钠、乙酸钴、乙酸镍、乙酸锰等)为原材料,采用球磨辅助高温固相法制备Li_1.0Na_0.2Ni_0.13Co_0.13Mn_0.54O₂正极材料。借助XRD、SEM等表征材料的结构和形貌,利用循环伏安、恒流充放电、交流阻抗等方法研究材料的电化学性能。结果表明,钠的掺杂导致颗粒表面光滑度降低,形成Na_0.77MnO_2.05新相。0.05C活化过程中,掺钠样品和未掺钠样品首次放电比容量分别为258.4 mAh·g^-1和215.8 mAh·g^-1,库伦效率分别为75.2%和72.8%;2C放电比容量分别为116.3 mAh·g^-1和106.2 mAh·g^-1。研究发现,掺钠可减小首次充放电过程的不可逆容量,提高容量保持率;改善倍率性能与容量恢复特性;降低SEI膜阻抗和电荷转移阻抗;掺钠后样品首次循环就可以基本完成Li₂MnO₃组分向稳定结构的转化,而未掺杂的样品需要两次循环才能逐步完成该过程;XPS结果表明,掺钠样品中Ni²⁺、Co³⁺、Mn⁴⁺所占比例明显提高,改善了样品的稳定性和电化学性能;循环200次后的XRD结果表明掺钠与未掺钠材料在脱嵌锂反应中的相变化过程基本一致,良好有序的层状结构遭到破坏是循环过程中容量衰减的主要原因。     

Crystalline Intermediates during Polycondensation Reactions in the C–N–Cl System – The Paddle‐Wheel Molecule N(C6N7Cl2)3

Solid state metathesis reactions between cyanuric chloride and C–N–H or alkali metal–(B–)C–N compounds, respectively, were carried out in the temperature range between 150 °C to 500 °C, studying intermediate stages of reactions and targeting the formation of carbon nitride materials by elimination of HCl or alkali metal chlorides. Although cyanuric chloride was reacted with quite a number of different reaction partners such as melamine, cyanamide, lithium nitride, lithium or sodium carbodiimide, lithium nitridoborate or sodium dicyandiamide, always the same intermediate compounds appeared in the reactions mixtures. Colorless, needle‐shaped crystals of the tertiary amine N(C₃N₃Cl₂)₃ ( 1 ) were obtained at temperatures around 200–250 °C. Temperatures as high as 400 °C yielded yellow, plate‐like crystals of the heptazine compound C₆N₇Cl₃ ( 2 ). At even higher temperatures, the reaction products were of poorer crystallinity, but evidence of the formation of another crystalline intermediate was given by X‐ray powder diffraction and electron diffraction experiments. This third intermediate is assumed to be a tertiary amine, quite similar to 1 , however, having heptazine ligands instead of triazine ligands and is assigned with the formula N(C₆N₇Cl₂)₃ ( 3 ). Theoretical calculations were performed for the structures and the vibrational spectra of 1 and 3 . Theoretical calculations and a structure refinement based of X‐ray powder diffraction data yielded a plausible structural model for compound 3 .     

Block copolymers of polystyrene and poly(dimethyl siloxane). I. Synthesis and characterization

The block copolymers of the ABA type, poly(dimethyl siloxane-b-styrene-b-dimethyl siloxane), were synthesized by the anionic polymerization of styrene and cyclic siloxane monomer, hexamethyl cyclotrisiloxane (D₃) or octamethylcyclotetrasiloxane (D₄), with lithium or sodium biphenyl as initiator. The effect of initiator concentration, gegenion, and the polymerization temperature for styrene on molecular weight distribution (MWD) was investigated. Gel permeation chromatography (GPC) data show broader MWD of polystyrene prepared by sodium biphenyl in comparison to that produced by lithium biphenyl. The block copolymers have been characterized by infrared (IR) and nuclear magnetic resonance (NMR) spectra. The influence of dimethylsiloxy units on thermal stability of the copolymers has also been discussed.     

Synergistic effects of alkali metals in the alkylation of naphthalene and toluene with ethene in the ArH–alkali metal systems in THF (ArH – naphthalene,phenanthrene)

The use of mixtures of metallic lithium and sodium in the naphthalene–alkali metal systems in THF leads to a synergistic acceleration of the naphthalene alkylation with ethene at room temperature and atmospheric pressure. The greatest synergistic effect is observed at a Li:Na molar ratio of 2:1. Under these conditions, the overall conversion of naphthalene into alkylation products (linear 1-alkylnaphthalenes and their dihydro derivatives) attains 88% after 24 h (a (Li + Na):C₁₀H₈ ratio is 2:1). The use of mixtures of metallic lithium and potassium in such systems results, however, in a synergistic retardation of the alkylation process. The strongest retarding effect is observed at a Li:K molar ratio of 1:1. The efficiency of the toluene alkylation with ethene in the naphthalene–alkali metal systems in THF is also increased on the replacement of lithium or sodium by their mixtures. The best results are obtained at a Li:Na molar ratio of 1:3. With this Li:Na ratio, toluene is almost quantitatively converted into linear and α-branched higher monoalkylbenzenes (24 h, (Li + Na):C₁₀H₈ = 2:1). The rate of the naphthalene alkylation with ethene in the presence of toluene is enhanced as well on an introduction of mixtures of lithium and sodium into the system. However the maximum of the activity is shifted here towards higher lithium content (Li:Na = 1:1). A similar synergistic effect of lithium and sodium was found on studying the toluene alkylation with ethene in the phenanthrene–Li–Na systems in THF (a (Li + Na):phenanthrene ratio is 3:1). An addition of potassium to sodium also considerably increases the efficiency of the toluene and naphthalene alkylation with ethene in the naphthalene-based systems. The possible mechanism of the alkali metal synergism in the above-mentioned alkylation reactions is discussed.     

Low-Temperature Reactions of α-Bromopropanoyl Chloride with Lithium Derivative of Ethyl Acetate

The reaction of 2-bromopropanoyl chloride with lithium ethyl acetate generated in situ by the reaction of equimolar amounts of lithium diisopropylamide with ethyl acetate forms, depending on the conditions (temperature, time, reagent ratio), diethyl 2,2′-(3-methyloxirane-2,2-diyl)diacetate, 2,2-dibromo-N,N-diisopropylpropanamide, and ethyl (5-methyl-4-oxo-4,5-dihydrofuran-2-yl)acetate as minor by-products along with the expected acylation product ethyl 4-bromo-3-oxopentanoate. The reaction with 2 or 5 equiv of lithium ethyl acetate (–78°C → –20°C) gave, together with the mentioned α-bromo ester, ethyl (5-methyl-4-oxo-4,5-dihydrofuran-2-yl)acetate formed as a result of transformations of the adduct of the second LiCH₂CO₂Et molecule and ethyl-4-bromo-3-oxopentanoate. The reaction 2-bromopropanoyl chloride with sodium malonic ester involves acylation of enol form of the primary expected acylation product to afford dimethyl |2-bromo-1-[(2-bromopropanoyl)oxy]propylidene-malonate.

     

Synthesis and electrochemical properties of yttrium-doped LiMn<Subscript>0.98</Subscript>Y<Subscript>0.02</Subscript>O<Subscript>2</Subscript> for lithium secondary batteries

Yttrium-doped lithium manganese oxide (LiMn_0.98Y_0.02O₂) was prepared by ion exchange of lithium for sodium in NaMn_0.98Y_0.02O₂ precursors obtained by using rheological phase reaction method. This material had small particle size, which was composed of grain size of about 100 nm. Especially, LiMn_0.98Y_0.02O₂ delivered the initial discharge capacity of about 191 mA h g⁻¹ at room temperature when cycled between 2.0 and 4.4 V vs Li/Li⁺. Moreover, it showed an excellent cycling behavior, its specific capacity remained above 173 mA h g⁻¹ after 20 cycles, and the material did not transform into spinel structure during the electrochemical cycling according to the cyclic voltammograms and X-ray powder diffraction. The electrochemical results revealed that the doping of Y³⁺ improved the performance of LiMnO₂ considerably.     

Reversible lithium storage in Na2Li2Ti6O14 as anode for lithium ion batteries

The sodium lithium titanate with composition Na₂Li₂Ti₆O₁₄ has been synthesized by a sol–gel method. Thermogravimetric analysis and differential thermal analysis (TG–DTA) of the thermal decomposition process of the precursor and X-ray diffraction (XRD) data indicate the crystallization of sodium lithium titanate has occurred at about 600 °C. Electrochemical lithium insertion into Na₂Li₂Ti₆O₁₄ for lithium ion battery has been investigated for the first time. These results indicate the discharge and charge potential plateaus are about 1.3 V. The initial discharge capacity is much higher than the charge capacity and irreversible capacity exists in the voltage window 1–3 V. Subsequently, the discharge capacity decreases slowly, but the charge capacity increases slightly in the following cycles. After a few cycles, the specific capacity remains almost constant values and the sample exhibits the excellent retention of capacity on cycling.     

Über die Dihydrogenphosphide der Alkalimetalle,MPH2 mit M ≙ Li,Na, K,Rb und Cs

Dihydrogenphosphides of Alkali Metals, MPH₂ (M ? Li, Na, K, Rb, Cs) The dihydrogenphosphides from lithium to cesium were obtained by the reaction of PH₃ with the corresponding solutions of the metals or the metal amides in ammonia. The compounds were examined by X-ray, IR-spectroscopic, and thermochemical techniques. LiPH₂ is not stable at room temperature, while evolving PH₃ it decomposes to yellow products. NaPH₂ is a stable, white compound; above 393 K it decomposes associated with discolouring. KPH₂ and RbPH₂ exist in the region from 110 K to ～400 K in three crystalline forms. Its high-temperature modification is of the sodium chloride-type structure; a monoclinic deformation occurs with decreasing temperature. DSC-measurements revealed a further low temperature form. CsPH₂ crystallizes in the CsCl-type structure between 110 K and ～400 K.     

Study of quenching of S2 emission by addition of oxygen to a hydrogen flame in molecular emission cavity analysis

Interferences of oxygen on S₂ emission were measured for a hydrogen-oxgen flame in molecular emission cavity analysis and are discussed in terms of the emission intensities and temperatures in different regions of the flame. When a little oxygen is added to a hydrogen flame, S₂ emission is usually quenched. It also brings about a reduction in temperature in the lower region of the flame, where a cavity is introduced. However, in a “lower burnt hydrogen-oxygen flame”, in which hydrogen reacts instantly with added oxygen at the burner top, S₂ emission is not quenched by addition of oxygen, and the intensity and the flame temperature increase linearly with increasing oxygen flow-rate. Therefore, it is apparent that an increase in flame temperature is not responsible for the quenching. It is suggested that the existence of unburnt oxygen in the lower region of the flame can cause the quenching owing to the destruction of S₂ molecules to form sulphur-oxygen compounds.     

Synthesis of poly(methyl methacrylate) macromonomer

Anionic polymerization of methyl methacrylate (MMA) was carried out in tetrahydrofuran (THF) or THF/toluene mixture at ?78°C initiated by triphenylmethyl sodium or lithium as initiators. Highly syndiotactic PMMA of low polydispersity (M _w/m _n = 1.11–1.17) could be prepared with triphenylmethyl lithium in THF or THF/toluene mixture at ? 78°C. Moreover, PMMA macromonomer having one vinylbenzyl group per polymer chain was prepared by the couplings of living PMMA initiated by triphenylmethyl lithium with p-chloromethyl styrene (CMS) at ?78°C. The coupling reaction of living PMMA initiated by triphenylmethyl sodium with CMS was scarcely occurred.     

Effect of the lithium cation on the sorption and electrical properties of amphiphilic block copolymers and their composites

The use of lithium cation in composites of block copolymers [polyethylene‐b‐polyethylene oxide (PE‐b‐50%PEO and PE‐b‐80%PEO)] and their derivatives was tested as a modifier of the vapor sorption and impedance of these complexes. The block copolymer PE‐b‐80%PEO was modified by oxidation of its hydroxyl end group to both a carboxylic acid group (PE‐b‐80%PEO)CH₂COOH and its sodium salt (PE‐b‐80%PEO)CH₂COO^? Na⁺ for the purpose of improving its compatibility and performance as a matrix for composites. These modified copolymers were characterized by FTIR, DSC, and mass spectrometry. The sorption of water of these copolymers and their composites with lithium nitrate was also compared, as well as the electrical properties of their composites were measured by electrical impedance spectroscopy. For the composites obtained with PE‐b‐80%PEO and lithium nitrate, it was found that lithium cation plays an important role increasing the sorption rate, which is maximized for the PE‐b‐80%PEO + (21% lithium nitrate) composite. For the copolymers (PE‐b‐80%PEO)CH₂COOH and (PE‐b‐80%PEO)CH₂COO^? Na⁺ and their composites, the highest sorption rate was observed for salt in the following order: COO^? Na⁺ > COOH > OH. The PE‐b‐80%PEO + (21% lithium nitrate) composite behaves as a solid polymeric ionic conductor fitting the Williams–Landel–Ferry equation. However, both (PE‐b‐80% PEO)CH₂COOH and (PE‐b‐80%PEO)CH₂COO^? Na⁺ + (21% lithium nitrate) composites fitted the Variable Range Hopping equation, indicating a conductance trend with temperature governed by a thermally activated with energy of 0.482 and 0.524 eV and not by a relaxation process. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1809–1817, 2010     

Pseudo-Binary Phase Diagram of LiNH2-MH (M = Na,K) Eutectic Mixture

The hunt for a cleaner energy carrier leads us to consider a source that produces no toxic byproducts. One of the targeted alternatives in this approach is hydrogen energy, which, unfortunately, suffers from a lack of efficient storage media. Solid-state hydrogen absorption systems, such as lithium amide (LiNH₂) systems, may store up to 6.5 weight percent hydrogen. However, the temperature of hydrogenation and dehydrogenation is too high for practical use. Various molar ratios of LiNH₂ with sodium hydride (NaH) and potassium hydride (KH) have been explored in this paper. The temperature of hydrogenation for LiNH₂ combined with KH and NaH was found to be substantially lower than the temperature of individual LiNH₂. This lower temperature operation of both LiNH₂-NaH and LiNH₂-KH systems was investigated in depth, and the eutectic melting phenomenon was observed. Systematic thermal studies of this amide-hydride system in different compositions were carried out, which enabled the plotting of a pseudo-binary phase diagram. The occurrence of eutectic interaction increased atomic mobility, which resulted in the kinetic modification followed by an increase in the reactivity of two materials. For these eutectic compositions, i.e., 0.15LiNH₂-0.85NaH and 0.25LiNH₂-0.75KH, the lowest melting temperature was found to be 307 °C and 235 °C, respectively. Morphological studies were used to investigate and present the detailed mechanism linked with this phenomenon.     

Vacancy‐Controlled Na+ Superion Conduction in Na11Sn2PS12

Highly conductive solid electrolytes are crucial to the development of efficient all‐solid‐state batteries. Meanwhile, the ion conductivities of lithium solid electrolytes match those of liquid electrolytes used in commercial Li⁺ ion batteries. However, concerns about the future availability and the price of lithium made Na⁺ ion conductors come into the spotlight in recent years. Here we present the superionic conductor Na₁₁Sn₂PS₁₂, which possesses a room temperature Na⁺ conductivity close to 4 mS cm^?1, thus the highest value known to date for sulfide‐based solids. Structure determination based on synchrotron X‐ray powder diffraction data proves the existence of Na⁺ vacancies. As confirmed by bond valence site energy calculations, the vacancies interconnect ion migration pathways in a 3D manner, hence enabling high Na⁺ conductivity. The results indicate that sodium electrolytes are about to equal the performance of their lithium counterparts.     

Lithium and sodium yttrium ortho­silicate oxy­apatite,LiY9(SiO4)6O2 and NaY9(SiO4)6O2, at both 100 K and near room temperature

Lithium yttrium orthosilicate oxyapatite [lithium nonayttrium hexakis­(silicate) dioxide], LiY₉(SiO₄)₆O₂, crystallizes in the centrosymmetric space group P6₃/m at both 295 and 100 K. The structure closely resembles those of fluorine apatite and sodium yttrium orthosilicate oxyapatite [sodium nonayttrium hexakis­(silicate) dioxide], NaY₉(SiO₄)₆O₂, which was also investigated, at 270 and 100 K, in this study. There are two different crystallographic sites for the Y³⁺ ion, which are coordinated by seven and nine O atoms. One‐fourth of the nine‐coordinated site is occupied by Li or Na atoms, thus maintaining charge balance. The Si atom occupies a tetrahedral site. The two compounds show no symmetry change between room temperature and 100 K, and the alterations in structural parameters are small.