Recent progress of glass and glass-ceramics as solid electrolytes for lithium secondary batteries

In recent years many new glass-based solid electrolytes with high Li⁺ conductivity have been developed. In the present paper, we review the preparation and characterization of Li₂S-based oxysulfide glasses and sulfide glass-ceramics on the basis of two strategies of enhancing Li⁺ conductivity: the utilization of “mixed-anion effect” by combining sulfide and oxide anions, and the precipitation of superionic metastable crystals by careful heat-treatment of glasses. The superior Li⁺ conducting solid electrolytes with the highest conductivity and the lowest activation energy for conduction have been achieved in the Li₂S–P₂S₅ glass-ceramics. The use of these glass-ceramic solid electrolytes leads to the development of a bulk-type all solid-state lithium secondary battery with excellent cycling performance.     

Etude par R.P.E. d'electrolytes vitreux appartenant au systeme B2O3-Li2O-LiCl

An EPR study of fast Li⁺ ion vitreous conductors belonging to the B₂O₃-Li₂O-LiCl system has been carried out. The samples have been subjected to X-ray irradiation at room temperature. Two types of paramagnetic centers have been observed. The first one is the Cl₂^- species (Vk center) present in the part of the vitreous domain which corresponds to low LiCl concentrations, it vanishes when Li⁺ and Cl^- begin to order. The second one is of the B.O.H.C. type often present in alkali borate glasses. Its presence shows the similarity between the boron-oxygen network of the alkali borate glasses and of our samples containing alkali chloride.     

Etudes electrique et Raman des verres des systemes B2O3M2OM3PO4 (M=Li,Na)

New glasses with alkali carriers have been prepared in the system B₂O₃M₂OM₃PO₄ (M = Li, Na). The variation of the ionic conductivity has been discussed. Raman spectroscopy allows to characterize the behavior of the orthophosphate M₃PO₄ with respect to the boron-oxygen glass matrix.     

Effect of rapid quenching on electrical properties of lithium conductive glasses

A twin roller apparatus has been designed to be used in a controlled environment, so that even hydroscopic and oxidizable glasses may be prepared by rapid quenching. xLi₂O(1?x)P₂O₅ and xLi₂S(1?x)GeS₂ glasses have been prepared and their electrical conductivity measured as a function of temperature. The electrical characteristics of rapidly quenched and conventional glasses are compared in order to study the influence of the cooling rate. The results are quite different for oxide and sulfide glasses. Rapid quenching does not much affect oxide glasses whereas for sulfide glasses important decreases in activation energies and pre-exponential factors are observed.     

锂硼钒酸盐玻璃的11B核磁共振研究

用¹¹B连续波核磁共振谱研究了锂硼钒酸盐玻璃的结构,测量了BO₄,BO_3s和BO_3A各结构单元的比例。实验表明,锂硼钒酸盐玻璃中N₄的最大值近似为一常数,与V₂O₅的含量无关。Li₂O被V₂O₅和B₂O₃分享。并推测V₂O< 关键词：     

Etude par resonance paramagnetique electronique des verres du systeme B2O3-Na2O-Na3PO4

An EPR study of fast Na⁺ ion vitreous conductors of the system B₂O₃?Na₂O?Na₃PO₄ has been carried out. After X-ray irradiation two types of paramagnetic centers have been observed. The first one is of boron-oxygen hole center (B.O.H.C.) type and similar to that earlier observed for other alkali borate glasses. The second one is of PO₄^2? type. A simulation of its spectrum has been achieved and a defect model discussed.     

Factors affecting ionic conductivity in the lithium conducting glassy solid electrolytes

The electrical conductivity results of lithium borosilicate glasses with addition of Li₂SO₄ and LiCl have been critically analyzed. In general, it is observed that the factors viz. lithium fraction, f_Li and the number of non-bridging oxygens (NBOs) govern the ionic conductivity in the lithium conducting glasses. For the same f_Li, the presence of mixed formers in the glass gives higher conductivity compared to that of the glass with only one former. Thus the competitive network of glass in mixed former systems provides higher mobilities for lithium ions and hence high ionic conductivity. The addition of Li₂SO₄ and LiCl in the lithium borosilicate glasses gave enhancement in the conductivity. However, the mechanism of enhancement in conductivity is different in the two glass systems. The comparison of the result of binary, ternary and quaternary glass systems suggests that in general, the decrease in activation energy, increase in f_Li and increase in NBOs gives rise to enhancement in conductivity. For the same value of f_Li the higher conductivity is exhibited by glasses with lower value of K (K=SiO₂/B₂O₃). Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003.     

Lanthanum Oxide Effects on the Structure of Calcium Phosphate Glasses

Calcium phosphate glasses, in which part of calcium oxide was replaced by lanthanum oxide, were prepared by using the conventional melt quench method. The structures of xLa₂O₃ · (50-x)CaO · 50P₂O₅ (x = 0, 1, 3, 6, 12 mol%) samples were investigated by X-ray diffraction (XRD), Raman spectrum, Fourier transform infrared spectrum (FTIR), and differential scanning calorimetry (DSC). The results show that lanthanum oxide acts as network modifier in the network space of glass structure. The glass formation occurs at an O/P ratio of about 3.0–3.12. At larger values, the crystalline phases calcium pyrophosphate (Ca₂P₂O₇) and calcium lanthanum phosphate [Ca₉La(PO₄)₇] are detected in the samples. Raman and FTIR spectra indicate that the structure of lanthanum-free sample is chain P–O–P bond metaphosphate–based Q² units. Glass structure will change to Q² and Q¹ units when the lanthanum oxide content is less then 6 mol%. When lanthanum oxide content increases to 9 and 12 mol% more nonbridging oxygen in the glass, resulting in the depolymerization of the phosphate network, the network of glass transforms to Q², Q¹, and Q⁰ units mixture. Based upon DSC results, T_g slightly decreases because of the depolymerization of microstructure. Endothermal peak of DSC curves indicate that crystal phases separate out from vitreous body with the addition of lanthanum oxide content.     

Discovery of a linear relationship between the glass transition temperature of oxide glasses and the quadrupole splitting of the Fe3+ substituted for the individual network—forming cations (NWF)

⁵⁷Fe-Mössbauer and DTA study of several oxide glasses has revealed that there exists a linear relationship between Tg(glass transition temperature) and δ (quadrupole splitting) of Fe³⁺, which is substituted for individual NWF(network former), e.g., V⁵⁺, Ti¹⁺, Te¹⁺, Al³⁺, Ca³⁺ and B(III). The linear relationship named “Tg-δ rule” is expressed by Tg=aδ+b, which indicates that Tg of oxide glasses is closely correlated to the asymmetry or local distortion of NWF-oxygen polyhedra. The “Tg-δ rule” also holds for the γ-ray irradiated tellurite glasses and for the glass-ceramics of calcium aluminate.     

Diffusion of sodium ions in borosilicate glasses by molecular dynamics method

Molecular dynamics simulations of borosilicate glasses with different sodium oxide content has been carried out. The generated structure indicates that the major number of oxygen atoms introduced as Na₂O consumes in the borate network to convert the BO₃ triangles to BO₄ tetrahedra. The formation of nonbridging oxygen ions in the silica site occurs during the formation of BO₄ tetrahedra with low rate. At higher concentrations of Na₂O, the NBO's increases abruptly. The self diffusion of sodium ions depends essentially on the temperature, composition (number of Na⁺ ions) and the rate of cooling. The phase separation mechanism in borosilicate glasses can be detected by MD simulation since the environment of the B–O, Si–O and B–O–Si can be easily reached.     

Quartz crystal microbalance measurements of O/Ti and CO/Ti atom ratios on very thin Ti films

The adsorption of O₂ and CO on Ti films with thicknesses in the range 0–200 Å was investigated by quartz crystal microbalance (QCM) measurements. The O/Ti and CO/Ti ratios in the limit of zero film thickness was determined to be 1.5 and 0.5 respectively using the film thickness as a parameter. This result suggests that the oxide formed is Ti₂O₃. The Ti + O₂ results are discussed in a model where the thinnest metal films are assumed to consist of metal islands. From the model an “oxidation depth” of ≈10 Å is estimated.     

Synthesis of LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> by molten salt technique

Lithium manganese oxide powders have been successfully prepared by a molten salt synthesis using eutectic mixture of LiCl and MnO₂ salt at 900 °C. The synthesis was performed in open atmosphere. The crystalline powders were characterized for their phase identification using X-ray diffraction analysis. The physicochemical properties of the lithium manganese oxide powders are investigated by thermal analysis (thermo gravimetric analysis/ differential thermal analysis), Fourier transform infrared spectroscopy, Raman spectroscopy, atomic absorption spectroscopy, electron spin resonance spectroscopy, and scanning electron microscopy. This work shows the feasibility for obtaining lithium manganese oxide at low-temperature molten salt flux method.     

分子动力学模拟不同组分下CaO-Al2O3-SiO2系玻璃微观结构的转变

采用分子动力学模拟的方法研究了CaO-Al₂O₃-SiO₂系玻璃的微观结构，发现Ca/Al=1/2时CaO-Al₂O₃-SiO₂系玻璃(网硅酸盐体系)并不像传统理论认为的那样是一个完整的三维网络，而是存在一定量的非桥氧，从而从理论上进一步证实了Stebins等人的实验结果.同时也发现不同的Ca/Al比对Si和Al键接方式产生重要影响，在Ca/Al>1/2时，Al比Si容易成为网络的中间体，其首先插入网络体中间；在Ca/Al<1/2时，Si比Al容易成为网络中间体.虽然在能量上Al—O—Si占有扰势，但当Ca/Al从大于1/2变化到小于1/2时，仍有部分Al—O—Si转变成Al—O—Al和Si—O—Si，丰富了Al自回避规则的内容. 关键词： 2O₃-SiO₂')" href="#">CaO-Al₂O₃-SiO₂ 玻璃 微观结构 分子动力学     

Modelling the size of red-colouring copper nanoclusters in archaeological glass beads

The origin of a red colour in ancient soda-lime glasses has been attributed either to the presence of both copper clusters and cuprous oxide or to copper alone. As a contribution to this question, a non-destructive X-ray absorption study at the [ _Cu]K-edge was undertaken on the red layer from a singular “rosette”-type archaeological glass bead dated as pre-XVII century. On comparing with data collected from metallic copper and the mineral cuprite, cubic Cu₂O, XANES spectra of the red glass are identical to the first. Theoretical modelling of Cu 1s XANES spectra was undertaken using the FEFF code based on a multiple scattering formalism. A hypothetical tetragonal structure was simulated for Cu₂O in order to remove the constraints arising from linear O–Cu–O bonds, unstable within the silica glass matrix, and an ideal body-centred array was considered on the basis of real metallic Cu–Cu distances in the metal. Calculations were performed for atom clusters of variable size within real and hypothetical structures. A spherical cluster of about 5 Å radius, capped by 24 copper atoms already provides a calculated Cu 1s XANES spectrum that compares well with data collected from the red glass. Post-edge details are noted in relation to the oxide, considering ionic states and effective valences of copper. The possibility of estimating the size of copper clusters through simulated structures is discussed.     

Structure investigations of ultraphosphate glasses with some water content

Phosphorus pentoxide (P₂O₅) is a good glass-forming oxide, but highly hygroscopic. Therefore, glasses of the binary phosphate systems have to be melted in a closed system. Glasses in the systems P₂O₅–H₂O and P₂O₅–D₂O (up to 15 mol% H₂O or D₂O) and glasses with low metal oxide content (up to 12 mol%) were melted. The water as well as the deuterium oxide (D₂O) clearly modifies the glass structure. They act very similar to the metal oxides.     

β-irradiation effect in aluminoborosilicate glasses: The role of <Emphasis Type="Italic">RE</Emphasis> codoping (<Emphasis Type="Italic">RE</Emphasis> = Sm,Gd)

The effect of Sm and Gd codoping on the structural modifications of β-irradiated aluminoborosilicate glasses has been studied by electron paramagnetic resonance (EPR) and Raman spectroscopy. The EPR spectra showed that the relative amount of Gd³⁺ ions occupying network former positions (Gd_[n.f.]³⁺) follows a nonlinear behavior as a function of the Sm/Gd ratio. This suggests that codoping favors the occupation by Gd³⁺ ions of the network former positions rather than the modifier positions in aluminoborosilicate glasses. The appearance of a superhyperfine structure of EPR lines attributed to boron-oxygen hole centers (BOHC) with increasing Sm/Gd ratio was observed. This suggests that Gd³⁺ ions are diluted in the vicinity of the BOHC defects. The concentration of defects created by irradiation reveals a nonlinear dependence on Sm and Gd codoping for the lowest irradiation dose (10⁵ Gy). Therefore, codoping also affects the defect creation processes at least at the lowest irradiation dose. Raman spectroscopy measurements suggest that the irradiation-induced structural changes vary nonlinearly with the Sm/Gd ratio. In fact, the shift of the Si-O-Si bending vibration modes reveals a clear minimum for samples containing equal amounts of Sm and Gd (1: 1) in the investigated glasses. The text was submitted by the authors in English.     

Influences on power performances of metal oxide additives for LiFePO4 electrodes

Metal oxide additives are added into LiFePO₄ electrodes attempting to improve cell power performances. Electrochemical performances are tested with 5 wt% different sizes of neutral alumina, nano Al₂O₃, and nano MgO individually comparing with those with 5 wt% more active LiFePO₄ and acetylene black. The polarization between charge and discharge plateaus is reduced not only by adding more conductive acetylene black, but also by adding all these insulated metal oxide additives. Adding natural alumina and nano MgO can significantly increase rate capacities. This might be because of their “lithium ion saver” effect.     

Mössbauer spectroscopic study on soda-vanadate glass system containing iron

Room temperature Mössbauer spectra of xFe₂O₃: (1-x) (Na₂O: 2V₂O₅) glass system showed that Fe³+ are present at both tetrahedral-“network modifying” and octahedral-“network modifying” sites. A Zeeman hyperfine splitting is also observed for x=0.225 along with a doublet, whose internal magnetic field (?518±5 KOe) and isomer shift are found comparable to that of α-Fe₂O₃.     

Lack of oxygen substitution in the chevrel compound Mo6S8

We present results from x-ray powder diffraction and lithium intercalation cells on samples of nominal composition “Cu₂Mo₆S₆O₂” and “Mo₆S₆O₂”. Our results show that it is not possible to prepare these materials with any significant fraction of the sulfur substituted by oxygen as claimed by Umarji et al.¹ Instead, the high temperature (1250°C) products from starting materials of CuO, Cu, S, MoO₂ and/or Mo are MoO₂, Mo and Cu_yMo₆S₈ with y>2.     

Infrared spectra of double-alkali silicate glasses

Infrared reflection spectra have been taken of bisilicate glasses in which one alkali oxide (Na₂O, K₂O) is gradually replaced by another while their total content is kept constant, and the electrical conductivity and density, of these glasses have been determined. The spectra of single-alkali glasses containing 16–20% of alkali and whose structure, according to some authors, is similar to that of bisilicate glasses, are also included. The main characteristic features of the spectra of double-alkali glasses do not confirm this assumption, but indicate that their structure approximates that of single-alkali glasses; nevertheless, the parts composing the microheterogeneous structure have an altered composition as compared with that of single-alkali glasses. Electrical conductivity passes through a minimum for all three combinations of the alkali oxides, while density passes through a weak maximum in the case of sodium-potassium glasses only.