Oxysulfide Glasses Research Articles

Incorporation of Lithium Ultra-Phosphate into Li-Si-S Glass Compositions

Development of a solid electrolyte in solid-state batteries has been of increasing focus in recent years. A promising contender is glassy solid electrolytes due to their tunable properties and ease of synthesis. Mixed oxy-sulfide glasses (MOS) glassy solid electrolytes (GSEs) have been shown to exhibit high electrochemical stability, high ionic conductivity, and easily synthesized. In this MOS glass series, we are substituting Li0.67PO2.83 with SiS2 to form the glass series of 0.58 Li2S + 0.378 SiS2 + 0.042 Li0.67PO2.83. Differential scanning calorimetry (DSC) was used to determine the glass and crystallization temperatures. Electrical impedance spectroscopy (EIS) was taken to understand and measure the Li+ ion conductivity. To identify the structure in these glasses, we utilized Fourier transform infrared (FTIR) and Raman Spectroscopy. The results show that through incorporation of oxides into sulfides there is an improvement in the properties of these materials.

Effect of Oxygen Content on Free-Sulfur Defects in Sodium Phosphosilicate Oxy-Sulfide Glasses

Sodium glassy solid electrolytes (GSEs) are an attractive option for the future of grid-scale energy storage. This is primarily because sodium is far more abundant than lithium, driving down material cost and allowing for large-scale implementation. Additionally, GSEs do not pose the same risk of fire as organic liquid electrolytes that are found in most batteries on the market today. However, the presence of free-sulfur defects in these glasses has been shown to make them cathodically unstable and undermine their usefulness as GSEs. Previous work suggests that increased oxygen content contributes to an increase in free-sulfur defects in these glasses, but the mechanism is unknown. To investigate further, samples of NaPSiSO from the series (1-y)Na2S + y{(1-z)[(1-a)SiS2 + aPS5/2] + zNaPO3} were synthesized with oxygen content (O/[O+S]) ranging from 0.0 to 0.3 while glass former ratio and R-value were held constant. These glasses were characterized using Raman spectroscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, and x-ray photoelectron spectroscopy to investigate the mechanism of formation for free-sulfur defects.

(Invited) Designing a Safe and Sustainable Future: Sodium Ion and All-Solid-State Batteries

In this presentation, I will present the key challenges confronting all-solid sodium batteries, and how soft organic redox materials could enable intimate interfacial contact with solid electrolytes under low operating pressure. Additionally, we developed an oxysulfide glass electrolyte that forms a thin, dense, self-limiting interphase against Na metal and exhibits a fully dense glass microstructure. I will also discuss the role of Na-ion electrolyte additives for stabilizing hard carbon anodes.

Influence of oxygen distribution on the Li-ion conductivity in oxy-sulfide glasses - taking a closer look.

Lithium thiophosphates are a promising class of solid electrolyte (SE) materials for all-solid-state batteries (ASSBs) due to their high Li-ion conductivity. Yet, the practical application of lithium thiophosphates is hindered by their chemical instability, which remains a prevalent challenge in the field. Oxygen substitution has been discussed in the literature as a promising strategy to enhance stability. Nevertheless, the lack of understanding of the role of synthesis strategy on the resulting structure-property relationship makes it difficult to predict and control the material's behaviour, limiting our ability to fully utilize oxygen substitution as a viable solution. Here, we show that not only the total oxygen content but also the oxygen distribution within the material affects the ion conductivity. By carefully analysing the local structure of oxy-sulfide glasses, we find that few highly oxygenated structural units like [PO4]3- and [PO3S]3- are more detrimental to the ionic conductivity than a larger amount of less substituted units like [POS3]3-. Further, we demonstrate how the oxygen distribution is connected to the synthesis in high-energy ball milling by comparing two different sets of precursor materials. The results may explain the deviations in the past literature. The findings should be transferable to other Li-thiophosphate materials and enable more directed design of new materials.

Improved Thermal Stability of Oxysulfide Glassy Solid-State Electrolytes

In this study, the crystallization kinetics of (oxy)sulfide 70Li2S·(30-x)P2S5·xP2O5 (x = 0, 2, 5) solid-state electrolytes are reported. It was found that 5 mol% P2O5 glass co-former slowed the crystallization rate of the Li7P3S11−x/4Ox/4 ceramic phase by a factor of 10. After 10 min at 230 °C, a 70Li2S·30P2S5 sulfide glass was 92% devitrified whereas a 70Li2S·25P2S5·5P2O5 oxysulfide glass was only 8% devitrified. The improved thermal stability of oxysulfide glasses was then utilized to demonstrate the fabrication of a standalone, reinforced SSE separator by hot pressing. More importantly, it was recognized that the microstructure of 70Li2S·25P2S5·5P2O5 oxysulfide SSE separators could be modified by hot pressing without changing ionic conductivity. This result was achieved because the precipitation of a superionically conductive Li7P3S11−x/4Ox/4 ceramic phase was limited. A study was then conducted to determine what effect microstructure has on the susceptibility of SSE separators to shorting by lithium metal penetration. Hot-pressed separators were found to be more susceptible to shorting than cold-pressed separators. X-ray Computer Tomography (XCT) of post-mortem samples showed that hot-pressed samples failed by transverse microcrack pathways, which underscores the importance of low defect density in dense SSE separators.

Local-Structure Analysis of Li Oxy-Sulfide Glass-Ceramic Solid Electrolytes

In the global quest to tackle climate change and the promotion of sustainable energy sources, energy storage has become an important aspect and consequently has attracted great research attention. Solid state batteries promise increased energy density and safety in comparison to current commercial Li-ion batteries[1]. Fast ion conducting solid electrolyte materials are an essential part of solid-state batteries. The study of suitable materials and the understanding of the conduction mechanisms is therefore of high importance.Sulfide and thiophosphate glasses have been identified as promising candidates as fast ion conducting materials and great progress has been made since the first studies in 1980[2]. One drawback of these materials is their sensitivity against humidity and instability on exposure to air. Recently, it was demonstrated that the doping of thiophosphate glasses with oxygen has a positive effect on the ion conductivity[2]. Furthermore, an improvement of the chemical and physical stability of these doped glasses could be achieved. The combination of these two effects renders oxygen doping a promising strategy. However, very little is known so far about the local structure of the doped glasses and glass ceramics, yet this information is crucial to enable purposeful development and further improvement of these materials.Hence, we have studied the local structure of oxy-sulfide glasses as well as their structural evolution and crystallization behavior with increasing temperature. Additionally, the influence of the starting materials was evaluated by comparing materials from two different set of starting materials using the same synthesis route. Oxy-sulfide glasses of the composition Li3POxS4-x with 0 ≤ x ≤ 1.2 were synthesized by ball milling appropriate amounts of either Li2O, Li2S and P2S5, or Li3PS4 and Li3PO4. Temperature dependent x-ray powder diffraction and pair distribution function (PDF) analysis, supported by Raman spectroscopy and other characterization techniques, was then used to identify crystal phases and structural moieties. Subsequently, impedance measurements were carried out to be able to link microstructure to ionic conductivity.[1] Tan, D.H.S., Banerjee, A., Chen, Z. et al. From nanoscale interface characterization to sustainable energy storage using all-solid-state batteries. Nat. Nanotechnol. 15, 170–180 (2020). https://doi.org/10.1038/s41565-020-0657-x [2] Martin, S.W. Chapter 14: Glass and Glass-Ceramic Sulfide and Oxy-Sulfide Solid Electrolytes. Handbook of Solid State Batteries, pp. 433-501 (2015) https://doi.org/10.1142/9789814651905_0014 Figure 1

An electrochemically stable homogeneous glassy electrolyte formed at room temperature for all-solid-state sodium batteries

All-solid-state sodium batteries (ASSSBs) are promising candidates for grid-scale energy storage. However, there are no commercialized ASSSBs yet, in part due to the lack of a low-cost, simple-to-fabricate solid electrolyte (SE) with electrochemical stability towards Na metal. In this work, we report a family of oxysulfide glass SEs (Na3PS4−xOx, where 0 < x ≤ 0.60) that not only exhibit the highest critical current density among all Na-ion conducting sulfide-based SEs, but also enable high-performance ambient-temperature sodium-sulfur batteries. By forming bridging oxygen units, the Na3PS4−xOx SEs undergo pressure-induced sintering at room temperature, resulting in a fully homogeneous glass structure with robust mechanical properties. Furthermore, the self-passivating solid electrolyte interphase at the Na|SE interface is critical for interface stabilization and reversible Na plating and stripping. The new structural and compositional design strategies presented here provide a new paradigm in the development of safe, low-cost, energy-dense, and long-lifetime ASSSBs.

O‐Tailored Microstructure‐Engineered Interface toward Advanced Room Temperature All‐Solid‐State Na Batteries

AbstractThe severe parasitic interface reaction and dendrite growth retard the practical applications of all‐solid‐state (ASS) Na batteries with sulfide solid electrolytes (SEs). Here, a novel composite SE is proposed, with a high ionic conductivity, composed of Na3SbS4 (NSS) and oxysulfide glass. The study reveals that the P2S7‐aOa and PS4‐aOa units in oxysulfide play various roles: The former is deoxidized to release free O ions, which reacts with the anode via migrating to form oxides, favoring an improved interface stability. The latter is highly stable upon cycling, thereby maintaining an ion transport network. Meanwhile, NSS acts as a dendrite predator via reacting with penetrated Na. These advantages enable the resulting ASS Na battery with superior long‐term cycling performance at a high current density at room temperature, one of the best results so far. This discovery sheds light on innovative advanced SE materials through an oxysulfide‐based composite design.

Effects of oxides on optical absorption and homogeneity of GeS2-­Sb2S3-based glass

ABSTRACT We investigated the effects of oxygen impurities on the optical absorption, glass structure, and homogeneity of a sulfide glass that is a potential candidate for use as an infrared-transmitting material. We prepared glasses based on the pseudo-binary GeS2-Sb2S3 system by a conventional method using metals and sulfur as raw materials in an evacuated silica glass ampoule. The oxygen impurity content according to oxygen analysis was 0.034 mass% (340 ppm) for 20GeS2·80SbS3/2 glass. The oxygen impurities were distributed as oxides bonded to Ge and Sb with a distribution constant, although most of the oxygen was bonded to Ge. In addition, oxysulfide glasses were prepared by substituting GeO2 or Sb2O3 for the corresponding sulfides. In this case, the oxygen of the added oxides bonded mainly to Ge in the glasses. When more than 2 mol% of the oxides was substituted for the corresponding sulfides in the 20GeS2·80SbS3/2 glass, the glass became translucent or opaque. Microscopy observation revealed that droplet phases with diameters of 2 to 4 µm were precipitated. These phases were rich in germanium and oxygen. The inhomogeneity is induced by the addition of oxides to the glasses, particularly, in those with a large fraction of Sb2S3 in the composition.

New Amorphous Oxy-Sulfide Solid Electrolyte Material: Anion Exchange, Electrochemical Properties, and Lithium Dendrite Suppression via In Situ Interfacial Modification.

Glassy sulfide materials have been considered as promising candidates for solid-state electrolytes (SSEs) in lithium and sodium metal (LM and SM) batteries. While much of the current research on lithium glassy SSEs (GSSEs) has focused on the pure sulfide binary Li2S + P2S5 system, we have expanded these efforts by examining mixed-glass-former (MGF) compositions which have mixtures of glass formers, such as P and Si, which allow melt-quenching synthesis under ambient pressure and therefore the use of grain-boundary-free SSEs. We have doped these MGF compositions with oxygen to improve the chemical, electrochemical, and thermal properties of these glasses. In this work, we report on the short-range order (SRO), namely atomic-level, structures of Li2S + SiS2 + P2O5 MGF mixed oxy-sulfide glasses and, for the first time, study the critical current density (CCD) of these Si-doped oxy-sulfide GSSEs in LM symmetric cells. The samples were synthesized by planetary ball milling (PBM), and it was observed that a certain minimum milling time was necessary to achieve a final SRO structure. To address the short-circuiting lithium dendrite (LD) problems that were observed in these GSSEs, we demonstrate a simple and novel strategy for these Si-doped oxy-sulfide GSSEs to engineer the LM-GSSE interface by forming an in situ interlayer via heat treatment. Stable cycling to ∼1200 h at a capacity of 2 mAh·cm-2 per discharge/charge cycle under a current density of 1 mA·cm-2 is achieved. These results indicate that these MGF oxy-sulfide GSSEs combined with an optimized interfacial modification may find use in LM, and by extrapolation, SM, batteries.

Ionic conductivity and thermal stability of Li2O–Li2S–P2S5 oxysulfide glass

Sulfide-based solid electrolytes exhibit high ionic conductivities of more than 10−4 S cm−1 at room temperature. However, sulfide electrolytes have a major disadvantage because they are hygroscopic. To reduce costs and develop practical all-solid-state batteries, it is imperative to enhance their chemical stability in air. In this study, Li2O is added to 75Li2S·25P2S5 glasses to improve their chemical stability to moisture in air, and (75 − x)Li2S·25P2S5·xLi2O samples are synthesized. The effects of the addition of Li2O on the electrical properties and thermal behavior of 75Li2S·25P2S5 glasses are examined. With an increase in the Li2O content, the crystallization temperature of 75Li2S·25P2S5 glasses shifts to the high-temperature side, and the glass phase stabilizes over a wide temperature range. Specifically, the substitution of Li2O with Li2S enhances the thermal stability of glasses. This is attributed to the change in the precipitated crystalline phase, β-Li3PS4 (x = 0, 5) → thio-LISICON III Li3.2P0.96S4 (x = 10, 15). In addition, the (75 − x)Li2S·25P2S5·xLi2O glass ceramics for x = 15 exhibit higher conductivity than pristine glasses because of the thio-LISICON III Li3.2P0.96S4 crystalline phase. Thus, the addition of more than 10 mol% of Li2O ensures a good balance between thermal stability, atmospheric stability, and conductivity.

Glass formation and structural analysis of Na4P2S7-xOx, 0 ≤ x ≤ 7 sodium oxy-thiophosphate glasses

The short-range order (SRO) structures of glasses in the Na4P2S7-xOx, 0 ≤ x ≤ 7 system were investigated on samples prepared by planetary ball milling (PBM). Like other glasses prepared by PBM, the glassy nature of the prepared materials was confirmed by x-ray diffraction (XRD) showing that they were structurally amorphous and by differential scanning calorimetry (DSC) showing that each composition exhibited a reproducible glass transition temperature (Tg). The SRO structure of these glasses were determined using a combination of Raman, Fourier Transform Infrared (FT-IR), and 31P Magic Angle Spinning NMR (MAS NMR) spectroscopies to investigate how oxygen and sulfur are bonded in the various SRO structural units that were found in these glasses. The three spectroscopic techniques gave further evidence that the resulting glasses were completely reacted from their starting polycrystalline materials Na2S, P2S5 and P2O5. It was found that significant disproportionation reactions occur in these compositions in which the original as-batched and expected pyro-phosphate SRO units, P1 = 2 Na/P, for x = 0 undergo a transformation to form charge compensated amounts of ortho-phosphate (P0, 3 Na/P) and meta-phosphate (P2, 1 Na/P) SRO structures with increasing x such that there is a conservation of Na+ charge, on average 2Na/P. In this nomenclature, the superscript is the total number of bridging sulfurs (BSs) and bridging oxygens (BOs), three minus the superscript is the number of Na per P, and four minus the superscript is the total number of non-bridging sulfurs (NBSs) and non-bridging oxygens (NBOs) on each of the SRO units. As seen in earlier work on other mixed oxy-sulfide (MOS) glass forming systems, the stronger Lewis base O=, compared to S=, is found to preferentially form BOs in the form of P2 units by bonding to the stronger Lewis acid P+5, compared to Na+. This leaves the weaker Lewis base S= to bond to the weaker Lewis acid, Na+, in the form of NBSs on the charge compensation required P0 groups. Using both charge balance and quantitative 31P MAS NMR measurements, a complete composition map of all of the SRO structures present in these glasses has been determined.

Thermal stability and band gap study of heavy metal oxy-sulfide glass system

Novel oxy-sulfide glass system xPbS-(73 − x) Bi2O3–27B2O3 with 6.06 ≤ x ≤ 36.35 named lead sulfide bismuth borate (LSBB) was prepared using normal melt and quench-casting technique. Phase transition temperatures tg, tx, tpi, and tl were noted from the DTA curves. Glass transition temperature tg varied from 306 ± 2 to 336 ± 2 °C and the onset of crystallization temperatures tx was between 331 ± 2 and 402 ± 2 °C. The glasses melted in the range 523 ± 2 to 597 ± 2 °C. The ratio tg/tl showed that compositions reported conform to the two-third law of glass formation. Hruby’s coefficient Hr witnessed the thermal stability of the system and that LSBB4 was most stable and glass formability factor kgl showed that composition LSBB1–LSBB6 can easily corroborate vitreous state. The direct band gap energy varied from 1.56 to 3.07 eV, while indirect band gap energy for the fundamental absorption edge was 0.21–1.31 eV. Absorption edges obeyed Urbach rule. A broad range of band tailing was exhibited confirming amorphous state of the system.

Ion-implanted Ti-doped chalcogenide glass waveguide as a candidate for tunable lasers

A titanium-doped gallium lanthanum oxysulfide glass waveguide was fabricated by double proton implantation. The waveguide does not exhibit tunneling effect, which is consistent with our design. The refractive index distribution of the waveguide was reconstructed, and the propagation loss was measured to be 0.5 dB/cm, caused by the ion implantation. Based on Raman analyses, we conclude that the glass matrix expansion due to nuclear damage causes optical barrier formation. Little change in the guiding layer and low propagation loss present that a Ti-doped chalcogenide glass waveguide may be a candidate for tunable lasers and has the possibility of taking the place of versatile but expensive Ti:sapphire lasers.

Application of swift and heavy ion implantation to the formation of chalcogenide glass optical waveguides

We demonstrate the application of swift and heavy ion implantation to generate optical waveguides in amorphous materials. Gallium lanthanum sulfide (GLS) and gallium lanthanum oxysulfide (GLSO) glass waveguides are fabricated using Ar implantation at 60MeV and 2×1012ions/cm2. A “well” region with increased refractive index (0.1% for GLS and 0.3% for GLSO) is formed near the surface of the glass based on the electronic energy deposition; a “barrier” layer with decreased refractive index is formed inside the glass due to the nuclear energy deposition. As a result, the waveguides exhibit a refractive index distribution of “well+barrier” type. It is supposed that the change in local structure order of the substrate causes the “well” formation. The propagation loss is 2.0dB/cm for GLS and 2.2dB/cm for the GLSO glass waveguide.

High lithium ion conduction of sulfide glass-based solid electrolytes and their application to all-solid-state batteries

Sulfide glass-based solid electrolytes prepared by melt quenching and mechanical milling were reviewed. The sulfide and oxysulfide glass–ceramic electrolytes in the system Li 2S–P 2S 5–P 2O 5 with superionic Li 7P 3S 11 and Li 3.25P 0.95S 4 crystals exhibited high conductivity of over 10 −3 S cm −1 at room temperature and high electrochemical stability. Newly designed all-sulfide batteries 80SnS·20P 2S 5/80Li 2S·20P 2S 5/75Li 2S·25Cu were successfully fabricated; reversible charge–discharge capacities of more than 400 mAh g −1 were observed after the second to 10th cycles. The operation of those all-sulfide lithium secondary batteries is a first step for the realization of the all-solid-state monolithic batteries.

Processing and characterization of new passive and active oxysulfide glasses in the Ge–Ga–Sb–S–O system

New passive and active oxysulfide glasses have been prepared in the Ge–Ga–Sb–S–O system employing a two-step melting process which involves the processing of the chalcogenide glass (ChG) and its subsequent melting with amorphous GeO 2 or Sb 2O 3 powder. Optical characterization of the oxysulfide glasses has shown that the UV cut-off wavelength decreases with increasing oxygen content. Using Raman spectroscopy, correlations have been made between the formation of new Ge- and Sb-based oxysulfide structural units, the Sb content and the O/S ratio. We demonstrate the successful processing of active rare earth doped oxysulfide glasses by melting the chalcogenide glass with Er 2O 3 and Sb 2O 3 and also by melting the Er 3+ doped chalcogenide glass with Sb 2O 3. Modification of the emission spectra at 1500 nm of Er 3+ doped samples with the introduction of oxygen revealed that Er 3+ most likely exists in dual O- and S-neighbor environments. Finally, the photo-response of these new glasses upon near-IR femtosecond laser irradiation has been investigated as a function of Sb content and O/S ratio and shows that the glasses are photo-sensitive to NIR fs laser light with the magnitude of the photo-sensitivity dependent on the glass’ Sb content and O/S ratio.

Spectroscopy of titanium-doped gallium lanthanum sulfide glass

Titanium-doped gallium lanthanum sulfide (Ti:GLS) and gallium lanthanum oxysulfide (Ti:GLSO) glasses have an absorption band at ~500-600 nm that cannot be fully resolved because of its proximity to the band edge of the glass. At concentrations &gt;0.5% a shoulder at 980 nm is observed in Ti:GLS but not in Ti:GLSO. The emission spectra of Ti:GLS and Ti:GLSO both peak at 900 nm with lifetimes of 67 and 97 μs, respectively. We propose that the absorption at ~600 nm is due to the 2T2g→2Eg transition of octahedral Ti3+ and the 980 nm shoulder is due to Ti3+-Ti4+ pairs.

Processing and characterization of new oxysulfide glasses in the Ge–Ga–As–S–O system

New oxysulfide glasses have been prepared in the Ge–Ga–As system employing a two-step melting process which involves the processing of the chalcogenide glass (ChG) and its subsequent melting with amorphous GeO 2 powder. Optical characterization of the synthesized oxysulfide glasses has shown that the cut-off wavelength decreases with increasing oxygen content, and this has been correlated to results of Raman and infrared (IR) spectroscopies which show the formation of new oxysulfide structural units. X-ray photoelectron spectroscopy (XPS) analysis to probe the bonding environment of oxygen atoms in the oxysulfide glass network, has revealed the preferred formation of Ga–O and Ge–O bonds in comparison to As–O bonds. This work has demonstrated that melting a ChG glass with GeO 2 leads to the formation of new oxysulfide glassy materials.

Structure and properties of the 70Li2S · (30 − x)P2S5 · xP2O5 oxysulfide glasses and glass–ceramics

The 70Li2S·(30−x)P2S5·xP2O5 (mol%) oxysulfide glasses were prepared by the melt quenching method. The glasses were prepared in the composition range 0≦x ≦10. The glass–ceramics were prepared by heating the glasses over crystallization temperatures. The POnS3−n (n=1–3) oxysulfide units were produced in the glasses and glass–ceramics by partial substituting P2O5 for P2S5. In particular, the P2OS64− unit would be produced by substituting a small amount of P2O5 for P2S5. The oxygen atoms were incorporated into the Li7P3S11 crystal structure because the diffraction peaks of the oxysulfide glass–ceramic shifted to the higher angle side. The glass–ceramic with 3mol% of P2O5 exhibited the highest conductivity of 3.0×10−3Scm−1 and the lowest activation energy for conduction of 16kJmol−1. The P2OS64− dimer units in the oxygen-incorporated Li7P3S11 crystal would improve conductive behavior of the Li2S–P2S5 glass–ceramics.