Lithium Oxide Research Articles

Thermal Enhancement of Product Conductivity Raises Capacity in Solid-State Li-O2 Batteries

Li-O2 batteries are mainly limited by the poor conductivity of their discharge products as well as parasitic reactions with carbon-containing electrodes and electrolytes. Here, Li-O2 cells utilizing inorganic solid-state electrolytes are investigated as a means to operate at elevated temperature, thereby increasing the conductivity of discharge products. Growth of dense, conductive LixOy products further removes the need for high-surface area support structures commonly made of carbon. Patterned Au electrodes, evaporated onto Li7La3Zr2O12 (LLZO) solid electrolyte, are used to create a triple-phase boundary for the nucleation of the discharge product, with growth outward into the cell headspace with gaseous O2. Through capacity measurements and imaging, discharge product growths are estimated to reach a critical dimension of approximately 10 μm, far exceeding what would be possible for a conformal film based on its room temperature electronic conductivity. Raman spectroscopy and electrochemical mass spectrometry are used to characterize the discharge chemistry and reveal a mixed lithium oxide character, with evidence of trace lithium hydroxides and initial carbonate contamination. These results showcase that thermal enhancement of Li-O2 batteries could be a viable strategy to increase capacity when paired with solid electrolytes.

High-resolution Compton spectroscopy using x-ray microcalorimeters.

X-ray Compton spectroscopy is one of the few direct probes of the electron momentum distribution of bulk materials in ambient and operando environments. We report high-resolution inelastic x-ray scattering experiments with high momentum and energy transfer performed at a storage-ring-based high-energy x-ray light source facility using an x-ray transition-edge sensor (TES) microcalorimeter detector. The performance was compared with a silicon drift detector (SDD), an energy-resolving semiconductor detector, and Compton profiles were measured for lithium and cobalt oxide powders relevant to lithium-ion battery research. Spectroscopic analysis of the measured Compton profiles demonstrates the high-sensitivity to the low-Z elements and oxidation states. The line shape analysis of the measured Compton profiles in comparison with computed Hartree-Fock profiles is usually limited by the resolution of the semiconductor detector. We have characterized an x-ray TES microcalorimeter detector for high-resolution Compton scattering experiments using a bending magnet source at the Advanced Photon Source with a double crystal monochromator, providing monochromatic photon energies near 27.5keV. The momentum resolution below 0.16 atomic units (a.u.) was measured, yielding an improvement of more than a factor of 7 over a state-of-the-art SDD for the same scattering geometry. Furthermore, the lineshapes of narrow valence and broad core electron profiles of sealed lithium metal were clearly resolved using an x-ray TES compared to smeared and broadened lineshapes observed when using the SDD. High-resolution Compton scattering using the energy-resolving area detector shown here presents new opportunities for spatial imaging of electron momentum distributions for a wide class of materials with applications ranging from electrochemistry to condensed matter physics.

Physical characteristics of fluorine-doped lithium oxide as advanced material for solid-electrolyte-interphase applications of lithium–air batteries

Physical characteristics of fluorine-doped lithium oxide as advanced material for solid-electrolyte-interphase applications of lithium–air batteries

Performance Improvement of Lithium Metal Anode All-Solid-State Batteries By High-Speed Blowing of Abrasive Grains

All-solid-state lithium metal batteries (ASSLiMBs) are one of the candidates for a next-generation automotive battery. In particular, oxide-based SEs have relatively high electrochemical stability against lithium metal. Thus, ASSLiMB with oxide SE is expected to be long life and high energy density battery.Poor contact between the lithium metal and oxide SE is an issue to realize ASSLiMB with oxide SE. This poor contact causes high overvoltage at the SE-Li interface, and lithium dendrite grows into the SE, and it reaches to the cathode, then causing a short circuit at high-speed charging that exceeds critical current density (CCD). Several methods (e.g., thin-film insertion method, interface structure modification methods) are proposed to suppress the interface resistance and enhance the CCD; however, more low interface resistance and high CCD is required to achieve high-speed charging by ASSLiMB with oxide SE.In this study, we propose a thin surface structure control method by shot peening (S.P.) to suppress the interface resistance and increase the CCD of ASSLiMB with oxide SE. S.P. is a surface treatment method by blowing abrasive grains with high-pressure air. S.P. has the effect of imparting an uneven surface and compressive residual stresses to the surface. The uneven shape is expected to increase the interfacial stress and improve the contact property as the SE bites into the Li. The compressive residual stresses suppress crack initiation on the SE surface. It has been reported that Li dendrites grow with cracks, and suppression of cracks is expected to improve CCD . The S.P. has above two effects that can improve the lithium metal anode performance, so, we investigated the influence of the S.P. on the lithium metal anode performance. We also investigated the influence of the grain size on the electrode performance because the size of the surface roughness and the compressive residual stresses can be changed by the change of the grain size used in S.P.Pellets of oxide SE (Li6.25Ga0.25La3Zr2O12) synthesized by the solid phase reaction method were processed by S.P. with abrasive grain of Al2O3 powder. After the S.P., the surface of the pellet is coated with gold by gold sputtering. Three experiments with three abrasive gain sizes (50 µm,100 µm,300 µm) and the SE without S.P. were carried out to check the influence of the S.P.. Li metal was attached to both sides of the SE layer to construct a symmetric cell, and CCD measurements and electrochemical impedance spectroscopy measurements were performed. Surface characteristics were measured by surface three-dimensional scanning electron microscopy (surface 3DSEM) and indentation.Fig. 1 shows the CCD and interfaces resistance without S.P. and S.P. using each abrasive grain. As shown in the figure, higher CCD and low interface resistance are achieved for the samples with S.P. with 50 µm, and 100 µm grain size than non S.P. processed samples. On the other hand, the CCD of S.P. with 300 µm grain is almost the same as the non S.P. processed samples and the interface resistance is high. These results indicate that the S.P. can improve electrode performance, and there is an optimum S.P. grain size. From indentation, the fracture toughness of S.P. processed samples were higher than a sample without S.P., and the fracture toughness increased with increasing in grain diameter. This increase in fracture toughness may have suppressed the growth of Li dendrites into the SE, leading to an increase in CCD. The surface 3DSEM showed that the S.P. creates an uneven pattern on the SE pellet and the structure size is several µm. The structure size increases with the increase in the abrasive grain size. This unevenness improves the contact between SE and Li and suppresses the interface resistance. This interface resistance suppression depends on the structure size, and the lowest interface resistance is achieved for the S.P. with the smallest grain size of 50 µm. As a result of the balance between high compressive residual stress by small size grain and the low interface resistance by large size grain, the highest CCD is obtained by middle size grain of 100 µm.This study shows that S.P. can decrease the interfacial resistance of ASSLiMB and improve CCD. The unevenness caused by S.P. is on the order of several micrometers, and it can be said that S.P. can be applied to separators thinner than 100 micrometers. Figure 1

A Combined XPS and Computational Study of the Chemical Reduction of BMP‐TFSI by Lithium**

AbstractEmploying density functional theory (DFT) calculations and X‐ray photoelectron spectroscopy (XPS), we identify products of the reaction of the ionic liquid N,N‐butylmethylpyrrolidinum bis(trifluoromethylsulfonyl)imide (BMP‐TFSI) with lithium in order to model the initial chemical processes contributing to the formation of the solid electrolyte interphase in batteries. Besides lithium oxide, sulfide, carbide and fluoride, we find lithium cyanide or cyanamide as possible, thermodynamically stable product in the Li‐poor regime, whilst Li3N is the stable product in the Li‐rich regime. The thermodynamically controlled reaction products as well as larger fragments of TFSI persisting due to kinetic barriers could be identified by a comparison of experimentally and computationally determined core level binding energies.

Li7La3Zr2O12 Protonation as a Means to Generate Porous/Dense/Porous-Structured Electrolytes for All-Solid-State Lithium-Metal Batteries.

Ceramic Li7La3Zr2O12 (LLZO) represents a promising candidate electrolyte for next-generation all-solid-state lithium-metal batteries. However, lithium-metal batteries are prone to dendrite formation upon fast charging. Porous/dense and porous/dense/porous LLZO structures were proposed as a solution to avoid or at least delay the formation of lithium-metal dendrites by increasing the electrode/electrolyte contact area and thus lowering the local current density at the interface. In this work, we show the feasibility of producing porous/dense/porous LLZO by a new and scalable method. The method consists of LLZO chemical deep protonation in a protic or acidic solvent, followed by thermal deprotonation at high temperatures to create the porous structure by water and lithium oxide elimination. We demonstrate that the produced structure extends the lifetime of Li/LLZO/Li symmetric cells by a factor of 8 compared to a flat LLZO at a current density of 0.1 mA/cm2 and with a capacity of 1 mAh/cm2 per half-cycle. We also show clear improvement of the Li/LLZO/LiFePO4 full cell performance with a thermally deprotonated LLZO.

Oxidation and combustion of stabilized lithium metal powder (SLMP)

Power systems based on combustion are of interest for space missions where the use of solar and nuclear energy is impractical. A novel design of such systems involves the so-called filtration combustion of metal powders with oxygen supplied by a chemical oxygen generator. In missions to Mars and Venus, the atmospheric CO2 could be added to the oxygen flow. A stabilized lithium metal powder (SLMP) is a promising fuel for this application, but its oxidation and combustion in O2 and CO2 has not been studied yet. In the present work, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) have been used to investigate high-temperature oxidation of SLMP in O2/Ar and CO2 environments. Further, combustion of SLMP in vertical quartz tubes with two open ends at natural infiltration of O2 and CO2 has been studied in a laser ignition facility. The TGA has revealed the formation of lithium peroxide (Li2O2) in addition to lithium monoxide (Li2O) at temperatures below 400 °C. Scanning electron microscopy has shown that the oxidized particles are hollow shells, which implies that the oxidation process includes growth of a solid oxide layer on the surface of the lithium droplet and simultaneous growth of a cavity inside the droplet. The laser ignition of SLMP in O2 results in vigorous combustion of the top layer followed by the downward propagation of a counterflow combustion wave. The TGA and DSC have shown that the reaction of SLMP with CO2 is a multi-stage process, which includes the formation of lithium oxide and its subsequent conversion into lithium carbonate (Li2CO3). Self-sustained combustion of SLMP was not achieved in a CO2 environment, apparently because the formed products hinder the transport of CO2.

Smoothed particle hydrodynamics modeling and analysis of oxide reduction process for uranium oxides

A common kinetic feature for oxide reduction chemical/electrochemical processes is oxygen transport via a porous metallic layer, which has been considered as a rate-determining step for reducing uranium oxides to metallic uranium. Accounting this kinetic behavior must involve the resolution of the moving reactive interface between shrinking oxide and expanding metal phases. This study presents a numerical model using smoothed particles hydrodynamics (SPH) to effectively deal with the evolution of the shrinking core reaction interface and oxygen transport via mass transfer of lithium oxide (Li2O) species in multiple mass transfer domains. We successfully validated the proposed model against a theoretical derivation for the oxide reduction process handling a shrinking oxide core with molten salt and metal ash medium on a simple planar geometry. Armed with successful validation results, the model examined a realistic reactant geometry to extend the arguments beyond the one-dimensional analyses, allowing the proposed model to apply to general application scenarios with multi-dimensional geometry. This study demonstrated that the proposed model could simulate and evaluate an arbitrary reaction basket design without iterative experimental trials, which is prohibitive for a scaled high-temperature molten salt study in an inert environment. The construct potentially provides not only deep insights on multiphysics behaviors governing the process dynamics but also a robust framework for evaluating and screening candidate basket designs in the most cost-effective manner.

Structural, thermal and nuclear shielding properties of lithium lead phosphate glasses: Influence of lithium oxide additive

In this paper, the structural, thermal and nuclear radiation shielding properties of a new Lead–Lithium-Phosphate glass system with different amount lithium oxide were studied. The glass samples were prepared by the conventional melt-quenching method and they having compositions (75-x) P2O5– 25PbO- xLi2O with x = 0, 5, 10, 15, 20 mol%. The influence of Li2O content on the structural, thermal, radiation shielding properties, and other related properties of the synthesized glasses was studied. The structural properties were investigated using XRD and Raman spectroscopy. The glass transition temperature Tg and crystallization onset temperature Tx are estimated from the DSC profile.The GEANT4 Monte Carlo simulation code was used to estimate thermal neutron attenuation coefficient (μnt) in a wide neutron energy range of 0.0253–100 eV and ParShield code was used to calculate effective fast neutrons removal cross-section (∑R). The gamma-ray attenuation parameters such as mass attenuation coefficients (μm), effective atomic number (Zeff), effective electron density (Neff) and half-value layer (HVL) have been computed by using ParShield code in the energy range of 0.103–1.33 MeV. However, the total mass stopping power (MSP) and projected range (PR) values have been estimated for alpha particles (4He2+) and Triton particle (3H) by using SRIM in the energy range of 0.1–10 MeV.

Structural and optical characterization of semiconducting lithium modified zinc borate glassy system for UV band reject filter

The amalgamation of different compositions of 20ZnO.(80-x)B2O3.xLi2O (x = 10, 20, 30 and 40) glasses have been performed via well-known melt quenching technique. The absence of any sharp peak in X-ray Diffractograms confirms short range order i.e. amorphous nature of selected glass series. Calculations of density (ρ) have been done using the Archimedes principle and further different physical parameters such as molar volume (Vm), crystalline volume (Vc), bond density (nb), electronegativity difference (∆x), bond ionicity (Ib), boron-boron distance (<dB-B>), polaron radius (Rp), lithium ion concentration (N), lithium interionic separation (Ri), and lithium yield field strength (F) were calculated and found to be in correlation. Structural modifications occurring in the glass network with the addition of lithium oxide have been studied by identifying and careful assignment of structural groups present in the IR and Raman spectra on the basis of literature survey. The FTIR and Raman analysis revealed that the neutral triangular structural units (BØ3) transforms into charged tetrahedral borate units (BØ4−) which signifies the compactness of the glass network with enhancement in lithium concentration. The optical transmission studies revealed that glass composition 20ZnO.40B2O3.40Li2O acts as a UV band reject filter for wavelengths ranging from (247-323)nm whereas it acts as a transparent window with ∼80% transparency in the visible region. These optical features make glass composition 20ZnO.40B2O3.40Li2O suitable for radiation protection shields and may be used as an UV protective coating on window/sun glasses. The optical absorption spectrum has been in the light of the Mott and Davis model, Hydrogenic Excitonic model and modified Urbach energy model for extracting different optical parameters.

High-Temperature Passivation of the Surface of Candidate Materials for MSR by Adding Oxygen Ions to FLiNaK Salt.

The problem of tailoring the structural materials for MSR is solved by continuously overcoming the shortcomings of widely used materials and finding new ones. The materials commonly used in engineering may not be applicable for MSR due to their high corrosivity. Experiments were carried out to determine the corrosion rate of stainless steel 12Cr18Ni10Ti with different concentrations of oxide ions (by adding lithium oxide to the melt in the concentration range from 0 to 0.8 wt.%) in a FLiNaK melt. The formation of a protective oxygen-containing layer with a thickness of 1 micron has been realized. The corrosion rate decreases by an order of magnitude at the concentration of oxygen anions in the melt, in the range from 0.2 to 0.4% by weight, which may indicate high-temperature passivation of the material due to modification of the composition of the fluoride melt and reduction in its corrosion activity. In addition, the corrosion type of stainless steel in fluoride melts changes from the intercrystalline and pitting that is usually harmful to reactor material structure to total corrosion when lithium oxide is added. This is due to the “healing” of individual corrosion defects formed on the surface of the studied material by oxygen-containing compounds.

Elucidating the Step‐Wise Solid Electrolyte Interphase Formation in Lithium‐Ion Batteries with Operando Raman Spectroscopy

AbstractThe solid electrolyte interphase (SEI) is arguably one of the most critical components of the Li‐ion cell. Despite decades of studies of the SEI, its intrinsic complexity and the lack of suitable characterization tools still prevent a real consensus on the governing mechanisms to be reached. Herein, operando Raman spectroscopy supported by complimentary online electrochemical mass spectrometry is employed to study the SEI formation on Au in a model electrolyte based on LiClO4 in ethylene carbonate (EC). Both the electrolyte itself and cell contaminants, such as O2, CO2, and H2O, contribute in stepwise electro‐/chemical processes to the build‐up of the SEI. Effects associated with electrode/electrolyte double‐layer charging, electrode adsorbate polarization (stark effect), and SEI dissolution are discerned. Lithium carbonate and lithium oxide are identified as major products formed already ≈2 V versus Li+/Li. Although Raman spectroscopy provides deeper insights into the underlying mechanisms, complementary techniques are necessary to support spectral interpretations. Classical challenges in the field of surface science, such as contaminations, have to be systematically addressed if the puzzle of the SEI ever will be completed.

Understanding the Transport Phenomena in Solid State Battery (SSB)

The state-of-the-art Li-ion battery has energy density plateauing at ~300 Wh/kg. Replacing the graphite-based anode with Li metal is the easiest way to increase energy density. However, a lithium metal anode is prone to non-uniform plating/striping that leads to capacity decay and dendrite formation. Dendrites trigger short-circuiting and possible explosions as the liquid electrolytes that are used in Li-ion batteries are flammable. Solid-state batteries (SSBs) have the potential to enable Li-metal anodes as they are typically less reactive and nonflammable. Additionally, SSBs exhibit greater mechanical stability and can prevent dendritic growth [1,2]. Furthermore, solid electrolytes show much higher thermal stability, are non-toxic, and have high energy density, making the solid-state battery one of the best choices for the next generation of energy storage devices.Solid polymer electrolytes are an important class of materials for making solid-state batteries commercially viable. These have the potential to increase energy density and decrease contact resistance between anode and separator by formation of a suitable solid-electrolyte-interphase (SEI) [1]. However, this technology still has major hurdles to overcome, like lower Li-ion conductivity when compared to state-of-art ceramic separators. In recent years, garnet-type lithium oxide perovskites have gained attractiveness as state-of-art ceramic separators for SSBs. LLZTO is one such ceramic electrolyte that is being thoroughly investigated by researchers as it shows very high Li-ion conductivity at room temperature [2]. However, these materials suffer from poor interfacial contact. Recently, Yang, et al., [3] combined the best of both worlds with a new type of solid polymer separator which has better physical contact between separator and lithium and good li-ion conductivity at room temperature.In this work, we investigate the transport of Li-ions across both a solid polymer electrolyte and LLZTO solid electrolyte using a symmetric Li-cell configuration. Fig. 1 (a) and (c) show the Li plating/stripping cycling performance in a symmetric cell. The cell voltage measured during plating and stripping is to be very high for LLZTO compared to polymer electrolyte. A possible explanation may be due to high interfacial resistance arising between solid ceramic and lithium metal. Impedance spectroscopy was performed on both LLZTO and polymer separators after each current density step (24 h) and shown in Fig. 1 (b) and (d) respectively. The impedance increased with cycling for the LLZTO separator but decreased with cycling for polymer electrolyte. This may indicate that better interfacial contact between Li and polymer exists and that these connections may become more established while cycling. Furthermore, the transport of Li-ions across the separators will be analyzed using the transference number calculated using the Bruce-Vincent method. The influence of temperature and separator thickness on the transference number will also be used to characterize the nature of ion transport across such solid electrolyte separators. Such deep understanding of the transport mechanism is needed to minimize the different losses in SSBs and make it commercially viable.Figure 1: Li plating/stripping cycling performance of the (a) LLZTO electrolyte, and (c) PEO polymer electrolyte at different current density, with 12 minutes for each plating/stripping half cycle, for a total of 72 h at 70 ℃ temperature and their corresponding impedance are shown in (b) and (d) respectively. References R. Sahore, Z. Du, X. C. Chen, W. B. Hawley, A. S. Westover, and N. J. Dudney, Practical considerations for testing polymer electrolytes for high-energy solid-state batteries, ACS Energy Lett. 2021, 6, 2240-2247.A. Parejiya, R. Amin, M. B. Dixit, R. Essehli, C. J. Jafta, D. L. Wood, III, and I. Belharouak, Improving contact impedance via electrochemical pulses applied to lithium−solid electrolyte interface in solid-state batteries, ACS Energy Lett. 2021, 6, 3669−3675.Yang at al, Copper-coordinated cellulose ion conductors for solid-state batteries, Nature, 2021, 598, 590−596. Figure 1

Lithium oxide loss of lithium niobate nanocrystals during high-energy ball-milling

Congruent lithium niobate (LiNbO 3 ) prepared by sintering was ground under wet conditions in a planetary mill in order to produce nanocrystals. By using gradually lower sizes of the balls in the mill, the final particle size of the crystals could be reduced to about 12–15 nm. The particle size achieved as well as the lithium oxide (Li 2 O) loss of the lithium niobate particles were followed as a function of the grinding time. Lithium oxide was found to be released throughout the entire milling procedure, even in the case when the particle size no longer changed upon the grinding with a particular ball size. About 12% and 20% Li 2 O loss was detected upon grinding with 3 mm and 0.5 mm balls, respectively. X-ray diffractometry revealed the formation of a lithium-deficient phase, LiNb 3 O 8 , the presence of which was confirmed by means of Raman spectroscopy. The LiNb 3 O 8 :LiNbO 3 volume ratio achieved for 70 nm particle size as calculated from both the diffractograms and the lithium oxide loss determined by coulometric titration was assessed to be 0.39 (± 0.03). Correlation was revealed between the composition change of the nanopowder and the total surface area of the particle assembly calculated from dynamic light scattering measurements. • Lithium niobate nanopowders were produced with the help of a planetary mill. • The loss of lithium oxide and formation of LiNb 3 O 8 were observed upon milling. • The lithium loss during the wet grinding process was quantitatively characterized. • Particle size determined by SEM and DLS were in good agreement. • The surface area increase of the particle assembly correlated with the Li 2 O release.

Evaluating the Effect of Electrolyte Additive Functionalities on NMC622/Si Cell Performance

Unstable electrode/electrolyte interface is the major cause of degradation for silicon (Si)-based anodes for lithium (Li)-ion batteries. Development of functional electrolyte additives can provide a viable path toward stabilizing the dynamic Si/electrolyte interface, which will benefit the development of high energy density Li-ion batteries. Here, we evaluate polymerizable electrolyte additives with varying functional groups (fluorocarbon, thiophosphate, and fluorophosphazene). The additives are examined using LiNi0.6Mn0.2Co0.2O2/Si full cells where the cycle performance and impedance are measured. Electrochemical tests show that the fluorine-containing additives provide better passivation at the Si electrode, leading to enhanced full cell performance. Among the three additives examined, best electrochemical performance is observed from the fluorocarbon-containing compound, followed by fluorophosphazene- and thiophosphate-containing compounds. Characterization of the solid electrolyte interphase (SEI) on cycled electrodes using Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) reveal that higher concentration of fluorine and lithium oxide, and lower concentration of carbonate and organic species correlate with enhanced electrochemical performance.

Activating Lattice Oxygen in Layered Lithium Oxides through Cation Vacancies for Enhanced Urea Electrolysis.

Despite the fact that high-valent nickel-based oxides exhibit promising catalytic activity for the urea oxidation reaction (UOR), the fundamental questions concerning the origin of the high performance and the structure-activity correlations remain to be elucidated. Here, we unveil the underlying enhanced mechanism of UOR by employing a series of prepared cation-vacancy controllable LiNiO2 (LNO) model catalysts. Impressively, the optimized layered LNO-2 exhibits an extremely low overpotential at 10 mA cm-2 along with excellent stability after the 160 h test. Operando characterisations combined with the theoretical analysis reveal the activated lattice oxygen in layered LiNiO2 with moderate cation vacancies triggers charge disproportion of the Ni site to form Ni4+ species, facilitating deprotonation in a lattice oxygen involved catalytic process.

Activating Lattice Oxygen in Layered Lithium Oxides through Cation Vacancies for Enhanced Urea Electrolysis

AbstractDespite the fact that high‐valent nickel‐based oxides exhibit promising catalytic activity for the urea oxidation reaction (UOR), the fundamental questions concerning the origin of the high performance and the structure–activity correlations remain to be elucidated. Here, we unveil the underlying enhanced mechanism of UOR by employing a series of prepared cation‐vacancy controllable LiNiO2 (LNO) model catalysts. Impressively, the optimized layered LNO‐2 exhibits an extremely low overpotential at 10 mA cm−2 along with excellent stability after the 160 h test. Operando characterisations combined with the theoretical analysis reveal the activated lattice oxygen in layered LiNiO2 with moderate cation vacancies triggers charge disproportion of the Ni site to form Ni4+ species, facilitating deprotonation in a lattice oxygen involved catalytic process.

Dissecting the Solid Polymer Electrolyte-Electrode Interface in the Vicinity of Electrochemical Stability Limits.

Proper understanding of solid polymer electrolyte–electrode interfacial layer formation and its implications on cell performance is a vital step toward realizing practical solid-state lithium-ion batteries. At the same time, probing these solid–solid interfaces is extremely challenging as they are buried within the electrochemical system, thereby efficiently evading exposure to surface-sensitive spectroscopic methods. Still, the probing of interfacial degradation layers is essential to render an accurate picture of the behavior of these materials in the vicinity of their electrochemical stability limits and to complement the incomplete picture gained from electrochemical assessments. In this work, we address this issue in conjunction with presenting a thorough evaluation of the electrochemical stability window of the solid polymer electrolyte poly(ε-caprolactone):lithium bis(trifluoromethanesulfonyl)imide (PCL:LiTFSI). According to staircase voltammetry, the electrochemical stability window of the polyester-based electrolyte was found to span from 1.5 to 4 V vs Li+/Li. Subsequent decomposition of PCL:LiTFSI outside of the stability window led to a buildup of carbonaceous, lithium oxide and salt-derived species at the electrode–electrolyte interface, identified using postmortem spectroscopic analysis. These species formed highly resistive interphase layers, acting as major bottlenecks in the SPE system. Resistance and thickness values of these layers at different potentials were then estimated based on the impedance response between a lithium iron phosphate reference electrode and carbon-coated working electrodes. Importantly, it is only through the combination of electrochemistry and photoelectron spectroscopy that the full extent of the electrochemical performance at the limits of electrochemical stability can be reliably and accurately determined.

High-Strength Glass-Ceramic Material with Low Temperature Formation

Prospects for development of glass-ceramic materials on the lithium aluminosilicates base in order to increase the reliability of armor protection elements have been analyzed. Compositions of lithium aluminosilicate glasses with low content of lithium oxide have been developed, spodumene glass-ceramic materials were obtained on their base in conditions of low-temperature thermal treatment. Formation of structure of glass-ceramic materials based on model glasses after thermal treatment has been investigated and the influence of phase composition on mechanical properties has been established. It was determined that the developed glass-ceramic materials are feasible for the application against the action of high-energy munitions with significant penetrating ability, especially when used in combination with ceramic elements.

The Gd2-xMgxZr2O7-x/2 Solid Solution: Ionic Conductivity and Chemical Stability in the Melt of LiCl-Li2O.

Materials with pyrochlore structure A2B2O7 have attracted considerable attention owing to their various applications as catalysts, sensors, electrolytes, electrodes, and magnets due to the unique crystal structure and thermal stability. At the same time, the possibility of using such materials for electrochemical applications in salt melts has not been studied. This paper presents the new results of obtaining high-density Mg2+-doped ceramics based on Gd2Zr2O7 with pyrochlore structure and comprehensive investigation of the electrical properties and chemical stability in a lithium chloride melt with additives of various concentrations of lithium oxide, performed for the first time. The solid solution of Gd2−xMgxZr2O7−x/2 (0 ≤ x ≤ 0.10) with the pyrochlore structure was obtained by mechanically milling stoichiometric mixtures of the corresponding oxides, followed by annealing at 1500 °C. The lattice parameter changed non-linearly as a result of different mechanisms of Mg2+ incorporation into the Gd2Zr2O7 structure. At low dopant concentrations (x ≤ 0.03) some interstitial positions can be substituted by Mg2+, with further increasing Mg2+-content, the decrease in the lattice parameter occurred due to the substitution of host-ion sites with smaller dopant-ion. High-density ceramics 99% was prepared at T = 1500 °C. According to the results of the measurements of electrical conductivity as a function of oxygen partial pressure, all investigated samples were characterized by the dominant ionic type of conductivity over a wide range of pO2 (1 × 10–18 ≤ pO2 ≤ 0.21 atm) and T < 800 °C. The sample with the composition of x = 0.03 had the highest oxygen-ion conductivity (10−3 S·cm−1 at 600 °C). The investigation of chemical stability of ceramics in the melt of LiCl with 2.5 mas.% Li2O showed that the sample did not react with the melt during the exposed time of one week at the temperature of 650 °C. This result makes it possible to use these materials as oxygen activity sensors in halide melts.