Lanthanum Titanium Oxide Research Articles

Transient Phase-Mediated Li+ Transportation in the Lithium Lanthanum Titanate Solid-State Electrolyte.

The lithium lanthanum titanium oxide (LLTO) perovskite is one type of superior lithium (Li)-ion conductor that is of great interest as a solid-state electrolyte for all-solid-state lithium batteries. Structural defects and impurity phases formed during the synthesis of LLTO largely affect its Li-ion conductivity, yet the underlying Li+ diffusion mechanism at the atomic scale is still under scrutiny. Herein, we use aberration-corrected transmission electron microscopy to perform a thorough structural characterization of the LLTO ceramic pellet. We reveal a prevalent transient phase transition of (La, Ti)2O3 existing at the antiphase boundaries between single-crystalline LLTO domains. This transient phase exhibits a specific crystal orientation with the LLTO phase and shows a gradual structural transition to a tetragonal LLTO structure, which enables detailed crystallographic analysis to correlate their formation to the sintering process of LLTO powders into ceramic pellets. We also find that Li diffusion is retarded by this phase and correlated with the excess amount of La, which is corroborated by the theoretical evaluation of the atomistic mechanisms of Li diffusion across this phase.

Comment on "Bipolar Resistive Switching in Lanthanum Titanium Oxide and an Increased On/Off Ratio Using an Oxygen-Deficient ZnO Interlayer".

The Mott-based resistive switching random access memory (RRAM) has been considered as a promising candidate for next-generation nonvolatile mass storage. Its performance relies on the oxygen migration process. In ACS Appl. Mater. Interfaces 2022, 14, 17682-17690, Wang et al. demonstrated that inserting a ZnO layer between the top tungsten electrode and the lanthanum titanium oxide (LTO) layer can improve the ON/OFF current ratio of the RRAM. This improvement was attributed to the increased oxygen vacancies in the ZnO layer. We argue their interpretation with the role, significance, and statistics of the oxygen vacancy in the samples. Our experimental evidence contradicts their claim, and we propose that hydroxy groups should be the responsible candidate for their claimed oxygen vacancy peak at around 531-532 eV in the O 1s photoelectron spectroscopy observed in their samples. We thus propose an alternative mechanism for the ON/OFF ratio enhancement with the ZnO interlayer: the ZnO layer prevents the LTO oxygen and hydroxy groups migration and from reacting with the multivalent tungsten electrode.

Enhancing lithium-sulfur battery performance through electronic/ionic co-conductive multi-walled carbon nanotubes/lithium lanthanum titanium oxide separator modification

As one of the most promising energy storage devices, lithium-sulfur batteries (LSBs or Li-S batteries) are still facing obstacles due to the notorious shuttling of soluble polysulfide intermediates, accompanied by low S utilization, corrosion of the lithium anode, and rapid capacity fading, leading to a short cycling life. To overcome these issues and achieve high-performance LSBs, we introduce a modified separator composed of multi-walled carbon nanotubes/lithium lanthanum titanium oxide (MWCNTs/LLTO). The proposed MWCNTs/LLTO-modified separator improves the redox reaction kinetics from soluble higher-order lithium polysulfides to insoluble lower-order ones and ultimately to Li2S, thereby reducing the polysulfides dissolved in the electrolyte. It also serves as a physical barrier to adsorb polysulfides, efficiently preventing their diffusion from the cathode to the anode. LSBs adopting the MWCNTs/LLTO-modified separator exhibit higher ionic and electronic conductivity than their un-modified counterparts, leading to an initial specific capacity of 1496 mA/h/g (∼90% of the theoretical capacity) at 0.1 C, excellent rate capability performance, and a remarkable capacity retention of 80% after 200 cycles. Furthermore, the cells with S loading reaching up to 4.18 mg/cm2 further confirmed the beneficial impact of the MWCNTs/LLTO-modified separator.

(Invited) Cation and Anion Doping into Perovskite Lanthanum Titanium Oxides for Photocatalytic Water Splitting

Perovskite lanthanum titanium oxides have a great potential as photocatalysts for solar water splitting because of low cost, excellent operation stability and tunable surface chemistry. However, their solar energy conversion efficiency is low due to large band gap and the presence of surface trap states. This talk demonstrates our effort to dope nitrogen and metal ions into lanthanum titanium oxides to reduce the band gap and to suppress the surface trap states. Furthermore, the charge separation, migration and recombination processes have been studied.

Robust and Manufacturable Lithium Lanthanum Titanate-Based Solid-State Electrolyte Thin Films Deposited in Open Air.

State-of-the-art solid-state electrolytes (SSEs) are limited in their energy density and processability based on thick, brittle pellets, which are generally hot pressed in vacuum over the course of several hours. We report on a high-throughput, open-air process for printable thin-film ceramic SSEs in a remarkable one-minute time frame using a lithium lanthanum titanium oxide (LLTO)-based SSE that we refer to as robust LLTO (R-LLTO). Powder XRD analysis revealed that the main phase of R-LLTO is polycrystalline LLTO, accompanied by selectively retained crystalline precursor phases. R-LLTO is highly dense and closely matched to the stoichiometry of LLTO with some heterogeneity throughout the film. A minimal presence of lithium carbonate is identified despite processing fully in ambient conditions. The LLTO films exhibit remarkable mechanical properties, demonstrating both flexibility with a low modulus of ∼35 GPa and a high fracture toughness of >2.0 . We attribute this mechanical robustness to several factors, including grain boundary strengthening, the presence of precursor crystalline phases, and a decrease in crystallinity or ordering caused by ultrafast processing. The creation of R-LLTO-a ceramic material with elastic properties that are closer to polymers with higher fracture toughness-enables new possibilities for the design of robust solid-state batteries.

Porous lanthanum titanium oxide nanostructure composite membrane to enhance the power output and chemical durability of low-humidifying polymer electrolyte fuel cells: impact of additive morphology

Tuning the morphologies for improving the properties of the additive materials receives immense attention during the fabrication of proton-exchange membranes for fuel cells. This study reports the synthesis of lanthanum titanium oxide (LTO) nanostructures with different morphologies (cube, spherical, and tubular) via the pyrolysis of nanofibers containing metal precursors. A mixed matrix membrane is fabricated by incorporating LTO cubes (LTO-C), LTO spheres (LTO-S), or LTO tubes (LTO-T) into a Nafion matrix, with improved physicochemical, thermomechanical, and electrochemical properties compared to those of the unmodified Nafion and Nafion-212 membranes. We investigate the effect of LTO morphology on the performance of the Nafion membranes in low-humidity polymer electrolyte fuel cells (LH-PEFCs). The water retention and diffusion behavior of LTO-T nanostructures improve the proton conductivity and LH-PEFC performance of the Nafion composite membranes. The coexistence of La3+ and Ti4+ affords efficient radical scavenging during long-term LH-PEFC operation, which realizes higher durability for the composite membranes compared to Nafion. Accordingly, this study proposes a novel strategy to resolve the major challenges associated with the operation of LH-PEFCs with Nafion membranes: dehumidification and oxidative degradation.

Investigate the Function and Structure of (Fe,Cr) La2Ti2O7 Photocatalyst Calcined under the Nitrogen Atmosphere

Extensive research has been conducted on enhancing the photocatalytic activity of Lanthanum titanium oxide (La2Ti2O7) based photocatalysts. However, these photocatalysts were found to be inactive under visible light. To address this limitation, a modification was developed by co-doping Fe and Cr on La2Ti2O7 to enable visible light driven photocatalytic response. The calcination of (Fe,Cr) La2Ti2O7 was carried out under nitrogen atmosphere at various temperatures for 24 h. The results showed that the (Fe,Cr)-La2Ti2O7 calcined at 1250 °C for 24 h exhibited the highest methylene blue degradation under visible light. Synchrotron X-ray absorption spectroscopy indicated that Fe and Cr were substitutionally located adjacent to the Ti atom within the La2Ti2O7 structure. This metal substitutionally facilitated electron transfer and perturbed the p-d hybridization by modifying the local electronic structure of the surrounding oxygen atoms and transition metal ions, thereby reducing the band gap energy and enhancing the photocatalytic capability. Copyright © 2023 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

First principles study on Li metallic phase nucleation at grain boundaries in a lithium lanthanum titanium oxide (LLTO) solid electrolyte

Among various intergranular microstructures, pore spaces in SEs play a critical role in Li-metal nucleation in SEs. To realize Li-metal nuclei-free inside the SE, removing pore spaces is essential and a commonly applicable design strategy to all SEs.

Lithium incorporation enhanced resistive switching behaviors in lithium lanthanum titanium oxide-based heterostructure

• Self-rectifying resistive switching device based on lithium lanthanum titanium oxide. • The simplified device has a high rectification ratio and on/off ratio. • Schottky barrier assisted model explains the electronic bipolar resistive switching. • Li + migration accelerates electron injection and enhances the performance of the device. Resistive switching devices with a high self-rectifying ratio are important for achieving the crossbar memristor array that overcomes the sneak current issue. Herein, we demonstrate a single amorphous lithium lanthanum titanium oxide (LLTO) layer based Pt/LLTO/Pt device possessing a self-rectifying ratio higher than 1 × 10 4 that is comparable to the reported devices with complicated multi-layer stacking structures. Moreover, the device shows forming-free and highly uniform bipolar resistive switching (BRS) characteristic that facilitates the potential applications. The trap-controlled and trap-free space charge limited conductions are demonstrated to dominate the high and low resistance states of the device, respectively. The fast migration of lithium ions under external voltage accelerates the electron injection across the Pt/LLTO interface and also the space charge accumulation in the LLTO layer, and as a result, the high performance of the Pt/LLTO/Pt device was achieved. As demonstrated Pt/LLTO/Pt device sheds a light on the potential applications of the lithium ionic conductors in self-rectifying resistive switching devices.

Atomic Defect Mediated Li-Ion Diffusion in a Lithium Lanthanum Titanate Solid-State Electrolyte.

Lithium lanthanum titanium oxide (LLTO) as a fast Li-ion conductor is a promising candidate for future all-solid-state Li batteries. Fundamental understanding of the microstructure of LLTO and its effect on the Li+ diffusion mechanism, especially across different length scales and interfaces, is a prerequisite to improving the material design and processing development of oxide-based solid electrolytes. Herein, through detailed structural analysis of LLTO ceramic pellets by aberration-corrected transmission electron microscopy, we discovered previously unreported intrinsic planar defects in LLTO single-crystal grains. These planar defects feature an antiphase boundary along specific crystal planes with a "rock-salt" structure enriched by Li within a few atomic layers. Corroborated by density-functional-theory-based calculations, we show an increased diffusion barrier across these planar defects inevitably lowers the bulk Li+ diffusivity of the oxide electrolyte.

Bipolar Resistive Switching in Lanthanum Titanium Oxide and an Increased On/Off Ratio Using an Oxygen-Deficient ZnO Interlayer.

The present study pioneered an oxygen migration-driven metal to insulator transition Mott memory, a new type of nonvolatile memory using lanthanum titanium oxide (LTO). We first show the reset first bipolar property without an initial electroforming process in LTO. We used oxygen-deficient ZnO as an interlayer between LTO and a W electrode to clarify whether oxygen migration activates LTO as the Mott transition. ZnO oxygen deficiency provides oxygen ion migration paths as well as a reservoir, facilitating oxygen migration from LTO to the W electrode. Thus, including the ZnO interlayer improved oxygen migration between LTO and the W electrode, achieving a 10-fold increased on/off current ratio. The current research contributes to a better understanding of valence change Mott memory by exploring the LTO resistive switching mechanism and ZnO interlayer influences on the oxygen migration process.

Electric field induced Mott transition and bipolar resistive switching in La2Ti2O7-x thin film

The oxygen ion migration-induced resistive switching is a complex process with multiple mechanisms. This study investigated resistive switching properties and mechanism for strongly correlated materials lanthanum titanium oxide La2Ti2O7-x (LTO) using spectromicroscopy and density functional theory simulation. Bipolar resistive switching without an electroforming process was first reported in LTO film. The mechanism can be explained by oxygen ion migration induced band-filling controlled Mott transition in LTO. Oxygen ion migration-induced reduction and oxidation of LTO can increase and decrease Ti 3d orbital filling state, which in turn increases and reduces Mott-Hubbard gap and LTO resistance, respectively. In addition, the RRAM device, TiN/LTO/Pt, shows stable endurance, retention, and small variability at room temperature and 85 ℃, with a stable on/off-state current density, which is independent of the electrode size. This work not only demonstrates that LTO and other strongly correlated materials are potential candidates to prepare resistive random access memory based on oxygen ion migration induced Mott-transition mechanism but also indicates that intrinsic resistance change in switching layers between top and bottom electrodes also contribute to overall resistive switching.

Structural origin of low Li-ion conductivity in perovskite solid-state electrolyte

Perovskite solid-state electrolyte, Lithium Lanthanum Titanium Oxide, has long been considered as a promising candidate enabling all-solid-state Li batteries due to its high bulk Li-ion conductivity and wide electrochemical window. However, the Li-ion conductivity at so called “grain boundaries” (GBs) off LLTO pellets is much lower than that of its bulk phase. Thus, understanding the structural origin of the low Li-ion conductivity of LLTO is critical yet remains largely elusive. Here, we identify two types of GBs at different length scales, namely “macro” and “micro” GBs in LLTO pellets and originate them to the processing of LLTO. We also find a nanosized Li-poor orthogonal phase at micro-GBs, which largely deteriorate the Li conduction. Corroborated by electrochemical measurements, we revealed the phase transformation from tetragonal Li0.33La0.56TiO3 to orthogonal Li0.18La0.6TiO3 during the heat-treatment process is responsible for this deterioration. During phase transformation process, La atoms move to the original Li-rich layer and block the diffusion path of Li-ions in LLTO. These results reveal the structural origin of low Li-ion conductivity in LLTO pellets and provide insights to prevent Li-loss induced phase transformation for commercial application of LLTO.

Effect of single atom Platinum (Pt) doping and facet dependent on the electronic structure and light absorption of Lanthanum Titanium Oxide (La2Ti2O7): A Density Functional Theory study

Charge generation and separation are two key processes for semiconductor photocatalysis. Here, we use Pt as a single atom catalyst to systematically examine the facet-dependent electronic band structure and light absorption of the layered perovskite-type wide-gap semiconductor, lanthanum titanium oxide (La2Ti2O7, LTO) by means of density functional theory simulations. It is found that single Pt atom doping of different LTO surfaces (here, (100), (101) and (001)) can not only create states in the bandgap that would promote the formation of recombination centers, but also shift the optical absorption edge to the visible region. Interestingly, the Pt doping forms a heterojunction, with the valence band maximum consisting of Pt states and the conduction band minimum consisting of LTO states, respectively. To study the facet dependent surface activity, acetic acid (CH3COOH) was used as a model molecule to investigate the adsorption and charge transfer on the (101), (100) and (001) Pt-LTO surface facets. The results show that the (101) facet could enable stronger adsorption of CH3COOH by promoting more electron transfer during the interfacial interaction. Our theoretical findings aim to promote the design and optimization of the single atom catalysts (SACs) for photocatalytic applications and other broad catalysis systems.

Role of Pairwise Reactions on the Synthesis of Li0.3La0.57TiO3 and the Resulting Structure-Property Correlations.

The performance of single-ion conductors is highly sensitive to the material's defect chemistry. Tuning these defects is limited for solid-state reactions as they occur at particle-particle interfaces, which provide a complex evolving energy landscape for atomic rearrangement and product formation. In this report, we investigate the (1) order of addition and (2) lithium precursor decomposition temperature and their effect on the synthesis and grain boundary conductivity of the perovskite lithium lanthanum titanium oxide (LLTO). We use an intimately mixed sol-gel, a solid-state reaction of Li precursor + La2O3 + TiO2, and Li precursor + amorphous La0.57TiOx as different chemical routes to change the way in which the elements are brought together. The results show that the perovskite can accommodate a wide range of Li deficiencies (upward of 50%) while maintaining the tetragonal LLTO structure, indicating that X-ray diffraction (XRD) is insufficient to fully characterize the chemical nature of the product (i.e., Li-deficient LLTO may behave differently than stoichiometric LLTO). Variations in the relative intensities of different reflections in XRD suggest variations in the La ordering within the crystal structure between synthesis methods. Furthermore, the choice of the precursor and the order of addition of the reactants lower the time required to form a pure phase. Density functional theory calculations of the formation energy of possible reaction intermediates support the hypothesis that a greater thermodynamic driving force to form LLTO leads to a greater LLTO yield. The retention of lithium is correlated with the thermal decomposition temperature of the Li precursor and the starting material mixing strategy. Taking the results together suggests that cations that share a site with Li should be mixed early to avoid ordering. Such cation ordering inhibits Li motion, leading to higher Li ion resistance.

Advances in solid lithium ion electrolyte based on the composites of polymer and LLTO/LLZO of rare earth oxides

AbstractComposite solid electrolyte is a promising solution for the development of new generation of safe and high‐performance all‐solid‐state lithium batteries (ASSLBs). It combines both the advantages of inorganic electrolyte and organic polymer electrolyte, having high ionic conductivity, mechanical strength, good contact with the electrodes and high processability. In the recent decades, rare earth oxides have attracted wide attentions from researchers because of their high ionic conductivity. China is abundant in rare earth resources, so has a good chance to provide the world with high quality rare earth containing functional materials. This review paper focuses on the recent progress in the studies of composite solid electrolyte of polymer and rare earth containing lithium lanthanum zirconium and lithium lanthanum titanium oxides, and gains insights into the challenges in the field, and hopefully helps in the rational design of high performance electrolyte for the development of ASSLBs.

All-solid-state reference electrode based on a solid-state electrolyte of high densified Lithium lanthanum titanium oxide (LLTO)

All-solid-state reference electrode based on a solid-state electrolyte of high densified Lithium lanthanum titanium oxide (LLTO)

From Slater to Mott physics by epitaxially engineering electronic correlations in oxide interfaces

Using spin-assisted ab initio random structure searches, we explore an exhaustive quantum phase diagram of archetypal interfaced Mott insulators, i.e. lanthanum-iron and lanthanum-titanium oxides. In particular, we report that the charge transfer induced by the interfacial electronic reconstruction stabilises a high-spin ferrous Fe2+ state. We provide a pathway to control the strength of correlation in this electronic state by tuning the epitaxial strain, yielding a manifold of quantum electronic phases, i.e. Mott-Hubbard, charge transfer and Slater insulating states. Furthermore, we report that the electronic correlations are closely related to the structural oxygen octahedral rotations, whose control is able to stabilise the low-spin state of Fe2+ at low pressure previously observed only under the extreme high pressure conditions in the Earth’s lower mantle. Thus, we provide avenues for magnetic switching via THz radiations which have crucial implications for next generation of spintronics technologies.

Reduction of Grain Boundary Resistance of La0.5Li0.5TiO3 by the Addition of Organic Polymers.

The organic solvents that are widely used as electrolytes in lithium ion batteries present safety challenges due to their volatile and flammable nature. The replacement of liquid organic electrolytes by non-volatile and intrinsically safe ceramic solid electrolytes is an effective approach to address the safety issue. However, the high total resistance (bulk and grain boundary) of such compounds, especially at low temperatures, makes those solid electrolyte systems unpractical for many applications where high power and low temperature performance are required. The addition of small quantities of a polymer is an efficient and low cost approach to reduce the grain boundary resistance of inorganic solid electrolytes. Therefore, in this work, we study the ionic conductivity of different composites based on non-sintered lithium lanthanum titanium oxide (La0.5Li0.5TiO3) as inorganic ceramic material and organic polymers with different characteristics, added in low percentage (<15 wt.%). The proposed cheap composite solid electrolytes double the ionic conductivity of the less cost-effective sintered La0.5Li0.5TiO3.

The Characterizations of La&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;Ti&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O&amp;lt;sub&amp;gt;7&amp;lt;/sub&amp;gt; Thin Films Deposited by Pulsed Laser Deposition at Different Annealing Temperatures

Lanthanum titanium oxide thin films are sometimes used in high-temperature environments. Therefore, it is worth paying attention to the thermal stability of the La₂Ti₂O₇ films. La₂Ti₂O₇ target was made through traditional solid-state reaction way to study the effect of substrate temperature on the characteristics of LTO thin films; A Set of lanthanum titanium oxide thin films has been deposited on to Si (100) substrate through Pulsed laser deposition at different annealing temperatures. The results of X-ray diffraction indicated that the prepared LTO thin films at temperatures up to 700°C are amorphous, while the profilometer Dektak-XT conducted to determine the thickness and roughness of La₂Ti₂O₇ films. The obtained result pointed that the thin film thickness decreased by increasing annealing temperature linearly, and the roughness was inversely proportioning to the increasing of substrate temperature. The value of the lowest roughness equal to 12.28 nm for the thinner film with a thickness of 253.46 nm, while the highest roughness was found to be 14.74 nm for the thicker film at 323.05 nm, which were deposited at 700°C and 500°C respectively, therefore it has been remarked that the annealing temperature influenced the morphology, thickness, and roughness of the LTO thin film.