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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Nanoscale Control of Polar Surface Phases in Layered van der Waals CuInP 2 S 6

Antiferroelectric (AFE) materials, in which alternating dipole moments cancel out to a zero net macroscopic polarization, can be used for high-density energy storage and memory applications. The AFE phase can exist in bulk CuInP 2 Se 6 , CuBiP 2 S 6 , and a few other transition-metal thiophosphates below 200 K. The required low temperature poses challenges for practical applications. In this work, we report the coexistence of ferrielectric (FE) states and a stable surface phase that does not show piezoelectric response (“zero-response phase”) in bulk CuInP 2 S 6 at room temperature. Using piezoresponse force microscopy (PFM) tomographic imaging together with density functional theory, we find that direct and alternating voltages can locally and stably convert FE to zero-response phases and vice versa. While PFM loops show pinched hystereses reminiscent of antiferroelectricity, PFM tomography reveals that the zero-response areas form only on top of the FE phase in which the polarization vector is pointing up. Theoretical calculations suggest that the zero-response phase may correspond to AFE ordering where stacked CuInP 2 S 6 layers have alternating polarization orientations thereby leading to a net-zero polarization. Consistent with experimental findings, theory predicts that the FE polarization pointing down is robust up to the top surface, whereas FE polarization pointing up energetically favors the formation of an AFE surface layer, whose thickness is likely to be sensitive to local strains. AFE order is likely to be more robust against detrimental size effects than polar order, therefore providing additional opportunities to create multifunctional heterostructures with 2D electronic materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Cation-Driven Assembly of Bilayered Vanadium Oxide and Graphene Oxide Nanoflakes to Form Two-Dimensional Heterostructure Electrodes for Li-Ion Batteries

Lithium preintercalated bilayered vanadium oxide (LVO or δ-Li x V 2 O 5 ·nH 2 O) and graphene oxide (GO) nanoflakes were assembled using a concentrated lithium chloride solution and annealed under vacuum at 200 °C to form two-dimensional (2D) δ-Li x V 2 O 5 ·nH 2 O and reduced GO (rGO) heterostructures. Here we found that the Li + ions from LiCl enhanced the oxide/carbon heterointerface formation and served as stabilizing ions to improve structural and electrochemical stability. The graphitic content of the heterostructure could be easily controlled by changing the initial GO concentration prior to assembly. We found that increasing the GO content in our heterostructure composition helped inhibit the electrochemical degradation of LVO during cycling and improved the rate capability of the heterostructure. A combination of scanning electron microscopy and X-ray diffraction was used to help confirm that a 2D heterointerface formed between LVO and GO, and the final phase composition was determined using energy-dispersive X-ray spectroscopy and thermogravimetric analysis. Scanning transmission electron microscopy and electron energy-loss spectroscopy were additionally used to examine the heterostructures at high resolution, mapping the orientations of rGO and LVO layers and locally imaging their interlayer spacings. Further, electrochemical cycling of the cation-assembled LVO/rGO heterostructures in Li-ion cells with a non-aqueous electrolyte revealed that increasing the rGO content led to improved cycling stability and rate performance, despite slightly decreased charge storage capacity. The heterostructures with 0, 10, 20, and 35 wt % rGO exhibited capacities of 237, 216, 174, and 150 mAh g –1 , respectively. Moreover, the LVO/rGO-35 wt % and LVO/rGO-20 wt % heterostructures retained 75% (110 mAh g–1) and 67% (120 mAh g –1 ) of their initial capacities after increasing the specific current from 20 to 200 mA g –1 , while the LVO/rGO-10 wt % sample retained only 48% (107 mAh g –1 ) of its initial capacity under the same cycling conditions. In addition, the cation-assembled LVO/rGO electrodes exhibited enhanced electrochemical stability compared to electrodes prepared through physical mixing of LVO and GO nanoflakes in the same ratios as the heterostructure electrodes, further revealing the stabilizing effect of a 2D heterointerface. The cation-driven assembly approach, explored in this work using Li + cations, was found to induce and stabilize the formation of stacked 2D layers of rGO and exfoliated LVO. The reported assembly methodology can be applied for a variety of systems utilizing 2D materials with complementary properties for applications as electrodes in energy storage devices.

25 ENERGY STORAGE↗
DOE OSTI2022

Electronic states dressed by an out-of-plane supermodulation in the quasi-two-dimensional kagome superconductor CsV 3 Sb 5

CsV 3 Sb 5 has attracted much recent attention as the first quasi-two-dimensional (2D) kagome superconductor. While the kagome layers are 2D in nature, increasing evidence has pointed to the importance of out-of-plane correlation in this material. However, it remains unclear whether such correlation can change the fundamental electronic structure of the quasi-2D system. Here, we reveal this missing piece of information, using angle-resolved photoemission spectroscopy, complemented by scanning tunneling microscope measurements. The three-dimensional electronic structures in the high-temperature state are revealed, which agree well with density-functional theory calculations. Electron energy bands are observed in the low-temperature state that exhibit additional periodicities along the out-of-plane momentum. Furthermore, these results reveal a direct response to the out-of-plane electronic supermodulation in the single-particle spectral function of CsV 3 Sb 5 , thus establishing an electronic platform to examine emergent phenomena beyond 2D limit in kagome superconductors.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Medium-Entropy Engineering of Magnetism in Layered Antiferromagnet Cu x Ni 2(1- x ) Cr x P 2 S 6

Antiferromagnetic van der Waals-type M 2 P 2 X 6 compounds provide a versatile material platform for studying 2D magnetism and relevant phenomena. Establishing ferromagnetism in 2D materials is technologically valuable. Though magnetism is generally tunable via a chemical way, it is challenging to induce ferromagnetism with isovalent chalcogen and bimetallic substitutions in M 2 P 2 X 6 . Here, we report co-substitution of Cu 1+ and Cr 3+ for Ni 2+ in Ni 2 P 2 S 6 , creating Cu x Ni 2(1-x) Cr x P 2 S 6 medium-entropy alloys spanning a full substitution range (x = 0 to 1). Such substitution strategy leads to a unique evolution in crystal structure and magnetic phases that are distinct from traditional isovalent bimetallic doping, with Cu and Cr co-substitution enhancing ferromagnetic correlations and generating a weak ferromagnetic phase in intermediate compositions. This aliovalent substitution strategy offers a universal approach for tuning layered magnetism in antiferromagnetic systems, which along with the potential for light-matter interaction and high-temperature ferroelectricity, can enable multifunctional device applications.

2D magnetism↗
DOE OSTI2026

Planar Systems for Quantum Information

This project aims to develop two‐dimensional (2D) moiré materials as a quantum simulator to implement model Hamiltonians and their phase diagrams. Progress in quantum information science (QIS) requires the development of advanced quantum materials systems. The rich family of layered van der Waals materials and their heterostructures present opportunities to create previously unrealized types of applications for QIS. Specifically, when two layers of van der Waals materials are overlaid with a small twist angle or/and lattice mismatch, a moiré superlattice with a period of about ten nanometers is formed. This provides a periodic trapping potential for electrons. Electrons can tunnel between the traps and repel each other by their mutual Coulomb interactions. The platform of 2D moiré materials provides many attractive features, including tunability of length and energy scales, charge density, and even lattice symmetry. It presents new possibilities for realizing quantum simulation of the many-body physics in a solid-state platform. This integrated team of six investigators seeks to develop relevant theoretical treatments to link ab-initio studies of 2D moiré materials to model Hamiltonians and to evaluate correlated phases predicted by these model Hamiltonians in the relevant regimes. On the experimental side, the team aims to develop methods to realize a homogeneous and highly controlled potential landscape for the electrons and to initiate, protect, and measure their quantum many-body states.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Remote epitaxy and selective epitaxy on vdW materials for layer transfer

Remote epitaxy is recently gaining huge attention forthe growth of single-crystal thin films and their isolation from the substrate for heterogeneous integration.Despite the recent progress, there are challenges inengineering the interface and optimizing the materialquality. Here, we introduce two approaches that could overcome the issues. As the first approach, we show directly grown 2D materials as a template for remote epitaxy of III-V and III-N materials. This ensuresa pristine interface without transfer process-related contaminations and damages. Second, we show theuse of nanopatterned graphene for selective epitaxyand lateral overgrowth of single-crystal films. This allows for the use of materials as substrates and epilayers which is not possible in remote epitaxy.

Kim, Hyunseok↗
DOE OSTI2023

Role of Cations in the Cation-Driven Assembly Process and their Effect on the Charge Storage Properties of Bilayered Vanadium Oxide and Reduced Graphene Oxide Heterostructures in Alkali Ion Systems

Exfoliated δ-Li x V 2 O 5 ·nH 2 O (ex-LVO) and reduced graphene oxide (rGO) heterostructures were constructed using different assembling cations (i.e., Li⁺, Na⁺, and K⁺ ions). The ex-LVO and rGO nanoflakes were stacked together using a concentrated chloride solution of each assembling cation and vacuum annealed at 200 °C to form three distinct two-dimensional (2D) layered architectures. X-ray diffraction and thermogravimetric analysis confirmed that the assembling ions can control the interlayer spacing of the bilayered vanadium oxide (BVO) phase as well as impact the crystallographic water content, which in turn affects the electrochemical performance. Scanning electron microscopy, scanning transmission electron microscopy (STEM), electron energy-loss spectroscopy (EELS), and X-ray photoelectron spectroscopy confirmed that a 2D heterointerface formed between LVO and rGO and that the cations used to assemble the heterostructure are trapped in the interlayer BVO region. High-resolution STEM imaging also showed the rGO dispersion throughout the LVO layers. Moreover, STEM-EELS identified a V 2 O 3 phase that forms along the rGO interface and can stabilize the materials during cycling. A charge storage mechanism analysis, combined with the galvanostatic intermittent titration technique, found that increased interlayer spacings of the BVO phase and using the assembling cations to define intercalation sites for identical charge-carrying ions lead to improved ion diffusion and increased capacities during cycling. Therefore, the Li⁺ and Na⁺ ion assembled heterostructures showed improved charge-carrying ion diffusion and charge storage capacities in each of their respective charge storage systems (i.e., Li-ion and Na-ion half-cells). In total, the cation used for heterostructure assembly can modify the final material structure and tailor the ion diffusion and charge storage capacity to tune its properties for the desired electrochemical system using a variety of 2D materials.

25 ENERGY STORAGE↗
DOE OSTI2023

Wafer-Scale Synthesis of 2D Materials by an Amorphous Phase-Mediated Crystallization Approach

The interest in the wafer-scale growth of two-dimensional (2D) materials, including transition metal dichalcogenides (TMDCs), has been rising for transitioning from lab-scale devices to commercial-scale systems. Among various synthesis techniques, physical vapor deposition, such as pulsed laser deposition (PLD), has shown promise for the wafer-scale growth of 2D materials. However, due to the high volatility of chalcogen atoms (e.g., S and Se), films deposited by PLD usually suffer from a lack of stoichiometry and chalcogen deficiency. To mitigate this issue, excess chalcogen is necessary during the deposition, which results in problems like uniformity or not being repeatable. This study demonstrates a condensed-phase or amorphous phase-mediated crystallization (APMC) approach for the wafer-scale synthesis of 2D materials. This method uses a room-temperature PLD process for the deposition and formation of amorphous precursors with controlled thicknesses, followed by a post-deposition crystallization process to convert the amorphous materials to crystalline structures. This approach maintains the stoichiometry of the deposited materials throughout the deposition and crystallization process and enables the large-scale synthesis of crystalline 2D materials (e.g., MoS 2 and WSe 2 ) on Si/SiO 2 substrates, which is critical for future wafer-scale electronics. We show that the thickness of the layers can be digitally controlled by the number of laser pulses during the PLD phase. Optical spectroscopy is used to monitor the crystallization dynamics of amorphous layers as a function of annealing temperature. The crystalline quality, domain sizes, and the number of layers were explored using nanoscale and atomistic characterization (e.g., AFM, STEM, and EDS) along with electrical characterization to explore process–structure–performance relationships. Finally, this growth technique is a promising method that could potentially be adopted in conventional semiconductor industries for wafer-scale manufacturing of next-generation electronic and optoelectronic devices.

2D electronics↗
DOE OSTI2020

Strong polaronic effect in a superatomic two-dimensional semiconductor

Crystalline solids assembled from superatomic building blocks are attractive functional materials due to their hierarchical structure, multifunctionality, and tunability. An interesting example is Re 6 Se 8 Cl 2 , in which the Re 6 Se 8 building blocks are covalently linked into two-dimensional (2D) sheets that are stacked into a layered van der Waals solid. It is an indirect gap semiconductor that, when heavily doped, becomes a superconductor at low temperatures. Given the finite electronic bandwidths (300–400 meV), carrier properties in this material are expected to be strongly influenced by coupling to phonons. Here, we apply angle-resolved photoemission spectroscopy to probe the valence band edge (VBE) of Re 6 Se 8 Cl 2 . We find that dispersion of the VBE is a strong function of temperature. The bandwidth is W = 120 ± 30 meV at 70 K and decreases by one order of magnitude to W ~ 10 ± 20 meV as temperature is increased to 300 K. This observation reveals the dominant polaronic effects in Re 6 Se 8 Cl 2 , consistent with the Holstein polaron model commonly used to describe molecular solids.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Functionalization of Monolayer MoS 2 with Layered Multimolecular Architectures

Two dimensional van der Waals materials have attracted attention due to their unique properties that arise in the monolayer versus bulk limits. Monolayer MoS 2 has been at the forefront of 2D materials due to its broad applicability in catalysis, photovoltaics, and spintronics. To realize the capabilities of MoS 2 enabled technology, it is necessary to engineer interfaces where charge carriers can be funneled toward or away from the surface. Molecular systems are a versatile strategy to enable this. Ion-linked molecular architectures have been used previously to circumvent difficult and taxing synthetic methods. Here, we demonstrate the growth of metal ion-linked bilayers (ILBs) on monolayer MoS 2 consisting of a first layer spacer (4-mercaptobenzoic acid, MBA) with a Zn(II) ion linked to a fluorophore (BODIPY). Using a combination of Atomic Force Microscopy and Raman spectroscopy, we resolved intrinsic S-vacancies in the MoS 2 lattice via S–H bond breaking of MBA. X-ray Photoelectron Spectroscopy confirmed that Zn(II) acetate can coordinate to carboxylate groups on MBA. Furthermore, with photoluminescence microscopy, we determined that BODIPY emission is observable only in the presence of a metal ion, confirming the growth of a multimolecular ion-linked supramolecular assembly on MoS 2 .

36 MATERIALS SCIENCE↗
DOE OSTI2025

An Investigation of Thermal Properties of 2D Materials [Dissertation]

Studying the thermal conductivity of 2D materials is important due to the applications of 2D materials in fields such as thermal management, thermoelectricity, renewable energy, and sensors. As such, measurements of the thermal conductivity of these 2D materials become important to measure. Thermal conductivity is often difficult to measure for 2D materials due to their atomically thin nature and many experimental methods for doing so requiring contact with the sample, which can alter the thermal properties. A non-contact method for calculating the thermal conductivity of 2D materials supported on substrates in order to model the thermal conductivity of 2D materials for devices, is proposed and experimentally performed in this dissertation. The optothermal Raman technique is a useful non-contact diagnostic technique useful in determining the thermal conductivity of 2D materials. The optothermal Raman typically does not account for heat losses due to convection or radiation or substrate resistance, which are shown to be important factors to consider when developing an optothermal Raman model. Additionally, the calculation of the interfacial thermal conductance between the bottom surface of the sample and the top surface of the substrate, plays an important role in determining the final value of the thermal conductivity of a supported sample, and will yield differing results based on whether or not the conductance is calculated using an approach such as the Diffuse Mismatch Model (DMM) or calculated directly by varying the laser heating profile (usually done by changing the laser objective). This is shown to be the case for both graphene on Ni, graphene on Cu, and SnSe 2 on Cu. In addition to experimentally calculating the thermal conductivity of a 2D material with the optothermal Raman technique, the thermal conductivity of 2D materials can also be calculated using computational methods. The three-phonon method is a method which can be used to simulate phonon scattering processes and determine the thermal conductivity of semiconductors, wherein phonon scattering is the dominant mechanism which determines the thermal conductivity. The three-phonon method uses relaxation times for phonon scattering with other phonons, electrons, and other material system elements, such as isotopes or material defects, in order to create a single-mode relaxation time approximation (SMRTA), which is used to calculate the final value of the thermal conductivity. An important consideration when determining the thermal conductivity of a 2D material using this method is the device geometry, which is reflected in this work as the phonon-boundary scattering relaxation time. This inclusion is important along with the inclusion of phonon-electron scattering in accurately determining the thermal conductivity of a 2D material. In both the optothermal Raman experiments and the three-phonon method computations, strain is shown to have a demonstrable effect on the thermal conductivity of 2D materials. When a 1.1% strain was applied to the mechanical properties of SnSe, the three-phonon processes yielded a lower thermal conductivity than the no-strain case. For the optothermal Raman experiments, the strain induced in the Cu substrate and transferred to a single-layer graphene (SLG) sample yields a trend where the thermal conductivity of the SLG decreases with respect to strain applied. In the case where the interfacial thermal conductance was calculated directly, the conductance increased with respect to strain applied. This presents strain as a reliable and viable method for tuning the thermal properties of 2D materials for device applications.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Reversible Electrochemical Phase Change in Monolayer to Bulk-like MoTe 2 by Ionic Liquid Gating

Transition-metal dichalcogenides (TMDs) exist in various crystal structures with semiconducting, semi-metallic, and metallic properties. The dynamic control of these phases is of immediate interest for next-generation electronics such as phase change memories. Of the binary Mo and W-based TMDs, MoTe 2 is attractive for electronic applications because it has the lowest energy difference (40 meV) between the semiconducting (2H) and semi-metallic (1T') phases, allowing for MoTe 2 phase change by electrostatic doping. Here, we report phase change between the 2H and 1T' polymorphs of MoTe 2 in thicknesses ranging from the monolayer to bulk-like case (73 nm) using an ionic liquid electrolyte at room temperature and in air. We find consistent evidence of a partially reversible 2H-1T' transition using in situ Raman spectroscopy where the phase change occurs in the topmost layers of the MoTe 2 flake. We find a thickness-dependent transition voltage where higher voltages are necessary to drive the phase change for thicker flakes. We also show evidence of electrochemical activity during the gating process by observation of Te metal formation. This finding suggests the formation of Te vacancies which have been reported to lower the energy difference between the 2H and 1T' phases, potentially aiding the phase change process. Furthermore, our discovery that the phase change can be achieved on the surface layer of bulk-like materials reveals that this electrochemical mechanism does not require isolation of a single layer and the effect may be more broadly applicable than previously thought.

2d materials↗
DOE OSTI2025

Millisecond lifetimes and coherence times in 2D transmon qubits

Materials improvement is a powerful approach to reducing loss and decoherence in superconducting qubits, because such improvements can be readily translated to large-scale processors. Recent work improved transmon coherence by using tantalum as a base layer and sapphire as a substrate. The losses in these devices are dominated by two-level systems with comparable contributions from both the surface and bulk dielectrics, indicating that both must be tackled to achieve substantial improvements in the state of the art. Here we show that replacing the substrate with high-resistivity silicon markedly decreases the bulk substrate loss, enabling 2D transmons with time-averaged quality factors (Q avg ) of 9.7 × 10 6 across 45 qubits. For our best qubit, we achieve a Q avg of 1.5 × 10 7 , reaching a maximum Q of 2.5 × 10 7 , corresponding to a lifetime (T 1 ) up to 1.68 ms. This low loss also allows us to observe decoherence effects related to the Josephson junction, and we use an improved, low-contamination junction deposition to achieve Hahn echo coherence times (T 2E ) exceeding T 1 . We achieve these materials improvements without any modifications to the qubit architecture, allowing us to readily incorporate standard quantum control gates. Here, we demonstrate single-qubit gates with 99.994% fidelity. The tantalum-on-silicon platform comprises a simple material stack that can potentially be fabricated at the wafer scale and therefore can be readily translated to large-scale quantum processors.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Temperature-Dependent Optical and Structural Properties of Chiral Two-Dimensional Hybrid Lead-Iodide Perovskites

Layered hybrid halide perovskites gain chirality via the incorporation of chiral organic cations in the spacer layer. These so-called chiral two-dimensional (2D) halide perovskites have attracted considerable interest recently for chiral optoelectronic, spintronic, and ferroelectric applications. However, the effect of temperature on these materials, especially how the structure changes with temperature and its impact on the chiral optoelectronic properties, remains an open question. Here, we study the effect of temperature change on chiral optoelectronic and structural properties through temperature-dependent circularly polarized photoluminescence (CPPL) microscopy and synchrotron powder X-ray diffraction as well as pair distribution function analysis to elucidate the intrinsic chiral optoelectronic and structural variations for R-, S-, and racemic-methylbenzylamine lead iodide. Here our results show that the temperature-induced band gap changes indicate a strong electron–phonon coupling compared to the thermal-induced lattice expansion in chiral 2D perovskites. From powder diffraction measurements, a monotonic lattice expansion is observed on heating with no structural phase transitions over 90–360 K detected for the three samples studied herein. Locally, a strongly anisotropic and even negative expansion in some components of the instantaneous Pb–I pair-distance distribution is suggestive of coupling between dynamical intralayer distortions and lattice expansion. This work provides insights into the fundamental understanding of the temperature effect on chiral optoelectronic and structural properties of chiral 2D perovskites, which can lead to new chiral materials design strategies for future chiral optoelectronic applications.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Modified Dirac Fermions in the Crystalline Xenon and Graphene Moiré Heterostructure

Abstract The interface between two‐dimensional (2D) crystals often forms a Moiré superstructure that imposes a new periodicity, which is a key element in realizing complex electronic phases as evidenced in twisted bilayer graphene. Acombined angle‐resolved photoemission spectroscopy measurements and first‐principles calculations reveal the formation of a Moiré superstructure between a 2D Dirac semi‐metallic crystal, graphene, and a 2D insulating crystal of noble gas, xenon. Incommensurate diffraction pattern and folded Dirac cones around the Brillouin zone center imply the formation of hexagonal crystalline array of xenon atoms. The velocity of Dirac fermions increases upon the formation of the 2D xenon crystal on top of graphene due to the enhanced dielectric screening by the xenon over‐layer. These findings not only provide a novel method to produce a Moiré superstructure from the adsorption of noble gas on 2D materials, but also to control the physical properties of graphene by the formation of a graphene‐noble gas interface.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

The effect of chemically preintercalated alkali ions on the structure of layered titanates and their electrochemistry in aqueous energy storage systems

We introduce a novel chemical preintercalation synthesis technique based on a hydrogen peroxide induced sol–gel process to obtain alkali ion containing ternary layered titanates (MTO, where M = Li, Na, K). Synthesis parameters leading to the formation of single-phase materials with homogeneous elemental distribution are reported for each of the preintercalated ions. Our analyses indicate that the interlayer spacing in the structure of the layered titanates increases with the increase of the radius of the hydrated preintercalated ion. Scanning and transmission electron microscopy imaging revealed morphological diversity: the LTO phase crystallized as nanoplates assembled in “peony-like” spherical agglomerates while NTO and KTO particles exhibited a one-dimensional nanobelt or wire-like morphology, with the KTO nanobelts being shorter and more aggregated than the NTO nanobelts. Structural refinement corroborated by electron diffraction and high-resolution transmission electron microscopy revealed that the structure of the LTO phase is built by stacking Ti–O layers containing a single straight layer of connected TiO 6 octahedra. The layers in NTO and KTO structures form differently and consist of double Ti–O layers with two titanium rows and ragged arrangement of units built by TiO6 octahedra. The NTO electrodes exhibited the highest electrochemical performance in cells with aqueous 1 M Na 2 SO 4 electrolyte, followed by the KTO electrodes and then LTO electrodes, and this trend is maintained at various scan rates. The established relationships between the structure and electrochemical performance reveal that, in addition to interlayer distance and chemistry of the interlayer region, the structure of the layers can play an important role in charge storage properties of layered oxide electrodes. The double Ti–O layers in the structure of NTO and KTO phases provide a larger number of redox centers which could contribute to the superior electrochemical performance as compared to the LTO electrodes. Our findings indicate that layered materials containing double transition metal oxide layers are promising candidates for exfoliation and assembly with electronically conductive layers with the aim to create 2D heterostructures with high electrochemical performance.

25 ENERGY STORAGE↗