Layered Oxide Phases Research Articles

Green strategy for recovering cathode materials from end-of-life lithium-ion batteries using grape pomace

The extraction of critical metals from End-of-life lithium-ion batteries (EOL LIBs) have garnered particular attention for efficient resource recycling. This study provides a method for recycling EOL LIBs using grape pomace (GP) as a reducing agent. The efficacy of this method is demonstrated using LiNixCoyMnzO2 (NCM) cathode material. Kinetic studies suggest that the leaching process of the cathode material in H2SO4 + GP is governed by internal diffusion. The leachate efficiencies of lithium, cobalt, manganese and nickel, surpassed 98 % through manipulation of the thermodynamic conditions. The NCM523 cathode materials are successfully regenerated from the leachate by removing impurities, evaporating and crystallizing, dry ball milling at room temperature and oxidative calcination. Electrochemical data of the regenerated layered oxide phase also showed that the leachate could be upgraded to next-generation materials. This study presents a sustainable with industrial applicability for the large-scale recycling of EOL LIBs.

Na+ orientates Jahn-Teller effect to tune Li+ diffusion pathway and kinetics for Single-Crystal Ni-rich LiNixCoyMn1-x-yO2 cathode materials

Single-crystallization is an effective strategy for enhancing both capacity and stability of Ni-rich LiNi1-x-yCoxMnyO2 (NCM) cathode materials, especially at high cut-off voltages. However, the kinetics limitation of solid-phase Li+ diffusion is a major concern because of the long diffusion path in large single-crystal particles. To address this issue, we synthesize a Na-doped single-crystal LiNi0.82Co0.125Mn0.055O2 (NCM-Na) cathode material by a facile mixed-molten-salt sintering process. Na+ is revealed to be uniformly doped at the Li+ lattice sites within the entire single-crystal particles. This Na+ doping effectively enhances the dynamics of Li+ transport in the layered oxide phases. The NCM-Na material with 2 at.% Na doping shows a Li+ diffusion coefficient up to more than 8 times higher than pristine NCM. In-situ X-ray diffraction and finite element analysis demonstrate significantly facilitated H1-H2-H3 phase transition in NCM-Na materials, compared with the severe phase separation phenomenon in NCM counterpart, hoisting their rate capacity and structure stability. Thus, the NCM-Na material achieves a superior reversible capacity of 177.7 mAh/g at 5C, and a capacity retention of 94.4 % after 100 cycles at 0.5C at a high cut-off voltage of 4.5 V. By density function theory calculations, we reveal that Na+ doping can selectively stabilize the surrounding Li+ at the second farthest hexagonal vertexes by tuning the orientation of the Jahn-Teller effect of Ni3+. These Li+ ions frame a high-speed pathway for preferential Li+ diffusion, which promotes the Li+ diffusion kinetics even in highly delithiated states. Our findings provide insights into the Na+ doping mechanism and present a low-cost, highly efficient, and scalable method to enhance the performance of single-crystal Ni-rich NCM materials.

Mitigating kinetic hindrance of single-crystal Ni-rich cathodes through morphology modulation, nickel reduction, and lithium vacancy generation achieved by terbium doping

Single crystallization has proven to be effective in enhancing the capacity and stability of Ni-rich LiNi1−x−yCoxMnyO2 (SNCM) cathode materials, particularly at high cut-off voltages. Nevertheless, the synthesis of high-quality single-crystal particles remains challenging because of severe particle agglomeration and irregular morphologies. Moreover, the limited kinetics of solid-phase Li+ diffusion pose a significant concern because of the extended diffusion path in large single-crystal particles. To address these challenges, we developed a Tb-doped single-crystal LiNi0.83Co0.11Mn0.06O2 (SNCM-Tb) cathode material using a straightforward mixed molten salt sintering process. The Tb-doped Ni-rich single crystals presented a quasi-spherical morphology, which is markedly different from those reported in previous studies. Tb4+ doping significantly enhanced the dynamic transport of Li+ ions in the layered oxide phase by reducing the Ni valence state and creating Li vacancies. A SNCM-Tb material with 1 at% Tb doping shows a Li+ diffusion coefficient up to more than 9 times higher than pristine SNCM in the non-diluted state. In situ X-ray diffraction analysis demonstrated a significantly facilitated H1-H2-H3 phase transition in the SNCM-Tb materials, thereby enhancing their rate capacity and structural stability. SNCM-Tb exhibited a reversible capacity of 186.9 mA h g−1 at 5 C, retaining 94.6% capacity after 100 cycles at 0.5 C under a 4.5 V cut-off. Our study elucidates the Tb4+ doping mechanisms and proposes a scalable method for enhancing the performance of single-crystal Ni-rich NCM materials.

Promotion of the Nucleation of Ultrafine Ni-Rich Layered Oxide Primary Particles by an Atomic Layer-Deposited Thin Film for Enhanced Mechanical Stability.

Understanding the atomistic mechanisms of non-equilibrium processes during solid-state synthesis, such as nucleation and grain structure formation of a layered oxide phase, is a critical challenge for developing promising cathode materials such as Ni-rich layered oxide for Li-ion batteries. In this study, we found that the aluminum oxide coating layer transforms into lithium aluminate as an intermediate, which has favorable low interfacial energies with the layered oxide to promote the nucleation of the latter. The fast and uniform nucleation and formation of the layered oxide phase at relatively low temperatures were evidenced using solid-state nuclear magnetic resonance and in situ synchrotron X-ray diffraction. The resulting Ni-rich layered oxide cathode has fine primary particles, as visualized by three-dimensional tomography constructed using a focused-ion beam and scanning electron microscopy. The densely packed fine primary particles enable the excellent mechanical strength of the secondary particles, as demonstrated by in situ compression tests. This strategy provides a new approach for developing next-generation, high-strength battery materials.

Recent Advances for High-Entropy based Layered Cathodes for Sodium Ion Batteries.

In recent years, layered oxides have been extensively studied as promising cathode materials for sodium ion batteries. However, layered oxides undergo complex phase transitions during charge-discharge process, which adversely affects the electrochemical performance. High-entropy layered oxides as a unique design concept can effectively improve the cycling performance of cathode materials by virtue of the 2D ion migration channels between the layers. Based on the concepts of high-entropy and layered oxides, this paper reviews the research status of high-entropy layered oxides in the field of sodium-ion batteries, focusing on the connection between high-entropy and layered oxide phase transitions during electrochemical charging and discharging. Finally, the advantages of layered cathode materials based high-entropy are summarized, and the opportunities and challenges of future high-entropy layered materials are proposed.

Influence of Morphology and Compositional Mixing on the Electrochemical Performance of Li-Rich Layered Oxides Derived from Nanoplatelet-Shaped Transition Metal Oxide–Hydroxide Precursors

The influence of morphology and compositional mixing on the electrochemical performances of Li-rich layered oxides (LLOs), specifically to address the high rate capability, is investigated. LLOs of composition xLi2MnO3·(1 – x)LiMn0.25Ni0.38Co0.37O2 (LMNC, x = 0, 0.2, 0.4, and 0.6), lying in the plane NMC(640)–LCO–LMO, are synthesized in nanoplatelet morphology, and the results are compared to the same compounds prepared by a conventional solid-state reaction (SSR). Hexagonal-shaped thin (∼50 nm) flakes of transition metal oxide–hydroxide [TMO(OH)], prepared by the hydrothermal process, are reacted with Li carbonate to derive nanoplatelet morphology of LMNC by topotactic conversion. Structural and compositional evolutions of LLOs are analyzed with Rietveld refinement. The composite nature of LMNC comprising of monoclinic Li2MnO3 and rhombohedral LiMO2 phases is evidenced. High-resolution transmission electron microscopy studies show the existence of a monoclinic Li2MnO3 phase embedded within the rhombohedral layered oxide phase. A uniform compositional distribution of all elements is discerned from EDS mapping, strongly suggesting that metal cations in both TMO/OH and LMNC are highly intermixed. Electrochemical properties become better with the larger fraction of the Li2MnO3 phase in LiMO2. Among four compositions examined, LMNC (x = 0.6) shows the best electrochemical performance, with a capacity of ∼240 mAh g–1 (∼173 mAh g–1) at 0.1 C (1 C) current rate. Cycling stability studies, carried out at 1 C rate for 100 cycles, show a high capacity retention of 86%. Capacity at 3 C (5 C) is ∼140 mAh g–1 (∼80 mAh g–1) in LMNC (x = 0.6). LMNC (x = 0 and 0.6) prepared by SSR show inferior properties, suggesting that morphology and thorough intermixing of monoclinic Li2MnO3 and rhombohedral LiMO2 phases are shown to play a significant role. Although enhanced performance is generally attributed to the extra capacity contribution from the Li2MnO3 phase, this study unequivocally brings out the influence of morphology on the electrochemical properties.

Frontispiece: Metal Oxide Nanosheets as 2D Building Blocks for the Design of Novel Materials

Two-dimensional metal oxide nanocrystals are often made by a chemical delamination process in water, which involves a layered oxide phase as the starting material. The exfoliated nanosheets have aspect ratios comparable with that of a paper sheet, and they are also very flexible. Oxide nanosheets can be used as building blocks for the construction of improved or entirely new functional materials for a wide range of application areas: nanoelectronics, energy storage, catalysis and tribology, to name just a few. For more details see the Review by J. E. ten Elshof et al. on page 9084 ff.

Comprehensive study of a versatile polyol synthesis approach for cathode materials for Li-ion batteries

This work reports a comprehensive study of a novel polyol method that can successfully synthesize layered LiNi0.4Mn0.4Co0.2O2, spinel LiNi0.5Mn1.5O4, and olivine LiCoPO4 cathode materials. When properly designed, polyol method offers many advantages such as low cost, ease of use, and proven scalability for industrial applications. Most importantly, the unique properties of polyol solvent allow for greater morphology control as shown by all the resulting materials exhibiting monodispersed nanoparticles morphology. This morphology contributes to improved lithium ion transport due to short diffusion lengths. Polyol-synthesized LiNi0.4Mn0.4Co0.2O2 delivers a reversible capacity of 101 and 82 mAh·g−1 using high current rate of 5C and 10C, respectively. It also displays surprisingly high surface structure stability after charge-discharge processes. Each step of the reaction was investigated to understand the underlying polyol synthesis mechanism. A combination of in situ and ex situ studies reveal the structural and chemical transformation of Ni-Co alloy nanocrystals overwrapped by a Mn- and Li-embedded organic matrix to a series of intermediate phases, and then eventually to the desired layered oxide phase with a homogeneous distribution of Ni, Co, and Mn. We envisage that this type of analysis will promote the development of optimized synthesis protocols by establishing links between experimental factors and important structural and chemical properties of the desired product. The insights can open a new direction of research to synthesize high-performance intercalation compounds by allowing unprecedented control of intermediate phases using experimental parameters.

Sr2FeIrO4: Square-Planar Ir(II) in an Extended Oxide.

Topochemical reduction of the double-perovskite oxide Sr2FeIrO6 under dilute hydrogen leads to the formation of Sr2FeIrO4. This phase consists of ordered infinite sheets of apex-linked Fe2+O4 and Ir2+O4 squares stacked with Sr2+ cations and is the first report of Ir2+ in an extended oxide phase. Plane-wave density functional theory calculations indicate high-spin Fe2+ (d6, S = 2) and low-spin Ir2+ (d7, S = 1/2) configurations for the metals and confirm that both ions have a doubly occupied d z2 orbital, a configuration that is emerging as a consistent feature of all layered oxide phases of this type. The stability and double occupation of d z2 in the Ir2+ ions invites a somewhat unexpected analogy to the extensively studied Ir4+ ion as both ions share a common near-degenerate (d xy/ xz/ yz)5 valence configuration. On cooling below 115 K, Sr2FeIrO4 enters a magnetically ordered state in which the Ir and Fe sublattices adopt type II antiferromagnetically coupled networks which interpenetrate each other, leading to frustration in the nearest-neighbor Fe-O-Ir couplings, half of which are ferromagnetic and half antiferromagnetic. The spin frustration drives a symmetry-lowering structural distortion in which the four equivalent Ir-O and Fe-O distances of the tetragonal I4/ mmm lattice split into two mutually trans pairs in a lattice with monoclinic I112/ m symmetry. This strong magneto-lattice coupling arises from the novel local electronic configurations of the Fe2+ and Ir2+ cations and their cation-ordered arrangement in a distorted perovskite lattice.

Electrochemical performance of novel O3 layered Al,Mg doped titanates as anode materials for Na-ion batteries

The synthesis and the electrochemical behavior of Al,Mg-doped NayTiO2, i.e. (Nay [Ti(1−x)Alx]O2, 0.05≤x≤0.40, and Nay [Ti(1−x)Mgx]O2, 0.15≤x≤0.35) layered oxide phases as potential anodes for Na-ion batteries have been investigated. They were synthesized by solid state route with controlled sodium vapor pressure in inert atmosphere. The study of the crystal structure by XRD revealed that a maximum of 10% Al and 15% Mg were doped in the O3-type structure without important structural changes associated with the replacement of Ti by Al/Mg ion. 23Na solid state NMR measurements were performed to confirm the Mg doping, its effects on the local structure, and the disordered disposition of Mg in the compound. The synthesized phases were electrochemically active at low voltages (1.6–0.08V vs. Na+/Na). The high Mg-doped phase demonstrated improved high rate performance and a capacity of 107mAhg−1 at C/20 rate with a voltage profile smoother than the undoped material.

Facile Synthesis of Platelike Hierarchical Li1.2Mn0.54Ni0.13Co0.13O2 with Exposed {010} Planes for High-Rate and Long Cycling-Stable Lithium Ion Batteries.

Lithium-rich layered oxides are promising cathode candidates for the production of high-energy and high-power electronic devices with high specific capacity and high discharge voltage. However, unstable cycling performance, especially at high charge-recharge rate, is the most challenge issue which needs to be solved to foster the diffusion of these materials. In this paper, hierarchical platelike Li1.2Mn0.54Ni0.13Co0.13O2 cathode materials were synthesized by a facile solvothermal method followed by calcination. Calcination time was found to be a key parameter to obtain pure layered oxide phase and tailor its hierarchical morphology. The Li-rich material consists of primary nanoparticles with exposed {010} planes assembled to form platelike layers which exhibit low resistance to Li+ diffusion. In detail, the product by calcination at 900 °C for 12 h exhibits specific capacity of 228, 218, and 204 mA h g-1 at 200, 400, and 1000 mA g-1, respectively, whereas after 100 cycles at 1000 mA g-1 rate of charge and recharge the specific capacity was retained by about 91%.

Phase and structural transformations in annealed copper coatings in relation to oxide whisker growth

We describe structural and phase transformation in copper coatings made of microparticles during heating and annealing in air in the temperature range up to 400°C. Such thermal treatment is accompanied by intensive CuO nanowhisker growth on the coating surface and the formation of the layered oxide phases (Cu2O and CuO) in the coating interior. X-ray diffraction and focused ion beam (FIB) are employed to characterize the multilayer structure of annealed copper coatings. Formation of volumetric defects such as voids and cracks in the coating is demonstrated.

Stability of Ruddlesden–Popper-structured oxides in humid conditions

Some of layered transition-metal oxides are known to react with atmospheric humidity to form through topotactic intercalation reactions new water-containing layered structures. Here we investigate the influence of oxygen content (7−δ) of the Ruddlesden–Popper-structured Sr{sub 3}FeMO{sub 7−δ} (M=Ni, Mn, Ti) oxides on the water-intercalation reaction. It is found that their oxygen contents influence greatly the reactivity of the phases with water. Other factors possibly affecting the reactivity are discussed on the basis of the present data in combination with a comprehensive review of previous works on Ruddlesden–Popper and related layered oxide phases. - Graphical abstract: Many of the Ruddlesden–Popper-structured A{sub 3}B{sub 2}O{sub 7−δ} oxides readily react with water via intercalation reactions. Three possible factors affecting the water intercalation are identified: oxygen content of the phase, ionic radius of cation A and valence state of cation B. The resultant layered water-derivative phases can be categorised into two groups, depending on the crystal symmetry of the phase. Highlights: • Ruddlesden–Popper oxides A{sub 3}B{sub 2}O{sub 7−δ} often accommodate water via intercalation reaction. • The lower the oxygen content 7−δ is the more readily the intercalation reaction occurs. • The second factor promoting the reaction is the large size of cation A. • Themore » third possible factor is the high valence state of cation B. • Resultant water-derivatives can be categorised into two groups depending on symmetry.« less

The significant effect of the phase composition on the oxygen reduction reaction activity of a layered oxide cathode

Layered oxides of Sr4Fe4Co2O13 (SFC2) which contains alternating perovskite oxide octahedral and polyhedral oxide double layers are attractive for their mixed ionic and electronic conducting and oxygen reduction reaction properties. In this work, we used the EDTA–citrate synthesis technique to prepare SFC2 and vary the calcination temperature between 900 and 1100 °C to obtain SFC2, containing different phase content of perovskite (denoted as SFC-P) and (Fe,Co) layered oxide phases (SFC-L). Rietveld refinements show that the SFC-P phase content increased from ∼39 wt% to ∼50 wt% and ∼61 wt% as the calcination temperature increased from 900 °C (SFC2-900) to 1000 °C (SFC2-1000) and 1050 °C (SFC2-1050). At 1100 °C (SFC2-1100), SFC-P became the dominant phase. The oxygen transport properties (e.g. oxygen chemical diffusion coefficient and oxygen permeability), electrical conductivity and oxygen reduction reaction activity is enhanced in the order of SFC2-1000, SFC2-1100 and SFC2-1050. The trend established here therefore negates the hypothesis that the perovskite phase content correlates with the oxygen transport property enhancement. The results suggest instead that there is an optimum composition value (e.g. 61 wt% of SFC-L for SFC2-1050 in this work) on which synergistic effects take place between the SFC-P and SFC-L phase.

Hydrotalcite-like layered bismuth–iodine–oxides as waste forms

Abstract The effective capture and storage of radiological I (129I) remains a significant concern for safe nuclear waste storage and safe nuclear energy. Due to its long half-life (1.6 × 107 a) and concerns for involvement in human metabolic processes, durable waste forms are of great interest and research focus. Long term durability is mimicked in geological analogs. As a result, the authors have utilizing a facile, in situ process of synthesizing mineral analogs of layered (hydrotalcite-like) bismuth–iodine–oxide waste forms that does not require advanced separation and isolation of the I species from the aqueous solution. Specifically, the phases are crystallized and precipitated out of the waste stream at room temperature by the simple titration of an acidified Bi nitrate solution which precipitates layered oxide phases; phase composition and I weight loading is determined by the Bi:I ratio in solution. Products are designed to combine high I loading levels with chemical durability. Several characterization techniques were employed to better understand the relationship between waste forms, their abilities to encapsulate I, and their stability under possible repository conditions. They include solubility leach testing with elevated levels of common ground water anions Cl - , HCO 3 - , SO 4 2 - , thermal stability testing, elemental analysis, X-ray diffraction and microscopy studies.

Morphology, structure, and nucleation of out-of-phase boundaries (OPBs) in epitaxial films of layered oxides

Out-of-phase boundaries (OPBs) are translation boundary defects characterized by a misregistry of a fraction of a unit cell dimension in neighboring regions of a crystal. Although rarely observed in the bulk, they are common in epitaxial films of complex crystals due to the physical constraint of the underlying substrate and a low degree of structural rearrangement during growth. OPBs can strongly affect properties, but no extensive studies of them are available. The morphology, structure, and nucleation mechanisms of OPBs in epitaxial films of layered complex oxides are presented with a review of published studies and new work. Morphological trends in two families of layered oxide phases are described. The atomic structure at OPBs is presented. OPBs may be introduced into a film during growth via the primary mechanisms that occur at film nucleation (steric, nucleation layer,a-bmisfit, and inclined-cmisfit) or after growth via the secondary nucleation mechanism (crystallographic shear in response to loss of a volatile component). Mechanism descriptions are accompanied by experimental examples. Alternative methods to the direct imaging of OPBs are also presented.

Mixed Layered Oxide Phases NaxLi1‐xNiO2: A Detailed Description of Their Preparation and Structural and Magnetic Identification.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Mixed layered oxide phases Na xLi 1− xNiO 2: a detailed description of their preparation and structural and magnetic identification

The mixed layered oxide phases Na x Li 1− x NiO 2 were prepared and characterised by X-ray diffraction, chemical analysis and a thorough magnetic study. Single phase compounds were obtained for the nominal compositions 0 ⩽ x ⩽ 0.3 and 0.8 ⩽ x ⩽ 1.0 . The chemical analysis reveals that only up to 6% of sodium can actually be substituted for lithium in the lithium-rich samples, and that heavy nickel substitution for lithium occurs simultaneously (up to 7%). The magnetic susceptibility data confirm this and clearly show the ferromagnetic coupling between the nickel layers, which is caused by the disordered Ni 2+ ions. On the sodium-rich side the perfect layering of NaNiO 2 is maintained upon the substitution of lithium for sodium, the chemical analysis shows that up to 30% of lithium can be substituted for sodium. The lithium-rich compounds crystallise in the α-NaFeO 2-structure (space group R-3m), the most sodium-rich compounds adopt the structure type of NaNiO 2 (space group C2/m), whereas, around the composition Na 0.7Li 0.3NiO 2 (nominal composition “Na 0.8Li 0.2NiO 2”), a second (R-3m)-type structure is formed with increased lattice parameters, when compared to LiNiO 2. We show that when the lithium substitution for sodium is small, the antiferromagnetism and the Jahn–Teller transition of NaNiO 2 are only marginally affected, but when the nominal Na 0.8-composition is reached, the Jahn–Teller transition completely disappears and both the saturation and spin-flop fields are changed.

Synthesis and Structural Characterization of a New Family of Layered Intergrowth Phases Based on Antimony(III) Oxide

A new family of layered oxide phases, described by the general formula SbIIInSbVxAn−xTiO4n+2forn= 1, 2, 3 (A= Ta) andn= 1, 3 (A= Nb) is reported. Models for the structures of then= 1 andn= 2 members are presented, based on the previously reportedn= 3 structures, XRD, electron diffraction, and microanalytical data. The structures of all members are described as ordered intergrowths of lamellae of the primary oxides of SbIIIand SbV. The other metal atoms are incorporated into lamellae analogous to structures formed by their own primary oxides or binary oxides with SbIII. The structural features of layered antimony oxides as a group, including Sb2WO6and Sb2MoO6, are discussed. Antimony oxide-based analogs of the bismuth oxide-based Aurivillius phases appear not to exist in the Sb2O3–TiO2–Nb2O5, Sb2O3–TiO2–Ta2O5, or related systems.