Improved Voltage and Cycling for Li+ Intercalation in High-Capacity Disordered Oxyfluoride Cathodes.
Ontology highlight
ABSTRACT:
SUBMITTER: Ren S
PROVIDER: S-EPMC5115328 | biostudies-literature | 2015 Oct
REPOSITORIES: biostudies-literature
Publications
Improved Voltage and Cycling for Li<sup>+</sup> Intercalation in High-Capacity Disordered Oxyfluoride Cathodes.
Ren Shuhua S Chen Ruiyong R Maawad Emad E Dolotko Oleksandr O Guda Alexander A AA Shapovalov Viktor V Wang Di D Hahn Horst H Fichtner Maximilian M
Advanced science (Weinheim, Baden-Wurttemberg, Germany) 20150612 10
<b>New high-capacity intercalation cathodes</b> of Li<sub>2</sub>V <i><sub>x</sub></i> Cr<sub>1-<i>x</i></sub> O<sub>2</sub>F with a stable disordered rock salt host framework allow a high operating voltage up to 3.5 V, good rate performance (960 Wh kg<sup>-1</sup> at ≈1 C), and cycling stability. ...[more]
Similar Datasets
Project description:Promising theoretical capacities and high voltages are offered by Li-rich disordered rocksalt oxyfluoride materials as cathodes in lithium-ion batteries. However, as has been discovered for many other Li-rich materials, the oxyfluorides suffer from extensive surface degradation, leading to severe capacity fading. In the case of Li2VO2F, we have previously determined this to be a result of detrimental reactions between an unstable surface layer and the organic electrolyte. Herein, we present the protection of Li2VO2F particles with AlF3 surface modification, resulting in a much-enhanced capacity retention over 50 cycles. While the specific capacity for the untreated material drops below 100 mA h g-1 after only 50 cycles, the treated materials retain almost 200 mA h g-1. Photoelectron spectroscopy depth profiling confirms the stabilization of the active material surface by the surface modification and reveals its suppression of electrolyte decomposition.
| S-EPMC7493205 | biostudies-literature
Project description:Disordered rocksalt (DRX) materials are an emerging class of cathode materials for Li ion batteries. Their advantages include better sustainability through wider choices of transition metal (TM) elements in the materials and higher theoretical capacities due to the redox reaction contributions from both the TM and O elements compared with state-of-the-art cathode materials. However, the realisable capacities of the DRX materials need to be improved as their charge transport kinetics and cycling stability are still poor. Here, Li1.2Mn0.4Ti0.4O2 (LMTO) and Li1.3Mn0.4Ti0.3O1.7F0.3 (LMTOF) are synthesised with abundant TMs of Mn and Ti only. Three approaches of partial substitution of O with F, reducing particle size and C coating on the particle surface are used simultaneously to improve realisable capacity, rate capability and stability. We rationalise that the improved electrochemical performance is due to the improved short and long range Li+ diffusion kinetics, electrical conductivity and reduced O loss. These strategies can also be applicable to a variety of DRX materials to improve performance.
| S-EPMC10560877 | biostudies-literature
Project description:In this work, we synthesized 1D hollow square rod-shaped MnO2, and then obtained Na+ lattice doped-oxygen vacancy lithium-rich layered oxide by a simple molten salt template strategy. Different from the traditional synthesis method, the hollow square rod-shaped MnO2 in NaCl molten salt provides numerous anchor points for Li, Co, and Ni ions to directly prepare Li1.2Ni0.13Co0.13Mn0.54O2 on the original morphology. Meanwhile, Na+ is also introduced for lattice doping and induces the formation of oxygen vacancy. Therefrom, the modulated sample not only inherits the 1D rod-like morphology but also achieves Na+ lattice doping and oxygen vacancy endowment, which facilitates Li+ diffusion and improves the structural stability of the material. To this end, transmission electron microscopy, high-angle annular dark-field scanning transmission electron microscopy, X-ray photoelectron spectroscopy, and other characterization are used for analysis. In addition, density functional theory is used to further analyze the influence of oxygen vacancy generation on local transition metal ions, and theoretically explain the mechanism of the electrochemical performance of the samples. Therefore, the modulated sample has a high discharge capacity of 282 mAh g-1 and a high capacity retention of 90.02% after 150 cycles. At the same time, the voltage decay per cycle is only 0.0028 V, which is much lower than that of the material (0.0038 V per cycle) prepared without this strategy. In summary, a simple synthesis strategy is proposed, which can realize the morphology control of Li1.2Ni0.13Co0.13Mn0.54O2, doping of Na+ lattice, and inducing the formation of oxygen vacancy, providing a feasible idea for related exploration.
| S-EPMC10179001 | biostudies-literature
Project description:In the search for high energy density cathodes for next-generation lithium-ion batteries, the disordered rocksalt oxyfluorides are receiving significant attention due to their high capacity and lower voltage hysteresis compared with ordered Li-rich layered compounds. However, a deep understanding of these phenomena and their redox chemistry remains incomplete. Using the archetypal oxyfluoride, Li2MnO2F, we show that the oxygen redox process in such materials involves the formation of molecular O2 trapped in the bulk structure of the charged cathode, which is reduced on discharge. The molecular O2 is trapped rigidly within vacancy clusters and exhibits minimal mobility unlike free gaseous O2, making it more characteristic of a solid-like environment. The Mn redox process occurs between octahedral Mn3+ and Mn4+ with no evidence of tetrahedral Mn5+ or Mn7+. We furthermore derive the relationship between local coordination environment and redox potential; this gives rise to the observed overlap in Mn and O redox couples and reveals that the onset potential of oxide ion oxidation is determined by the degree of ionicity around oxygen, which extends models based on linear Li-O-Li configurations. This study advances our fundamental understanding of redox mechanisms in disordered rocksalt oxyfluorides, highlighting their promise as high capacity cathodes.
| S-EPMC7872422 | biostudies-literature
Project description:Development of high-performance aqueous batteries is an important goal for energy sustainability owing to their environmental benignity and low fabrication costs. Although a layered vanadyl phosphate is one of the most-studied host materials for intercalation electrodes with organic electrolytes, little attention has been paid to its use in aqueous Li+ systems because of its excessive dissolution in water. Herein, by controlling the water concentration, we demonstrate the stable operation of a layered vanadyl phosphate electrode in an aqueous Li+ electrolyte. The combination of experimental analyses and density functional theory calculations reveals that reversible (de)lithiation occurs between dehydrated phases, which can only exist in an optimal water concentration.
| S-EPMC8179479 | biostudies-literature
Project description:Alkali ion intercalation is fundamental to battery technologies for a wide spectrum of potential applications that permeate our modern lifestyle, including portable electronics, electric vehicles, and the electric grid. In spite of its importance, the Nernstian nature of the charge transfer process describing lithiation of carbon has not been described previously. Here we use the ultrathin few-layer graphene (FLG) with micron-sized grains as a powerful platform for exploring intercalation and co-intercalation mechanisms of alkali ions with high versatility. Using voltammetric and chronoamperometric methods and bolstered by density functional theory (DFT) calculations, we show the kinetically facile co-intercalation of Li+ and K+ within an ultrathin FLG electrode. While changes in the solution concentration of Li+ lead to a displacement of the staging voltammetric signature with characteristic slopes ca. 54-58 mV per decade, modification of the K+/Li+ ratio in the electrolyte leads to distinct shifts in the voltammetric peaks for (de)intercalation, with a changing slope as low as ca. 30 mV per decade. Bulk ion diffusion coefficients in the carbon host, as measured using the potentiometric intermittent titration technique (PITT) were similarly sensitive to solution composition. DFT results showed that co-intercalation of Li+ and K+ within the same layer in FLG can form thermodynamically favorable systems. Calculated binding energies for co-intercalation systems increased with respect to the area of Li+-only domains and decreased with respect to the concentration of -K-Li- phases. While previous studies of co-intercalation on a graphitic anode typically focus on co-intercalation of solvents and one particular alkali ion, this is to the best of our knowledge the first study elucidating the intercalation behavior of two monovalent alkali ions. This study establishes ultrathin graphitic electrodes as an enabling electroanalytical platform to uncover thermodynamic and kinetic processes of ion intercalation with high versatility.
| S-EPMC8179004 | biostudies-literature
Project description:Lithium-oxygen batteries with high theoretical energy densities have great potential. Recent studies have focused on different cathode architecture design to address poor cycling performance, while the impact of interface stability on cathode side has been barely reported. In this study, we introduce CoO mesoporous spheres into cathode, where the growth of crystalline discharge products (Li2O2) is directly observed on the CoO surface from aberration-corrected STEM. This CoO based cathode demonstrates more than 300 discharge/charge cycles with excessive lithium anode. Under deep discharge/charge, CoO cathode exhibited superior cycle performance than that of Co3O4 with similar nanostructure. This improved cycle performance can be ascribed to a more favorable adsorption configuration of Li2O2 intermediates (LiO2) on CoO surface, which is demonstrated through DFT calculation. The favorable adsorption of LiO2 plays an important role in the enhanced cycle performance, which reduced the contact of LiO2 to carbon materials and further alleviated the side reactions during charge process. This compatible interface design may provide an effective approach in protecting carbon-based cathodes in metal-oxygen batteries.
| S-EPMC4342555 | biostudies-literature
Project description:Here we show that dendritic architectures are attractive as the basis of hierarchically structured battery electrodes. Dendritically structured FeS2, synthesized via simple thermal sulfidation of electrodeposited dendritic α-Fe, was formed into an electrode and cycled vs. lithium. The reversible capacities of the dendritic FeS2 cathode were 560 mA h g-1 at 0.5C and 533 mA h g-1 at 1.0C after 50 cycles over 0.7-3.0 V. Over 0.7-2.4 V, where the electrode is more stable, the reversible capacities are 348 mA h g-1 at 0.2C and 179 mA h g-1 at 1.0C after 150 cycles. The good cycling performance and high specific capacities of the dendritic FeS2 cathodes are attributed to the ability of a dendritic structure to provide good ion and electron conducting pathways, and a large surface area. Importantly, the dendritic structure appears capable of accommodating volume changes imposed by the lithiation and delithiation process. The presence of a Li2-x FeS2 phase is indicated for the first time by high-resolution transmission electron microscopy (HRTEM) and scanning transmission electron microscopy (STEM) electron energy loss spectroscopy (EELS). We suspect this phase is what enables electrochemical cycling to possess high reversibility over 0.7-2.4 V.
| S-EPMC9090669 | biostudies-literature
Project description:Oxygen release and irreversible cation migration are the main causes of voltage fade in Li-rich transition metal oxide cathode. But their correlation is not very clear and voltage decay is still a bottleneck. Herein, we modulate the oxygen anionic redox chemistry by constructing Li2ZrO3 slabs into Li2MnO3 domain in Li1.21Ni0.28Mn0.51O2, which induces the lattice strain, tunes the chemical environment for redox-active oxygen and enlarges the gap between metallic and anionic bands. This modulation expands the region in which lattice oxygen contributes capacity by oxidation to oxygen holes and relieves the charge transfer from anionic band to antibonding metal-oxygen band under a deep delithiation. This restrains cation reduction, metal-oxygen bond fracture, and the formation of localized O2 molecule, which fundamentally inhibits lattice oxygen escape and cation migration. The modulated cathode demonstrates a low voltage decay rate (0.45 millivolt per cycle) and a long cyclic stability.
| S-EPMC8144552 | biostudies-literature
Project description:Large lattice expansion/contraction with Li+ intercalation/deintercalation of electrode active materials results in severe structural degradation to electrodes and can negatively impact the cycle life of solid-state lithium-based batteries. In case of the layered orthorhombic MoO3 (α-MoO3), its large lattice variation along the b axis during Li+ insertion/extraction induces irreversible phase transition and structural degradation, leading to undesirable cycle life. Herein, we propose a lattice pinning strategy to construct a coherent interface between α-MoO3 and η-Mo4O11 with epitaxial intergrowth structure. Owing to the minimal lattice change of η-Mo4O11 during Li+ insertion/extraction, η-Mo4O11 domains serve as pin centers that can effectively suppress the lattice expansion of α-MoO3, evidenced by the noticeably decreased lattice expansion from about 16% to 2% along the b direction. The designed α-MoO3/η-Mo4O11 intergrown heterostructure enables robust structural stability during cycling (about 81% capacity retention after 3000 cycles at a specific current of 2 A g-1 and 298 ± 2 K) by harnessing the merits of epitaxial stabilization and the pinning effect. Finally, benefiting from the stable positive electrode-solid electrolyte interface, a highly durable and flexible all-solid-state thin-film lithium microbattery is further demonstrated. This work advances the fundamental understanding of the unstable structure evolution for α-MoO3, and may offer a rational strategy to develop highly stable electrode materials for advanced batteries.
| S-EPMC10589268 | biostudies-literature