Search

Ni‐rich layered oxides are strong candidates for next–generation high‐energy batteries. Unlike batteries in typical laboratory settings, batteries in practical applications are generally not discharged immediately upon reaching a fully charged state, but instead, remain there for varying periods of time before usage. Such a state places immense electrochemical stress on the cathode as much of the Ni‐rich layered oxide degradation mechanisms occur at the highly charged/delithiated state. Differentiating between lab and practical use cases, it is shown for Li[Ni0.90Co0.05Mn0.05]O2 that even the introduction of a short dwell period at the highly charged state leads to substantial differences in cycling performance (capacity retention of 89.4% vs 37.5% at the 100th cycle with or without dwelling, respectively). To overcome the rapid deterioration at high voltage, antimony is used as a dopant to reduce the lattice instability of the high Ni layer structure, especially at the grain boundaries regions, where degradation concentrates at the cathode‐electrolyte interfaces. The resulting Li[Ni0.895Co0.05Mn0.05Sb0.05]O2 cathode material not only maintains stability during extended dwelling periods at the charged state, but also accommodates superior fast‐charge capabilities. [ABSTRACT FROM AUTHOR]

The article examines the possible developments regarding mental health services in Great Britain. There will be new providers of mental health services with the possible emergence of different kinds of services. Mental health foundation trusts will probably have to compete with new service providers on price and quality. A report by economist Richard Layard has stressed the economic impact of mental illness, particularly with regards to those with relatively minor conditions of anxiety and depression.

The effect of relative density on the hardness and fracture toughness of Al-substituted cubic garnet Li6.19 Al0.27 La3 Zr2 O12 ( LLZO) was investigated. Polycrystalline LLZO was made using solid-state synthesis and hot-pressing. The relative density was controlled by varying the densification time at fixed temperature (1050°C) and pressure (62 MPa). After hot-pressing, the average grain size varied from approximately 2.7-3.7 μm for the 85% and 98% relative density samples, respectively. Examination of fracture surfaces revealed a transition from inter- to intragranular fracture as the relative density increased. The Vickers hardness increased with relative density up to 96%, above which the hardness was constant. At 98% relative density, the Vickers hardness was equal to the hardness measured by nanoindentation 9.1 GPa, which is estimated as the single-crystal hardness value. An inverse correlation between relative density and fracture toughness was observed. The fracture toughness increased linearly from 0.97 to 2.37 MPa√m for the 98% and 85% relative density samples, respectively. It is suggested that crack deflection along grain boundaries can explain the increase in fracture toughness with decreasing relative density. It was also observed that the total ionic conductivity increased from 0.0094 to 0.34 mS/cm for the 85%-98% relative density samples, respectively. The results of this study suggest that the microstructure of LLZO must be optimized to maximize mechanical integrity and ionic conductivity. [ABSTRACT FROM AUTHOR]

Rechargeable Zn metal batteries (RZMBs) may provide a more sustainable and lower-cost alternative to established battery technologies in meeting energy storage applications of the future. However, the most promising electrolytes for RZMBs are generally aqueous and require high concentrations of salt(s) to bring efficiencies toward commercially viable levels and mitigate water-originated parasitic reactions including hydrogen evolution and corrosion. Electrolytes based on nonaqueous solvents are promising for avoiding these issues, but full cell performance demonstrations with solvents other than water have been very limited. To address these challenges, we investigated MeOH as an alternative electrolyte solvent. These MeOH-based electrolytes exhibited exceptional Zn reversibility over a wide temperature range, with a Coulombic efficiency > 99.5% at 50% Zn utilization without cell short-circuit behavior for > 1,800 h. More important, this remarkable performance translates well to Zn ∥ metal-free organic cathode full cells, supporting < 6% capacity decay after > 800 cycles at -40 °C. [ABSTRACT FROM AUTHOR]

Abstract: The garnet-type ceramic electrolyte of nominal composition Li7La3Zr2O12 can exist in the tetragonal and cubic form. This article investigates the tetragonal to cubic phase transition based on super-valent cation substitution on the 24c site typically occupied by La (3+) in the garnet structure. Ce (4+) was selected as the super-valent cation represented as x in Li7−x La3−x Ce x Zr2O12. The doping study showed that cubic LLZO was stabilized for Ce ≥ 0.2. These data agree with most literature reports suggesting that the creation of Li vacancies, while maintaining oxygen stoichiometry, is necessary to stabilize cubic LLZO. Moreover, this work suggests a critical Li vacancy concentration (0.12–0.4 mol per mole of Li7La3Zr2O12) is necessary to stabilize cubic LLZO. While the addition of Ce stabilized cubic LLZO, the total ionic conductivity (0.014 mS cm−1) was considerably lower compared to Al and Ta doped LLZO (0.4–0.9 mS cm−1, respectively). The lower conductivity is likely due to CeO2 precipitation at grain boundaries. [Copyright &y& Elsevier]

Abstract: Hot-pressing at 1050°C lead to near theoretical density (∼98% relative density) tetragonal LLZO. The total conductivity value for dense tetragonal LLZO is ∼2.3×10−5 Scm−1. This is the highest reported value for tetragonal LLZO. This vast improvement in total conductivity is a result of the higher density achieved as a result of hot-pressing compared to conventional solid-state sintering. The value of the Li-ion lattice conductivity for dense tetragonal LLZO is 1.1×10−4 Scm−1. The microstructure of dense tetragonal LLZO consist of twins within the grains. It is suggested that the presence of twin boundaries adds a significant contribution to the total resistance. [Copyright &y& Elsevier]

On the path toward the design of Li-ion batteries with increased energy densities, efforts are focused on the development of positive electrodes that can maximize the voltage of the full cell. However, the development of novel materials that operate at high voltage, while also showing high efficiency and meeting strict safety standards, is an ongoing challenge. LiCoPO4 is being explored as a possible candidate, as the Co2+/3+ redox couple operates at 4.8 V versus Li+/Li0. The presence of phosphate groups is typically expected to stabilize the compound against oxygen loss, yet the changes in Co-O bonding upon Li extraction have not been ascertained. In addition, LiCoPO4 is riddled with problems relating to poor transport and strain in the crystal structure of the delithiated phase, which handicap its use as a high-voltage electrode. In this work, substituting ions to generate Li1.025Co0.84Fe0.10Cr0.05Si0.01(PO4)1.025 is found to stabilize both the electronic structure and crystal structure and, therefore, substantially improve the ability to fully utilize the redox capacity of the material. A thorough study by spectroscopic tools, combined with computations of the electronic structure, was used to probe changes in chemical bonding. The measurements revealed the existence of redox gradients between surface and bulk that are common in other materials that react at high potential. The study offers a comprehensive understanding of the fundamental reactions in LiCoPO4-type frameworks, while further demonstrating that ion substitution is an effective tool for improving their performance. [ABSTRACT FROM AUTHOR]

The elastic modulus, fracture toughness, ionic conductivity, Li and water stability of dense (~ 97%) fine-grain (~ 10 μm) Li 1.2 Zr 1.9 Sr 0.1 (PO 4 ) 3 (LZSP) consolidated by reactive hot-pressing was investigated. Low values of elastic modulus (25.2 and 40.9 GPa), fracture toughness (0.29 and 0.37 MPa-m 1/2 ), total conductivity (2.1 × 10 − 5 S/cm) at room temperature were exhibited as a result of the presence of microcracks formed during cooling from the hot-pressing temperature. The lattice conductivity of LZSP is 0.85 × 10 − 4 S/cm with an activation energy for bulk conductivity of 0.29 eV. The results of Li/LZSP/Li cell impedance as a function of time and surface examination suggest that LZSP is not stable against metallic lithium. The results of the water stability test suggest that LZSP is a possible membrane for use in aqueous Li-Air cells. The results of this study reveal for the case of lithium zirconium phosphates are as follows: 1] a small grain size is required to prevent microcracking to avoid a reduction in total conductivity and mechanical properties and 2] even though they do not contain a transition metal cation they are not stable against Li at room temperature. [ABSTRACT FROM AUTHOR]

Solid electrolytes based on the garnet crystal structure have recently been identified as a promising material to enable advance Li battery cell chemistries because of the unprecedented combination of high ionic conductivity and electrochemical stability against metallic Li. To better understand the mechanisms that give rise to high conductivity, the goal of this work is to correlate Li site occupancy with Li-ion transport. Toward this goal, the Li site occupancy is studied in cubic garnet as a function of Li concentration over the compositions range: Li7− xLa3Zr2− xTa xO12 ( x = 0.5, 0.75, and 1.5). The distribution of Li between the two interstitial sites (24d and 96h) is determined using neutron and synchrotron diffraction. The bulk conductivity is measured on >97% relative density polycrystalline specimens to correlate Li-ion transport as a function of Li site occupancy. It is determined that the conductivity changes nonlinearly with the occupancy of the octahedral (96h) Li site. It is shown that the effective carrier concentration is dependent on the Li site occupancy and suggests that this is a consequence of significant carrier-carrier coulombic interactions. Furthermore, the observation of maximum conductivity near Li = 6.5 mol is explained. [ABSTRACT FROM AUTHOR]

The effect of hot-pressing temperature on the microstructure and Li-ion transport of Al-doped, cubic Li7La3Zr2O12 ( LLZO) was investigated. At fixed pressure (62 MPa), the relative density was 86%, 97%, and 99% when hot-pressing at 900°C, 1000°C, and 1100°C, respectively. Electrochemical impedance spectroscopy showed that the percent grain-boundary resistance decreased with increasing hot-pressing temperature. Hot pressing at 1100°C resulted in a total conductivity of 0.37 mS/cm at room temperature where the grain boundaries contributed to 8% of the total resistance; one of the lowest grain-boundary resistances reported. We believe hot pressing is an appealing technique to minimize grain-boundary resistance and enable correlations between LLZO composition and bulk ionic conductivity. [ABSTRACT FROM AUTHOR]

Canine transmissible venereal tumor (CTVT) is the oldest known somatic cell lineage. It is a transmissible cancer that propagates naturally in dogs. We sequenced the genomes of two CTVT tumors and found that CTVT has acquired 1.9 million somatic substitution mutations and bears evidence of exposure to ultraviolet light. CTVT is remarkably stable and lacks subclonal heterogeneity despite thousands of rearrangements, copy-number changes, and retrotransposon insertions. More than 10,000 genes carry nonsynonymous variants, and 646 genes have been lost. CTVT first arose in a dog with low genomic heterozygosity that may have lived about 11,000 years ago. The cancer spawned by this individual dispersed across continents about 500 years ago. Our results provide a genetic identikit of an ancient dog and demonstrate the robustness of mammalian somatic cells to survive for millennia despite a massive mutation burden. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the perspective of lithium bis(oxalato)borate (LiBOB) as a possible candidate for the lithium ion batteries was evaluated on the basis of the knowledge accumulated thus far. Emphasis was placed on the electrochemistry of the BOB-anion on both graphitic anode and metal-oxide-based cathode surfaces. Certain issues associated with the impurity and safety of the salt in lithium ion systems were also discussed. [Copyright &y& Elsevier]

Among lithium-sulfur (Li-S) battery materials, sulfurized polyacrylonitrile (SPAN) has attracted substantial attention as a cathode material owing to its potential to bypass the problematic polysulfide formation and shuttling effect. Carbonate-based electrolytes have been eschewed compared with ether-based electrolytes because of their poor compatibility with Li metal anodes. In this work, we design and study an electrolyte comprising 0.8 M of lithium bis(trifluoromethanesulfonyl)imide, 0.2 M of lithium difluoro(oxalate)borate, and 0.05 M of lithium hexafluorophosphate in ethyl methyl carbonate/fluoroethylene carbonate = 3:1 v/v solution in the Li-S battery coupled with a Li metal anode and SPAN cathode. The well-designed carbonate-based electrolyte effectively stabilizes both electrodes, delivering high Coulombic efficiencies with stable cyclability. Studies using operando optical microscopy and atomic force microscopy demonstrate that dense, uniform Li deposition is promoted to suppress dendrite growth even at a high current density. Operando Raman spectroscopy reveals a reversible Li + storage behavior in the SPAN structure through the cleavage of disulfide bonds and their redimerization during lithiation and delithiation. As a result, the proposed Li-S battery delivers an overall capacity retention of 73.5% over 1000 cycles, with high Coulombic efficiencies over 99.9%.

Rechargeable Zn metal batteries (RZMBs) may provide a more sustainable and lower-cost alternative to established battery technologies in meeting energy storage applications of the future. However, the most promising electrolytes for RZMBs are generally aqueous and require high concentrations of salt(s) to bring efficiencies toward commercially viable levels and mitigate water-originated parasitic reactions including hydrogen evolution and corrosion. Electrolytes based on nonaqueous solvents are promising for avoiding these issues, but full cell performance demonstrations with solvents other than water have been very limited. To address these challenges, we investigated MeOH as an alternative electrolyte solvent. These MeOH-based electrolytes exhibited exceptional Zn reversibility over a wide temperature range, with a Coulombic efficiency > 99.5% at 50% Zn utilization without cell short-circuit behavior for > 1,800 h. More important, this remarkable performance translates well to Zn || metal-free organic cathode full cells, supporting < 6% capacity decay after > 800 cycles at -40 °C.

Evidence is presented that a "three-for-one" process based on two cross-relaxations between Pr 3+ ions efficiently populates the mid-infrared-emitting 3 H 5 manifold in a Pr 3+ -doped low-maximum-phonon-energy host. The concentration dependence of infrared fluorescence spectra and lifetimes of polycrystalline Pr:KPb 2 Cl 5 initially excited to the 3 F 3,4 manifolds indicate that the 3500-5500-nm fluorescence becomes strongly favored over shorter-wavelength infrared emission bands in the higher-concentration sample. The strong concentration dependence of the 3 F 3 and 3 H 6 manifold lifetimes suggests that both of these decay by cross-relaxation processes, resulting in more than one ion excited to 3 H 5 for each ion initially excited to 3 F 3 . Indeed, modeling and accounting for all possible decay paths indicate that, on average, about 2.3 ions are excited to 3 H 5 for each initially-excited ion. This confirms that the three-for-one excitation process must occur and contribute significantly to the total excitation efficiency. These results indicate that the two distinct cross-relaxation processes observed between Pr ions result in substantially higher excitation quantum efficiency, 230%, than any ever reported in rare-earth doped materials.