Intrinsic defects and conduction characteristics of Sc<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub></mml:math>O<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>3</mml:mn></mml:msub></mml:math>in thermionic cathode systems

Jacobs, Ryan; Booske, John H.; Morgan, Dane

doi:10.1103/physrevb.86.054106

Cited by 24 publications

(27 citation statements)

References 70 publications

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“…The values of ∆V obtained from different methods are within the same orders of magnitude (10 −2 eV) and the choice of ∆V does not change the magnitude of defect concentrations. In addition, a similar magnitude of ∆V has been observed in the literature 71 for other ionic materials.) A neutralization Jellium background charge was assumed by VASP to improve the energy convergence with respect to the supercell size.…”

supporting

confidence: 87%

“…The charged defects were modeled by adding (for negatively charged defects) or subtracting (for positively charged defects) one background electron to/from the total valence electrons in the supercell. In this study, the electrostatic energy correction (∆V ≈ 0.03 eV) was obtained from the average electrostatic energy difference between the defected cell (e.g., V − Li ) and the perfect cell 53,71,72 . (We noted that there are other methods to estimate ∆V , e.g., by inspecting the electrostatic potential far away from the charged defect 56 .…”

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confidence: 99%

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General method to predict voltage-dependent ionic conduction in a solid electrolyte coating on electrodes

2015

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Understanding the ionic conduction in solid electrolytes in contact with electrodes is vitally important to many applications, such as lithium ion batteries. The problem is complex because both the internal properties of the materials (e.g., electronic structure) and the characteristics of the externally contacting phases (e.g., voltage of the electrode) affect defect formation and transport. In this paper, we developed a method based on Density Functional Theory to study the physics of defects in a solid electrolyte in equilibrium with an external environment. This method was then applied to predict the ionic conduction in lithium fluoride (LiF), in contact with different electrodes which serve as reservoirs with adjustable Li chemical potential (µLi) for defect formation. LiF was chosen because it is a major component in the solid electrolyte interphase (SEI) formed on lithium ion battery electrodes. Seventeen possible native defects with their relevant charge states in LiF were investigated to determine the dominant defect types on various electrodes. The diffusion barrier of dominant defects was calculated by the Climbed Nudged Elastic Band Method. The ionic conductivity was then obtained from the concentration and mobility of defects using the Nernst-Einstein relationship. Three regions for defect formation were identified as a function of µLi: 1) intrinsic, 2) transitional, and 3) p-type region. In the intrinsic region (high µLi, typical for LiF on the negative electrode), the main defects are Schottky pairs and in the p-type region (low µLi, typical for LiF on the positive electrode) are Li ion vacancies. The ionic conductivity is calculated to be approximately 10 −31 Scm −1 when LiF is in contact with a negative electrode but it can increase to 10Scm −1 on a positive electrode. This new insight suggests that divalent cation (e.g., Mg 2+ ) doping is necessary to improve Li ion transport through the engineered LiF coating, especially for LiF on negative electrodes. Our results provide a new understanding of the influence of the environment on defect formation and demonstrate a linkage between defect concentration in a solid electrolyte and the voltage of the electrode.

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confidence: 87%

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confidence: 99%

General method to predict voltage-dependent ionic conduction in a solid electrolyte coating on electrodes

2015

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“…The positions of strontium atoms and defects in La 1.85 Sr 0.15 CuO 4 were taken from Xie et al 29 , who used the special quasirandom structure method to determine the placement of strontium dopants 38 . For the two types of O interstitial defects, the defects were inserted into the rock salt plane, and the oxide interstitial was positioned at approximate reduced cell coordinates of (0.15, 0.13, 0.25) (≈2.3 Å away from the nearest apical O) and the peroxide interstitial was positioned at approximate reduced cell coordinates of (0.18, 0.18, 0.21) (≈ 1.5 Å away from the nearest apical O), consistent with the work of Xie et al 29 Defect formation energy calculations were performed using standard defect thermodynamics models, as detailed elsewhere 29, 39 . In the cases where defects were calculated with lattice strain, the strain was imposed on the a -axis and b -axis lattice parameters, and the c -axis was allowed to fully relax.…”

Section: Methodsmentioning

confidence: 84%

Strain control of oxygen kinetics in the Ruddlesden-Popper oxide La1.85Sr0.15CuO4

et al. 2018

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Oxygen defect control has long been considered an important route to functionalizing complex oxide films. However, the nature of oxygen defects in thin films is often not investigated beyond basic redox chemistry. One of the model examples for oxygen-defect studies is the layered Ruddlesden–Popper phase La2−xSrxCuO4−δ (LSCO), in which the superconducting transition temperature is highly sensitive to epitaxial strain. However, previous observations of strain-superconductivity coupling in LSCO thin films were mainly understood in terms of elastic contributions to mechanical buckling, with minimal consideration of kinetic or thermodynamic factors. Here, we report that the oxygen nonstoichiometry commonly reported for strained cuprates is mediated by the strain-modified surface exchange kinetics, rather than reduced thermodynamic oxygen formation energies. Remarkably, tensile-strained LSCO shows nearly an order of magnitude faster oxygen exchange rate than a compressively strained film, providing a strategy for developing high-performance energy materials.

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“…For instance, Jacobs et al 64 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 larger than those of the GGA calculations by about 2 eV, but still lower than the experimental measurements by about 3 eV, for both materials. In addition, we evaluated the formation energies for two defect systems: a positively charged fluorine vacancy and neutral Schottky defect where lithium and fluorine vacancies are nearest neighbors.…”

Section: Iii2 Defect Thermodynamics In Lif and Nafmentioning

confidence: 99%

First-Principles Analysis of Defect Thermodynamics and Ion Transport in Inorganic SEI Compounds: LiF and NaF

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Chan

et al. 2015

ACS Appl. Mater. Interfaces

221

162

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The formation mechanism and composition of the solid electrolyte interphase (SEI) in lithium ion batteries has been widely explored. However, relatively little is known about the function of the SEI as a transport medium. Such critical information is directly relevant to battery rate performance, power loss, and capacity fading. To partially bridge this gap in the case of inorganic SEI compounds, we report herein the results of first-principles calculations on the defect thermodynamics, the dominant diffusion carriers, and the diffusion pathways associated with crystalline LiF and NaF, which are stable components of the SEI in Li-ion and Na-ion batteries, respectively. The thermodynamics of common point defects are computed, and the dominant diffusion carriers are determined over a voltage range of 0-4 V, corresponding to conditions relevant to both anode and cathode SEI's. Our analyses reveal that for both compounds, vacancy defects are energetically more favorable, therefore form more readily than interstitials, due to the close-packed nature of the crystal structures. However, the vacancy concentrations are very small for the diffusion processes facilitated by defects. Ionic conductivities are calculated as a function of voltage, considering the diffusion carrier concentration and the diffusion barriers as determined by nudged elastic band calculations. These conductivities are more than ten orders of magnitude smaller in NaF than in LiF. As compared to the diffusivity of Li in other common inorganic SEI compounds, such as Li2CO3 and Li2O, the cation diffusivity in LiF and NaF is quite low, with at least three orders of magnitude lower ionic conductivities. The results quantify the extent to which fluorides pose rate limitations in Li and Na batteries.

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Intrinsic defects and conduction characteristics of Sc2O3in thermionic cathode systems

Cited by 24 publications

References 70 publications

General method to predict voltage-dependent ionic conduction in a solid electrolyte coating on electrodes

General method to predict voltage-dependent ionic conduction in a solid electrolyte coating on electrodes

Strain control of oxygen kinetics in the Ruddlesden-Popper oxide La1.85Sr0.15CuO4

First-Principles Analysis of Defect Thermodynamics and Ion Transport in Inorganic SEI Compounds: LiF and NaF

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