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Du, Yaojun A.; Holzwarth, N. A. W.

doi:10.1103/physrevb.76.174302

Cited by 99 publications

(56 citation statements)

References 42 publications

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“…Recently, solid electrolytes attracted a lot of research emphasizes not only because of the promising future of all-solid batteries 4,[8][9][10][11][12][13][14][15][16] , but also their importance as an interfacial layer between electrodes and liquid electrolytes, known as a solid electrolyte interphase (SEI) 17,18 . The performance of liquid electrolyte based LIBs relies on forming a stable SEI on the electrode surface.…”

Section: 5mentioning

confidence: 99%

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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Section: 5mentioning

confidence: 99%

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

2015

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“…Typically, it has been reported Du and Holzwarth (2007) that results obtained using the LDA exchange-correlation functional (Perdew and Wang (1992)) tend to underestimate the lattice parameters by 2% while results obtained using the GGA exchange-correlation functional (Perdew et al (1996)) tend to overestimate the lattice parameters by 1%. On the other hand, for most materials, the fractional coordinates computed for the non-trivial site positions are nearly identical (within 0.1%) for LDA and GGA calculations in comparison with experiment.…”

Section: Calculational Methodsmentioning

confidence: 97%

First Principles Modeling of Electrolyte Materials in All-Solid-State Batteries

Holzwarth

2014

Physics Procedia

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“…24,27,28 Among a wide range of Li x PO y N z (x = 2y + 3z -5) compositions that exhibited acceptable ionic conductivity, 8,14,29,30 we intended to model the one with the highest ionic conductivity. Several experimental demonstrations of the increased ionic conductivity with the N/P ratio 31-33 motivated us to choose the stoichiometry of Li 4 PO 3 N, which has a high (and experimentally confirmed 32 ) N/P ratio.…”

Section: Computational Modeling and Methodologymentioning

confidence: 99%

“…[24][25][26] Instead, we aimed to model a representative single crystal structure that could be the most dominant part of the amorphous LiPON structure, which will be identified by the probability of distribution based on the thermodynamic energy of each candidate crystal. 24,27,28 Among a wide range of Li x PO y N z (x = 2y + 3z -5) compositions that exhibited acceptable ionic conductivity, 8,14,29,30 we intended to model the one with the highest ionic conductivity. Several experimental demonstrations of the increased ionic conductivity with the N/P ratio [31][32][33] motivated us to choose the stoichiometry of Li 4 PO 3 N, which has a high (and experimentally confirmed 32 ) N/P ratio.…”

Section: Computational Modeling and Methodologymentioning

confidence: 99%

Effects of Mechanical Strain on Ionic Conductivity in the Interface between LiPON and Ni-Mn Spinel

Thai

Lee

2017

J. Electrochem. Soc.

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We present first-principles calculations to understand ionic conductivity in the interface between lithium phosphorous oxynitride (LiPON) and Ni-Mn spinel (LNM), with emphasis on the effect of mechanical strain. Two LiPON/LNM interfaces, one with and the other without BaTiO 3 (BTO) additive, are modeled as abrupt interfaces to minimize the effects of the space-charge layer formation. It is observed that the interface with BTO additive has higher ionic conductivity than the other. Comparison of structural geometry indicates that the LiPON part of the LiPON/LNM interface is contracted but it recovers with BTO additive, which suggests the relevance of mechanical strain to ionic conductivity in these interfaces and the role of BTO in controlling the mechanical strain. The activation energy barriers of Li-hopping in a bulk LiPON, calculated at different levels of mechanical strain, exhibit a significant increase with compressive strain, supporting the suggested effect of mechanical strain in the interfaces. This result implies that ionic conductivity in the interface between LiPON and cathode can be enhanced by modifying the interface but with appropriate size and distribution of additives. The combination of a metal-oxide cathode and organic liquid electrolytes has become a leading type of Li-ion batteries (LIB) for years.1-3 However, the use of liquid electrolytes constrains the electrochemical performance and lifetime of LIB due to multiples issues, in particular regarding safety. [4][5][6][7] One strategy to rectify these issues is to employ solid electrolytes instead, aiming at all solid-state LIB (ASSLIB). As solid electrolytes are not prone to the same flammability hazards as liquid electrolyte batteries are, ASSLIB can offer favorable cycling, longer shelf life, increased packing efficiency, and the use of higher voltage cathodes leading to higher energy density.3,8-13 Furthermore, solid-state electrolytes have flexible composition, absence of grain boundaries, and a hard surface, which can lead to suppressing side reactions and inhibiting dendritic growth of lithium. 3,8,[14][15][16] As a key component of ASSLIB, solid-state electrolytes should permit high mobility of Li-ions between anode and cathode while blocking conduction of electrons. Lithium phosphorous oxynitride (LiPON) has attracted attention as a promising candidate to satisfy these conditions. 8,14,16,17 As an amorphous material, LiPON has exhibited an acceptable ionic conductivity (∼10 −6 S/cm) compared to crystalline structures 18,19 and negligible electronic conductivity measured around < 10 −14 S/cm. 16,18 In addition, LiPON can be fabricated as a film structure with excellent electrochemical stability up to 5.5 V 3,8,15 and have also been shown to exhibit high cyclability. 8,20 Despite all these advantages, the commercialization of LiPON has been delayed due to relatively slow ionic conduction in the LiPONemployed ASSLIB compared to that of the LIB utilizing liquid electrolytes. Large interfacial resistance has been alleged to be a major fac...

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Mechanisms ofLi+diffusion in crystallineγ- andβ−Li3

Cited by 99 publications

References 42 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

First Principles Modeling of Electrolyte Materials in All-Solid-State Batteries

Effects of Mechanical Strain on Ionic Conductivity in the Interface between LiPON and Ni-Mn Spinel

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