Li Ion Diffusion Mechanisms in the Crystalline Electrolyte γ-Li[sub 3]PO[sub 4]

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

doi:10.1149/1.2772200

Cited by 72 publications

(80 citation statements)

References 26 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%

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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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Section: 5mentioning

confidence: 99%

“…As a result, the defect formation can be approximated by the reaction (15) and the defect concentration can be estimated by • p-type Region: the defect formation is dominated by reaction (16) • Transitional Region: defects are formed by both reactions (15) and (16). In this region, the concentrations of V Figure 3.…”

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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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“…Interestingly, the path dependence of energy barrier is also observed in other computational studies on the γ-Li 3 PO 4 -based LiPON models. 36,38,56 For example, Du and Holtzwarth reported 0.2∼0.9 eV of the energy barriers for interstitial Li ion migration in the γ-Li 3 PO 4 depending on the local concentration of PO 3 N defects around the migrating Li ion. 56 It is observed that the average energy barrier of each type increases with compressive strain, while it fluctuates or even gradually decreases with tensional strain.…”

Section: Resultsmentioning

confidence: 99%

“…), to achieve Li 4 PO 3 N. Among two common crystal structures of Li 3 PO 4 , labeled β and γ, 34,35 β-Li 3 PO 4 was selected as it is more thermodynamically stable than γ-Li 3 PO 4 . 29,36,37 There are four void spaces, enclosed by six cations (Li or P) and six anions (O), per f.u., as illustrated Figure 1a. It was reported that the Li diffusion in γ-Li 3 PO 4 was dominated via an interstitial mechanism, 30,38 which implies these void spaces would be treated as interstitial sites, considering the only major difference between β-and γ-Li 3 PO 4 is the relative orientation of PO 3− 4 .…”

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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“…Holzwarth et al [117][118][119][120][121][122] explored Li + diffusion in the Li 3 PO 4 and thio-phosphate materials with NEB methods. A general conclusion is that the migration barriers of Li + in thio-phosphates are much lower than those in phosphates with similar structures (Figure 10), in line with the general intuition that the larger and more polarizable S 2-anion promotes higher Li + mobility.…”

Section: Phosphates and Thio-phosphatesmentioning

confidence: 99%

Computational studies of solid-state alkali conduction in rechargeable alkali-ion batteries

Deng

Ong

2016

NPG Asia Mater

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The facile conduction of alkali ions in a crystal host is of crucial importance in rechargeable alkali-ion batteries, the dominant form of energy storage today. In this review, we provide a comprehensive survey of computational approaches to study solid-state alkali diffusion. We demonstrate how these methods have provided useful insights into the design of materials that form the main components of a rechargeable alkali-ion battery, namely the electrodes, superionic conductor solid electrolytes and interfaces. We will also provide a perspective on future challenges and directions. The scope of this review includes the monovalent lithium-and sodium-ion chemistries that are currently of the most commercial interest. NPG Asia Materials (2016) 8, e254; doi:10.1038/am.2016.7; published online 25 March 2016 INTRODUCTIONThe facile conduction of alkali ions in a crystal is of critical importance in energy storage. Today, the dominant form of energy storage in consumer electronics is the rechargeable lithium-ion (Li-ion) battery, 1-5 a device that functions entirely on the basis of the reversible transport of Li + ions. With one of the highest energy densities of known energy storage technologies, Li-ion batteries are finding increasingly large-scale applications in electrified transportation and grid storage. In recent years, there has also been a resurgence of interest in rechargeable sodium-ion (Na-ion) batteries, 6-12 which function on the same basic principle but with Na + instead of Li + because of concerns regarding the abundance and cost of lithium. Figure 1 shows a representation of a rechargeable alkali-ion battery. The typical electrode in an alkali-ion battery is an intercalation compound, which, as the name implies, stores alkali ions by inserting them into its crystal structure in a topotactic manner. During discharge, A + ions are transported from the anode, through the electrolyte and into the cathode. The reverse happens during charge. Throughout this review, we will adopt the customary terminology of defining the 'cathode' as the positive electrode during discharge, even though the formal definition of the cathode changes depending on whether the charging or discharging process is being referred to. Current cathodes are typically transition metal oxides, and the insertion/removal of each A + in the cathode is accompanied by the concomitant reduction/oxidation of a transition metal ion to accommodate the compensating insertion/removal of an electron. Graphitic carbon is the most common anode.The performance of a rechargeable alkali-ion battery depends crucially on the ease with which alkali ions move in the host crystal of the cathode and anode, in the electrolyte, and in the electrodeelectrolyte interface. Poor alkali transport in any part of the battery

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Li Ion Diffusion Mechanisms in the Crystalline Electrolyte γ-Li[sub 3]PO[sub 4]

Cited by 72 publications

References 26 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

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

Computational studies of solid-state alkali conduction in rechargeable alkali-ion batteries

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