Electrical Conductivity of Quartz Crystals

Enculescu, Ionuţ; Iliescu, B.

doi:10.1002/crat.2170320702

Cited by 6 publications

(7 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These calculations allow us to quantify the connection between the ability of the film to transport lithium ions and its performance. [22,[53][54][55] This model relates film thickness, Li solubility, and Li diffusivity with overpotential at a given current, providing a useful qualitative guideline for what coating properties are necessary to maintain acceptably low losses in the battery. As discussed in Section IIC, we model the ionic conductivity as if the coating were an Ohmic electrolyte with Li all in the form of Li + and a compensating background negative charge that is immobile.…”

Section: Electrolyte Model For Coatingsmentioning

confidence: 99%

“…From Eq. (2) the overpotential, V, across a coating film of thickness L when an electric current density J passes through it can be calculated as [22,[53][54][55]]…”

Section: Electrolyte Model For Coatingsmentioning

confidence: 99%

“…Verhoogen [54] first carried out a study of ionic diffusion and electric conductivity in natural -quartz crystals and also observed that diffusion was one-dimensional. Theories have been developed to understand ionic transport in these materials, [55] majorly focused on Al 3+ cations substituting for Si 4+ with commonly charge-compensated by interstitial monovalent cations such as Na + , Li + , and H + , or the holes that locate nearby the Al 3+ ions to form Al-Li, Al-Na, Al-OH, Al-hole centers. Obviously, Al 3+ defect plays a crucial role on the diffusion of Li + or Na + in these -quartz crystals, which is not the case in our problem above of the pure -quartz crystal without Al 3+ defect.…”

Section: -Siomentioning

confidence: 99%

“…However, we would like to stress here two relevant points: (i) It is generally accepted that ionic conductivity in quartz crystals is highly anisotropic (𝜎 // 𝜎 ⊥ ⁄ > 10 3 where 𝜎 // and 𝜎 ⊥ are the values of the conductivity in directions parallel and perpendicular to the c axis (the z-optical axis), respectively). [55] Monovalent alkali ions move freely in open channels along the c axis. This trend is consistent to our DFT calculation above showing the c axis preferential diffusion of Li + ions; (ii) It is also generally accepted that the ionic conductivity of quartz crystals is attributed to the migration of alkali metal ions thermally dissociated from Al-M (or [AlO 4 -M] 0 ) centers at temperature higher than 500 K, the dissociation reaction being [AlO 4 -M] 0 ⇌ [AlO 4 ] -+ [M] + .…”

Section: -Siomentioning

confidence: 99%

See 3 more Smart Citations

Lithium transport through lithium-ion battery cathode coatings

et al. 2015

View full text Add to dashboard Cite

The surface coating of cathodes using insulator films has proven to be a promising method for high-voltage 10 cathode stabilization in Li-ion batteries, but there is still substantial uncertainty about how these films function. More 11 specifically, there is limited knowledge of lithium solubility and transport through the films, which is important for coating 12 design and development. This study uses first-principles calculations based on Density Functional Theory to examine the 13 diffusivity of interstitial lithium in the crystals of α-AlF3, α-Al2O3, m-ZrO2, c-MgO, and α-quartz SiO2, which provide benchmark 14 cases for further understanding of insulator coatings in general. In addition, we propose an Ohmic electrolyte model to predict 15 resistivities and overpotential contributions under battery operating conditions. For the crystalline materials considered we 16 predict that Li + diffuses quite slowly, with a migration barrier larger than 0.9 eV in all crystalline materials except α-quartz SiO2, 17 which is predicted to have a migration barrier of 0.276 eV along <001>. These results suggest that the stable crystalline forms of 18 these insulator materials, except for oriented α-quartz SiO2, are not practical for conformal cathode coatings. Amorphous Al2O3 19 and AlF3 have higher Li + diffusivities than their crystalline counterparts. Our predicted amorphous Al2O3 resistivity (1789 MΩm) is 20 close to the top of the range of the fitted resistivities extracted from previous experiments on nominal Al2O3 coatings (7.8 to 913 21 MΩm) while our predicted amorphous AlF3 resistivity (114 MΩm) is very close to the middle of the range. These comparisons 22 support our framework for modeling and understanding the impact on overpotential of conformal coatings in terms of their 23 fundamental thermodynamic and kinetic properties, and support that these materials can provide practical conformal coatings 24 in their amorphous form.25 I. Introduction 26 27 Surface modification of the cathode by artificial coating is an effective strategy to stabilize Li-ion batteries (LIBs) 28 operating at high voltages.[1-10] Nevertheless, the coating functionalities and the stabilizing mechanisms are still not 29 fully understood and currently a subject of intensive research in the development of next-generation LIBs. Several 30 roles for the coating have been proposed to account for its positive impacts on the cathode performance, including: (i) 31 electrical conduction medium that facilitates electron transport between cathode active particles,[11] (ii) modifier of 32 cathode surface chemistry that changes chemical properties of the cathode surface to improve stability and 33 performance,[12] (iii) HF scavenger that locally reduces the acidity of the electrolyte near the cathode surface, thereby 34 reducing electrolyte degradation,[13-15] and (iv) physical protection barrier that suppresses electrolyte oxidation and 35 cathode corrosion. [8,[16][17][18][19][20] In general, role (iii) and, particularly, role (iv) are the most widely cl...

show abstract

Section: Electrolyte Model For Coatingsmentioning

confidence: 99%

“…From Eq. (2) the overpotential, V, across a coating film of thickness L when an electric current density J passes through it can be calculated as [22,[53][54][55]]…”

Section: Electrolyte Model For Coatingsmentioning

confidence: 99%

Section: -Siomentioning

confidence: 99%

Section: -Siomentioning

confidence: 99%

See 2 more Smart Citations

Lithium transport through lithium-ion battery cathode coatings

et al. 2015

View full text Add to dashboard Cite

show abstract

“…Other notable surface species that have been found in the surface of quartz following heat treatment are alkali ions, 26,27 in particular Na C ions. It may be noted that 2 ppm of bulk Na produces 2% of surface Na after 1000°C treatment and that such a level of contamination characterizes 'high purity' silica.…”

Section: Conduction Mechanisms For Silica Surfacesmentioning

confidence: 99%