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A New Model Linking Elastic Properties and Ion Conductivity in Mixed Network Former Glasses

Abstract

Glasses are promising candidate materials for all-solid state electrolytes for rechargeable batteries, due to their outstanding mechanical stability, wide electrochemical stability range, and open structure for potentially high conductivity. Mechanical stiffness and ionic conductivity are two key parameters for solid-state electrolytes. In this study, we investigate two mixed-network former glass systems, sodium borosilicate 0.2Na2O + 0.8[xBO1.5 + (1–x)SiO2] and sodium borogermanate 0.2Na2O + 0.8[xBO1.5 + (1–x)GeO2] glasses. With mixed-network formers, the structure of the network changes while the network modifier mole fraction is kept constant, i.e., x = 0.2, which allows us to analyze the effect of network structure on various properties, including ionic conductivity and elastic properties. Besides the non-linear, non-additive mixed glass former effect, we find that the longitudinal, shear and Young’s moduli depend on the combined number density of tetrahedrally and octahedrally coordinated network former elements. These units provide connectivity in three dimensions, which is required for the networks to exhibit restoring forces in response to isotropic and shear deformations. . Moreover, the activation energy for modifier cation, Na+, migration is strongly correlat-ed with the bulk modulus, suggesting that the elastic strain energy associated with the passageway dilation for the sodium ions is governed by the bulk modulus of the glass. The detailed analysis provided here gives an estimate for the number of atoms in the vicinity of the migrating cation that are affected by elastic defor-mation during the activated process. The larger this number and the more compliant the glass network, the lower is the activation energy for the cation jump.

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Publication details

The article was received on 06 Jul 2017, accepted on 05 Dec 2017 and first published on 05 Dec 2017


Article type: Paper
DOI: 10.1039/C7CP04534D
Citation: Phys. Chem. Chem. Phys., 2017, Accepted Manuscript
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    A New Model Linking Elastic Properties and Ion Conductivity in Mixed Network Former Glasses

    W. Wang, R. Christensen, B. Curtis, S. W. Martin and J. Kieffer, Phys. Chem. Chem. Phys., 2017, Accepted Manuscript , DOI: 10.1039/C7CP04534D

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