Sodium ionic conductivity and stability of amorphous Na2O·2SiO2 added with MxOy (M=Zr, Y, and Sm)

Publication date: 5 April 2018
Source:Materials & Design, Volume 143
Author(s): Shan-Lin Zhang, Xiao-Na Wang, Cheng-Xin Li, Chang-Jiu Li
Amorphous Na2O·2SiO2 (A-Na2O·2SiO2) is one of the promising sodium ionic conductors for solid-state sodium-ion battery electrolytes owing to its easy preparation and low production cost. However, Na2O·2SiO2 glass suffers from relatively low conductivity and poor thermal stability as a result of crystallization and other defects. Herein, we improved the ionic conductivity and thermal stability of A-Na2O·2SiO2 by adding this material with metal oxides (MxOy, M=Y, Sm, and Zr) at varying loadings. The physical properties and stability of the A-Na2O·2SiO2 added with different oxides were systematically investigated. The results indicated that oxide adding on A-Na2O·2SiO2 resulted in larger density values that increased with the adding content. Additionally, oxide adding changed the strength of the SiO bond in A-Na2O·2SiO2, thereby affecting the overall network structure and uniformity. Among the different oxides prepared, added with 3mol% Sm2O3, 3mol% Y2O3, and 2mol% ZrO2 showed maximum hardness and elasticity modulus values. Additionally, oxide adding on A-Na2O·2SiO2 resulted in significantly improved ionic conductivity values. 3mol% Y2O3-added A-Na2O·2SiO2 material showed the highest ionic conductivity value (5.2×10⁻³Scm⁻¹) and optimum thermal stability, indicating that Y2O3-added Na2O·2SiO2 has high potential to be high-performance and stable sodium ionic conductors.

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