Essential structural and experimental descriptors for bulk and grain boundary conductivities of Li solid electrolytes

• Published in: Science and technology of advanced materials 2020-01, Vol.21 (1), p.712-725
• Main Authors: Wu, Yen-Ju, Tanaka, Takehiro, Komori, Tomoyuki, Fujii, Mikiya, Mizuno, Hiroshi, Itoh, Satoshi, Takada, Tadanobu, Fujita, Erina, Xu, Yibin
• Format: Article
• Language: English
• Subjects: 107 Glass and ceramic materials; 206 Energy conversion / transport / storage / recovery; 404 Materials informatics / Genomics; Algorithms; Bulk density; Conductivity; Conductors; descriptor; Electrolytes; Electronegativity; Energy Materials; Grain boundaries; grain boundary; Grain size; Ionic conductivity; ionic conductor; Ions; Li battery; Lithium; Machine learning; Molten salt electrolytes; Occupancy; Performance prediction; Resistance; Room temperature; Sintering; Solid electrolytes; Unit cell
• ISSN: 1468-6996; 1878-5514
• DOI: 10.1080/14686996.2020.1824985

We present a computational approach for identifying the important descriptors of the ionic conductivities of lithium solid electrolytes. Our approach discriminates the factors of both bulk and grain boundary conductivities, which have been rarely reported. The effects of the interrelated structural (e.g. grain size, phase), material (e.g. Li ratio), chemical (e.g. electronegativity, polarizability) and experimental (e.g. sintering temperature, synthesis method) properties on the bulk and grain boundary conductivities are investigated via machine learning. The data are trained using the bulk and grain boundary conductivities of Li solid conductors at room temperature. The important descriptors are elucidated by their feature importance and predictive performances, as determined by a nonlinear XGBoost algorithm: (i) the experimental descriptors of sintering conditions are significant for both bulk and grain boundary, (ii) the material descriptors of Li site occupancy and Li ratio are the prior descriptors for bulk, (iii) the density and unit cell volume are the prior structural descriptors while the polarizability and electronegativity are the prior chemical descriptors for grain boundary, (iv) the grain size provides physical insights such as the thermodynamic condition and should be considered for determining grain boundary conductance in solid polycrystalline ionic conductors.