Hybrid amorphous-crystalline silicate composites as feasible solid-state electrolytes

Abstract

Solid-state electrolytes (SSEs) are considered as the most promising materials for enabling the safer, more efficient, and feasible solution to address the market demands for lithium-ion batteries. The current work investigates the production of inorganic SSEs from silicate minerals, which are abundant materials in natural resources (kaolinite) as well as in industrial waste-streams (amorphous silica). The synthesized materials showed high amorphous contents combined with lithium silicate phases at variable proportions, according to the molar proportions of the reacting system. The materials have been characterized with XRD, SEM/EDS, FTIR, TGA-DSC, XPS, EIS, and density measurements. The results showed that hybrid structures of amorphous and crystalline silicates can form an ordered hotchpotch morphology. The best of the hybrid SSEs presented ionic conductivity values of 1.42 × 10-4 and 1.30 × 10-4 Scm−1 for samples with total amorphous contents of 73 and 83 wt%, respectively. The connected structure between amorphous and crystalline phases in a hotchpotch structure is hypothesized to assist the hopping of the Li+ ions via combined mechanisms of segmental motion of the silicates amorphous chains with defects in the crystalline phases. The proposed approach may offer new research paths towards the low-cost scalable production of SSEs.

Keywords

• Lithium-ion batteries
• Solid-state electrolytes
• Lithium silicates
• Metakaolin
• Amorphous
• Crystalline