Composite Electrolyte for All‐Solid‐State Lithium Batteries: Low‐Temperature Fabrication and Conductivity Enhancement

Abstract All‐solid‐state lithium batteries offer notable advantages over conventional Li–ion batteries with liquid electrolytes in terms of energy density, stability, and safety. To realize this technology, it is critical to develop highly reliable solid‐state inorganic electrolytes with high ionic conductivities and adequate processability. Li 1+ x Al x Ti 2− x (PO 4 ) 3 (LATP) with a NASICON (Na superionic conductor)‐like structure is regarded as a potential solid electrolyte, owing to its high “bulk” conductivity (ca. 10 −3 S cm −1 ) and excellent stability against air and moisture. However, the solid LATP electrolyte still suffers from a low “total” conductivity, mainly owing to the blocking effect of grain boundaries to Li + conduction. In this study, an LATP–Bi 2 O 3 composite solid electrolyte shows very high total conductivity (9.4×10 −4 S cm −1 ) at room temperature. Bi 2 O 3 acts as a microstructural modifier to effectively reduce the fabrication temperature of the electrolyte and to enhance its ionic conductivity. Bi 2 O 3 promotes the densification of the LATP electrolyte, thereby improving its structural integrity, and at the same time, it facilitates Li + conduction, leading to reduced grain‐boundary resistance. The feasibility of the LATP–Bi 2 O 3 composite electrolyte in all‐solid‐state Li batteries is also examined in this study.