Crystallizable Ti- and Ge-based glasses as an active sintering aid for LATP ceramics: Low-temperature densification and enhanced ionic conductivity

Li1.3Al0.3Ti1.7(PO4)3 (LATP) is a promising oxide solid electrolyte for all-solid-state lithium-ion batteries, but high-temperature sintering and large grain-boundary resistance limit its practical application. In this study, Li–Al–Ti–P–O and Li–Al–Ge–P–O glasses were investigated as crystallizable sintering additives for LATP solid electrolytes and compared with conventional Li3PO4. The Ti-based glass promoted low-temperature densification, achieving a relative density of 95.1 % and a total ionic conductivity of 1.60 × 10−4 S cm−1 after pressureless sintering at 800 °C for 2 h. The Ge-based glass showed a higher conductivity of 2.88 × 10−4 S cm−1 at 900 °C, exceeding those of Li3PO4 and the Ti-based glass under the same condition. Impedance analysis indicated that this enhancement was mainly due to reduced grain-boundary resistance. Raman spectroscopy suggested that the Ge-based glass suppressed the formation of resistive Ti-related impurity phases observed in the Li3PO4- and Ti-based-glass-added samples. These results demonstrate that crystallizable Ti- and Ge-based glass additives can function as active sintering aids for LATP, with the Ti-based glass enhancing low-temperature densification and the Ge-based glass improving grain-boundary Li-ion transport.