Low-Temperature Sintering High-Density NASICON-Type Solid Electrolytes Boosting the Performance of Solid–Liquid Electrolyte Interphases

The NASICON-type Li1.3Al0.3Ti1.7(PO4)3 (LATP) has been extensively investigated owing to its excellent environmental stability, high ionic conductivity, and cost-effective raw materials. However, LATP solid electrolytes with low sinterability typically require sintering at temperatures exceeding 1000 °C. Additionally, the sluggish transport of Li+ at the solid–liquid interface limits the application of LATP-based solid–liquid hybrid lithium batteries. In this study, B-element doping was used in LATP to modify the P-content in the electrolyte material, which indirectly altered the proportion of the LiTiOPO4 secondary phase, leading to improved sinterability of the electrolyte. The resulting B-doped Li1.3Al0.23B0.07Ti1.7(PO4)3 (LABTP) was sintered at 750 °C through a conventional solid-phase sintering process. Notably, LABTP achieved a density of 98% and an ionic conductivity of 0.91 mS cm–1 at room temperature. Moreover, the high-density LABTP electrolyte pellet exhibited excellent interfacial compatibility with the liquid electrolyte, forming a long-term stable and robust solid–liquid electrolyte interphase with a significantly lower interfacial impedance of 20 Ω. The assembled lithium symmetric battery exhibited stable cycling for over 1500 h at a current density of 0.1 mA cm–2. This study presents a facile method for achieving low-temperature sintering of NASICON-type electrolytes, making them highly suitable for semisolid lithium metal batteries.