High-Pressure, Low-Temperature Synthesis of Li _{1+ x} Al _x Ti _{2– x} (PO ₄ ) ₃ Solid Electrolytes for High-Performance Solid-State Batteries

Conventional high-temperature sintering of oxide solid electrolytes often induces lithium loss, impurity formation, and microstructural defects, which severely compromise the ionic conductivity. To overcome these limitations, a high-pressure, low-temperature (HP-LT) sintering strategy is developed. This process produces a highly dense (94.2%) NASICON-type Li 1+ x Al x Ti 2– x (PO 4 ) 3 (LATP) ceramic at low temperatures, exhibiting a remarkable room-temperature ionic conductivity of 9.46 × 10 –4 S/cm, 4 times that of conventionally sintered counterparts. Comprehensive characterizations, including XRD, SEM, density, and electrochemical impedance measurements, reveal that the enhanced performance originates from the effective suppression of material decomposition and the significant promotion of interfacial ionic transport enabled by the HP-LT approach. This work demonstrates HP-LT synthesis as an efficient and scalable route for fabricating high-performance LATP electrolytes, paving the way toward advanced all-solid-state batteries.