Synthesis and Sintering of Li_1.3Al_0.3Ti_1.7(PO₄)₃@Li₂O–2B₂O₃ Core–Shell Solid Electrolyte Powders Prepared via One-Pot Spray Pyrolysis

Developing a rational design for oxide-based solid electrolytes to promote ionic conductivity, decrease the sintering temperature, and improve stability with metallic Li is challenging. Herein, core–shell-structured Li_1.3Al_0.3Ti_1.7(PO₄)₃@Li₂O–2B₂O₃ (LATP–LBO) microspheres are prepared using one-pot spray pyrolysis. Phase separation between crystalline LATP and amorphous LBO leads to the formation of a core–shell-structured LATP–LBO composite. On the surface of LATP–LBO composite, the LBO shell forms a liquid phase during low-temperature sintering, thereby enhancing the densification. The LBO shell also decreases the grain boundary resistance by forming a thin layer between the LATP grains, thus increasing the total ionic conductivity. Because Li-ion conductive LBO occupies the grain boundary, a total ionic conductivity of 1.519 × 10⁻⁴ S cm⁻¹ is achieved at a low sintering temperature of 700 °C. Additionally, the LBO shell provides good electrochemical stability for LATP with metallic Li. The improved ionic conductivity and chemical stability can be attributed to the synergistic advantages of the spherical morphology, core–shell structure, and uniformity of LBO.