Clean Synthesis of Oxide Electrolytes via a Boiling Water-Assisted Solid-Phase Sintering Route

Solid-phase sintering (SS) is a widely used method for synthesizing oxides due to its simplicity and scalability. However, it typically relies on organic liquids as grinding media, resulting in higher costs and environmental pollution. This study proposes a boiling water-assisted solid-phase sintering (BWA-SS) method for synthesizing oxide electrolyte materials, in which water is used as the grinding medium and the precursor slurry is directly sintered, providing an eco-friendly process. More importantly, finite element analysis shows that this method prevents the uneven sedimentation of raw material particles by secondary dispersion caused by the vapor mass flux gradient in boiling water. Using this organic-free method, the pure Li7La3Zr2O12 (LLZO) solid electrolyte is successfully synthesized, achieving a high ionic conductivity (σi) of 6.22 × 10-4 S/cm, which is comparable to that of LLZO solid electrolyte material produced by the conventional SS method. The assembled Li/LLZO/Li symmetrical cell exhibits stable cycling for 3000 h at a current density of 0.1 mA/cm2. This method has also been successfully extended to the synthesis of other solid electrolytes (LiTa2PO8, LTPO) and cathode materials (LiNi0.8Co0.1Mn0.1O2, NCM811), demonstrating potential for clean preparation of various oxide materials.