Use of Coal Gangue to Prepare Refractory Saggars with Superior Corrosion Resistance and Thermomechanical Properties for the Calcination of Li-Ion Battery Cathode Materials

Mullite (3Al2O3·2SiO2) is commonly used as the basic component to prepare refractory saggars for the calcination of Li-ion battery (LIB) cathode materials. Coal gangue, basically treated as aluminosilicate solid waste/tailings, could be used as the starting material to synthesize mullite at elevated temperatures. However, high operation energy and additional high-quality alumina sources are required in this process. In addition, mullite is prone to corrosion by LIB cathode materials, which remains a major challenge. The present work reports the design and fabrication of refractory powders with a core–shell structure comprising calcined coal gangue (CCG) and a layer of in situ-generated KAlSi2O6 (KAS4) around CCG grains. The obtained CCG–KAS4 powders with a core–shell structure exhibit superior corrosion resistance against the Li(NixCoyMnz)O2 precursor/material during calcination compared with CCG or mullite. Materials prepared with CCG–KAS4 powders containing 4.2 and 8.4 wt % KAS4 possess better thermomechanical properties than those synthesized from mullite powders. This makes coal gangue a good candidate to prepare refractory saggars for the calcination of LIB cathode materials.