The study aims to enhance the corrosion resistance of saggars used as sintering containers for lithium battery cathode materials. Under the typical sintering conditions, saggars undergo severe degradation due to lithium-ion corrosion, manifesting as surface spalling, slag formation, and structural fractures that ultimately lead to saggar failure. To mitigate these issues, we developed mullite-cordierite composite crucibles using an optimized formulation: coarse mullite particles (size from 1.18 to 0.6 mm) as the primary aggregate, combined with a matrix consisting of fine mullite (approximately 0.074 mm), cordierite (approximately 0.074 mm), calcined alumina (approximately 0.044 mm), Foshan yellow clay (approximately 0.044 mm), and coal gangue (approximately 0.044 mm). The effects of sintering temperature on phase evolution and microstructural development of saggar samples were systematically investigated, with parallel evaluation of their physical, mechanical, and corrosion-resistant properties. The optimal performance was achieved at a sintering temperature of 1380 °C for 3 hours, yielding saggars with a bulk density of 2.13 g·cm^-3 and a room temperature flexural strength of 10.26 MPa. These samples exhibited exceptional thermal shock resistance, maintaining 50% of their original strength after three thermal cycling tests. Additionally, increasing the content of coarse mullite particles (sizes from 1.18 to 0.6 mm) significantly improved the corrosion resistance of the saggars, as evidenced by the limited reaction layer thickness of merely 520 µm following 34 corrosion cycles.

Keywords: Mullite-cordierite, Refractoriness, Volumetric stability, Thermal shock resistance, Corrosion resistance.