Enhanced corrosion resistance and sintering mechanism of mullite-corundum saggar for cathode materials via a novel LiAlO2 coating strategy

Mullite-corundum saggars serve as essential containers for sintering lithium-ion cathode materials. However, these saggars are prone to reacting with cathode materials at elevated temperatures of 700-1100   o C, causing both structural degradation of saggars and the performance deterioration of cathode materials. Herein, the mullite-corundum saggar, which was coated with 6   wt% of LiAlO₂ and sintered at 1260 °C, exhibited optimal overall properties, including an apparent porosity of 17.56%, a cold modulus of rupture of 28.98   MPa, and a residual strength rate of 85.54%. Furthermore, the optimized mullite-corundum saggar with LiAlO 2 -based composite layer has significantly better corrosion resistance than the pristine one. During the sintering processes at 1260 °C, the formation of Li 2 O·Al 2 O 3 ·nSiO 2 phase enhances the bonding at the aggregate-matrix interface, which simultaneously suppresses the penetration and diffusion of Li 2 O, retards the reaction between the cathode material and the mullite-corundum saggar components, and finally improves corrosion resistance of the mullite-corundum saggar.