To extend the service life of cordierite-mullite saggar in the lithium-ion battery ternary cathode material (LiNixCoyMn1-x-yO2， LNCM) industry, silicon powder was introduced into cordierite-mullite samples and the effect of silicon powder content on the sintering performance, pore size distribution, mechanical properties, thermal shock stability, and corrosion resistance against LNCM was investigated. The results indicate that when the silicon powder content increases from 0% (mass fraction, the same below) to 5%, the liquid phase in the samples increases at high temperatures, promoting mass transport and the sintering process. The bonding between the aggregate and the matrix is enhanced, leading to a decrease in apparent porosity and pore size, while the strength and thermal shock resistance are improved. When the content of silicon powder increases to 7%, the interstices between the aggregate and the matrix are increased because of the significant shrinkage of the matrix, due to excessive liquid phase formation. Hence, the strength and the thermal shock resistance of samples are decreased. LiAlSiO4 and (Mg, Ni, Co, Mn)Al2O4 composite spinel are generated in the corrosion reaction between the LNCM and sample. The formation of LiAlSiO4 is accompanied by approximately 32% volumetric expansion, leading to cracking and spalling of samples. As the silicon powder content increases from 0% to 5%, the migration channel for LNCM is decreased due to the reduction in apparent porosity and pore size, significantly improving the corrosion resistance. When the content of silicon powder increases to 7%, the pore size of samples increases but the corrosion resistance is still improved slightly due to the formation of a continuous dense structure in the matrix. Overall, the sample with 5% silicon powder exhibits the best performance: the apparent porosity is 23.6%, with average pore sizes of 1.5 and 1.7 μm at the edge and center, respectively. The cold modulus of rapture and residual strength ratio after three times thermal shocks are 15.6 MPa and 86.1%, respectively, with an average corrosion layer thickness of 685 μm.