Stress generation due to Li ion insertion into/extraction from LiMn2O4 particles is studied with a mathematical model for a lithium ion battery with pure LiMn2O4 or mixed LiMn2O4 and LiNi0.8Co0.15Al0.05O2 cathode. The simulated stress profile in a pure LiMn2O4 electrode shows nonuniformity across the positive electrode. The cathode blended model predicts that the stress generated in the LiMn2O4 particles is reduced at the end of discharge due to adding LiNi0.8Co0.15Al0.05O2 to the cathode. The effect of the variation in the blend ratio on the stress generation is also investigated.