Many lithium-ion batteries have electrodes made of multiple types of active materials in order to take advantage of each active material. According to the types and blending ratios of constituting active materials, there can be numerous combinations of blended-electrodes, resulting in different performance characteristics. This paper introduces how to numerically model lithium-ion batteries with blended-electrodes, and predict their performance. Further, this paper demonstrates how to apply the developed model to designing new batteries. First, we propose an equilibrium model which can predict equilibrium characteristics of a blended-electrode. Second, a physics-based lithium-ion cell model with blended-electrodes is proposed. Developed model is validated with experimental data and shows good agreements.