Aggregation between additive particles and active particles in battery electrode material strongly affects their interfacial phenomena and eventually battery performance. This paper proposes a three dimensional model to simulate the aggregation process of spherical carbon black (CB) and ellipsoidal LiMn2O4 active material (AM) particles within a liquid medium (PVDF polymer dissolved in NMP solvent) in the electrode materials of Li-ion batteries. Monte Carlo method is employed and the resulting aggregates are characterized by the number of CB particles connected to the percolated cluster of AM, which affects the effective conductivity. The effects of particle geometry and constituent mass ratio are investigated. It is found that a larger AM particle aspect ratio contributes positively to the percentage of CB attachment. For a given AM particle aspect ratio of 2 or 3, the average percentage of CB attachment is found to decrease as the CB:AM mass ratio increases from 2%:94% to 4%:92%. (C) 2014 The Electrochemical Society. All.rights reserved.