A theoretical model of lithium-ion mass transport in a thin platelet-like active material particle of a composite electrode of a lithium-ion cell relative to the lithium-ion mass transport in the electrolyte was developed to provide insight into the performance behavior of the electrode. The developed formulation predicts the dimensionless transient lithium ion concentration profiles in the solid state active material particle, electrode-electrolyte interfacial current density, and g-moles of intercalatable lithium per g-mole of lithium-free electrode active material.