Computer simulations are compared with experimental data for Bellcore PLION® cells using the graphite/1 M LiPF6 in EC:DMC (2:1)/LiMn2O4 system. The motivation is to model lithium-ion polymer cells having higher active material loadings and competitive energy densities and specific energies to liquid lithium-ion batteries. Cells with different electrode thickness, initial salt concentrations, and higher active material loadings were examined using the mathematical model to understand better the transport processes in the plasticized polymer electrolyte system. A better description of the ionic conductivity is employed based on new conductivity data. Improvements in the agreement between the simulations and experimental data are obtained by using the contact resistance at the current collector/electrode interface as an adjustable parameter for different cells, whose values vary from 20 to 35 Ω cm2 (based on separator area). The contact resistance is believed to originate at the mesh current collector interfaces. Reducing the salt diffusion coefficient by a factor of two or more at the higher discharge rates was necessary to obtain better agreement with the experimental data. Based on the experimental data and model predictions from this study, it can be concluded that the solution-phase diffusion limitations are the major limiting factor during high-rate discharges.