The effect of nano-scale particle size on the performance of Li4Ti5O12 (LTO) electrode is investigated by computational simulation. Newman pseudo-2D (P2D) model is utilized to characterize the performance of LTO electrode. However, unlike previous P2D lithium ion battery (LIB) models, the model design adjustable parameters are set based on the experimental data obtained from monodispersed active electrode particles. This allows the model to accurately reflect real battery performance. The model provides the optimum nano-particle size for a specific application, which eliminates the performance loss due to the limited mass transportation. The model can be employed for a wide range of electrode materials to optimize the particle-size and reduce fabrication costs by avoiding unnecessary particle size reduction.