Flexible Li-ion batteries (LIBs) have a strong oncoming consumer market demand for use in wearable electronic devices, flexible smart electronics, roll-up displays, electronic shelf labels, active radio-frequency identification tags, and implantable medical devices. This market demand necessitates research and development of flexible LIBs in order to fulfill the power requirements of these next-generation devices. In this study, the performance of semi solid anode for flexible Lithiumion battery was investigated through a mathematical model in order to reduce the number of experiments and to achieve the desired energy capacity of the battery. This model is a multiphysics three-dimensional heterogeneous model where all necessary transport phenomena including the charge and mass transfer and electrochemical reactions are considered at continuum mechanics level. COMSOL Multiphysics software is used to solve governing equations numerically using a finite element method. This model is for a half-cell simulation, and by using experimental results obtained in the lab. The maximum specific discharge capacity of the simulation Graphite/Li half-cell and LCO/Li reached up to 248(mAh/g) and 128(mAh/g), respectively, compared to the values received in the experimental test of ∼240 (mAh/g) for Graphite/Li and 120 (mAh/g) for LCO/Li. Overall, the simulation results were in acceptable agreement with those of the experiment. Parametric study was also performed to study the effect of adjustable parameters on the performance of both half cells. The difference in the discharge capacity was observed showing higher values at higher cell temperature and lower c-rate.