Flexible batteries are becoming increasingly important due to the rapid growth of wearable electronics, soft robotics, and implantable biomedical devices, as they combine high energy density with mechanical flexibility. This study focuses on their design and performance under mechanical deformation, showing that bending creates a porosity gradient across the electrode thickness, with lower porosity on the compression side and higher porosity on the tension side. This non-uniform structure leads to uneven ionic conductivity and reduced electrochemical performance. A one-dimensional electrochemical model of a lithium-ion battery electrode was developed in COMSOL Multiphysics based on a porous electrode framework, where charge and mass transport in the solid and electrolyte phases were coupled with Butler–Volmer kinetics using Newman’s P2D model. Two electrode configurations were studied: a flat-state electrode with uniform porosity and a curved-state electrode with linearly graded porosity, with the porosity defined as a function of position while keeping a constant average solid volume fraction for fair comparison. Both modeling and experimental results indicate that bent cells exhibit lower discharge capacity compared to flat cells as the current rate increases from 0.1C to 2C.