<p>The development of wearable electronics necessitates flexible and robust energy storage components to enhance comfort and battery longevity. The key to flexible batteries is improving electrochemical stability during deformation, which demands mechanical analysis for optimized design and manufacturing. This paper summarizes the progress of flexible batteries from a mechanical perspective, highlighting highly deformable structures such as fiber, wave, origami, and rigid-supple integrated designs. We discuss mechanical performance characterization and existing evaluation criteria for battery flexibility, along with simulation modeling and testing methods. Furthermore, we analyze mechano-electrochemical coupling, reviewing theoretical models that simulate mechanical and electrochemical behavior under various loads and introduce coupling tests that assess electrochemical performance during deformation. Finally, we suggest future research directions to advance flexible energy storage devices.</p>