In the past two decades, various research works have been conducted in the field of flexible electronic devices (FEDs). Researchers have focused their efforts on solving the existing challenges in the electronic, electrochemical, and mechanical behaviors of FEDs. The importance of flexible lithium-ion batteries (FLIBs) in the area of FEDs is evident; however, less attention has been paid to the mechanical behavior of FLIBs in comparison with the material and electrochemical characteristics. The present paper reviewed the research works in the FLIBs, focusing on their mechanical integrity and electrochemical performances. First, an introduction to FLIBs was presented, and the previous review papers published in this field were briefly introduced. Then, a detailed review of the available electrochemical and mechanical research works on FLIBs was presented. Moreover, the mechanical testing methods (tensile, compressive, indentation, fatigue, and adhesion) for the characterization of FLIBs’ components, the research works on the simulation and modeling of the mechanical behavior of FLIBs, and a summary of the present situation and the future trend of research in this field were reviewed and presented.