Modeling of the ratcheting behavior in flexible electrodes during cyclic deformation

Many flexible electrode materials with good electrochemical properties show poor sustainability due to the complex stress field inside the electrodes. Here, an analytical model is established to describe the ratcheting behaviors of the flexible electrode during electrochemical cycle with the presence of bending deformation, and is verified by finite element simulation. Under the impact of bending stress, the evolution of plastic strain during cyclic deformation is discussed and the effects of material softening due to the diffusion of Li-ions are considered. It is found that the electrode material accumulates a certain amount of plastic strain during each electrochemical cycle even under small bending deformation. Therefore, the flexible electrode material continuously accumulates plastic strain during cycling and becomes ineffective after several cycle times. Further, a strain hardening model is developed to discuss the possibility of mitigating ratcheting behavior. The increased yield strength in the cycling is found to be effective in suppressing the accumulation of plastic strain. The present work gives the new explanation for the poor sustainability of flexible batteries and provides a theoretical basis for further improvement.