Multiscale mechano-electrochemical degradation mechanisms of gel electrolytes for flexible solid-state batteries

Flexible solid-state batteries are inevitably subjected to complex dynamic mechanical loads in service. The core gel electrolyte is highly sensitive to mechanical stress, resulting in fatigue effect triggered by cyclic load, which directly threatens the mechanical integrity and electrochemical reliability of batteries. Herein, the quantitative analysis of macro-microstructure evolution and dynamic response of gel electrolyte under bending fatigue load is realized by using digital image correlation (DIC) technology and scanning electron microscope (SEM). The results indicate that the prepared gel electrolyte has good mechanical and electrochemical properties, showing strong cyclic dependence and angular correlation. As the bending cycle number and bending angle increase, the electrolyte surface undergoes periodic buckling deformation, accompanied by increased heterogeneity of strain filed. Moreover, the fatigue resistance of the electrolyte is significantly negatively correlated with the bending angle. For multiple cyclic loads and large bending angles, the electrolyte undergoes stress concentration, which leads to defect nucleation and crack propagation, and ultimately attenuates the electrochemical performance. This study reveals the mechano-electrochemical coupling mechanism of gel electrolyte, and provides guidance for the optimization of electrolyte anti-fatigue performance and the structural design of flexible solid-state batteries.