Electrochemical cycling-induced fatigue failure in all-solid-state composite structural supercapacitors under applied loads

In this study, a Zn-ion-based hybrid composite structural supercapacitor (CSS) incorporating a composite energy storage unit was developed. The electrochemical cycling-induced fatigue (electro-fatigue) failure and mechano-electrochemical coupling performance were investigated. In situ mechano-electrochemical characterizations reveal that the designed CSS exhibits a decreased capacity retention of 81.8% (49.3 ± 1.3 mAh g⁻¹) after 3000 cycles due to the structural failure even under low elastic stress preventing direct mechanical damage. The simulation results demonstrate that the Zn ion concentration gradient during charge-discharge process induces stress, progressively accumulating to fatigue stress over cycling. Furthermore, the coupling of electro-fatigue and applied low loads leads to a greater fatigue stress, which ultimately promotes structural degradation and electrochemical deterioration. These findings investigate the failure mechanism of CSSs caused by the cycling process, offering valuable insights and strategies for preserving both superior electrochemical and mechanical integrity.