In Operando Monitoring the Stress Evolution of Silicon Anode Electrodes during Battery Operation via Optical Fiber Sensors

Abstract Silicon (Si) anode has attracted broad attention because of its high theoretical specific capacity and low working potential. However, the severe volumetric changes of Si particles during the lithiation process cause expansion and contraction of the electrodes, which induces a repeatedly repair of solid electrolyte interphase, resulting in an excessive consuming of electrolyte and rapid capacity decay. Clearly known the deformation and stress changing at µε resolution in the Si‐based electrode during battery operation provides invaluable information for the battery research and development. Here, an in operando approach is developed to monitor the stress evolution of Si anode electrodes via optical fiber Bragg grating (FBG) sensors. By implanting FBG sensor at specific locations in the pouch cells with different Si anodes, the stress evolution of Si electrodes has been systematically investigated, and Δσ/areal capacity is proposed for stress assessment. The results indicate that the differences in stress evolution are nested in the morphological changes of Si particles and the evolution characteristics of electrode structures. The proposed technique provides a brand‐new view for understanding the electrochemical mechanics of Si electrodes during battery operation.