Inhibition of Si Fracture Via Rigid Solid Electrolyte Interphase in Lithium‐Ion Batteries

Abstract Numerous studies have demonstrated the importance of the solid electrolyte interphase (SEI) for Si‐adapted batteries. However, the development of a stable SEI that can withstand the volume change upon lithiation and delithiation of Si is challenging. Herein, the stability of an SEI on Si and its additional role in fracture inhibition are verified using electrochemical quartz crystal microbalance and scanning electron microscopy. A comparative study of various electrolytes confirms that the fluoroethylene carbonate‐derived SEI is not only stable, but also suppresses cracking in a thin‐film electrode. An underlying mechanism and the requirements for a fracture‐inhibiting SEI are proposed. To the best of the authors’ knowledge, this is the first time that it has been shown that an SEI can inhibit cracking in an active material, as well as suppress electrolyte decomposition. These results provide important insights into the insufficiently explored role of the SEI, which will guide the design of advanced battery systems using novel additives and coating materials.