Clarifying the Electro‐Chemo‐Mechanical Coupling in Li₁₀SnP₂S₁₂ based All‐Solid‐State Batteries

Abstract A fundamental clarification of the electro‐chemo‐mechanical coupling at the solid–solid electrode|electrolyte interface in all‐solid‐state batteries (ASSBs) is of crucial significance but has proven challenging. Herein, (synchrotron) X‐ray tomography, electrochemical impedance spectroscopy (EIS), time‐of‐flight secondary‐ion mass spectrometry (TOF‐SIMS), and finite element analysis (FEA) modeling are jointly used to decouple the electro‐chemo‐mechanical coupling in Li₁₀SnP₂S₁₂‐based ASSBs. Non‐destructive (synchrotron) X‐ray tomography results visually disclose unexpected mechanical deformation of the solid electrolyte and electrode as well as an unanticipated evolving behavior of the (electro)chemically generated interphase. The EIS and TOF‐SIMS probing results provide additional information that links the interphase/electrode properties to the overall battery performance. The modeling results complete the picture by providing the detailed distribution of the mechanical stress/strain and the potential/ionic flux within the electrolyte. Collectively, these results suggest that 1) the interfacial volume changes induced by the (electro)chemical reactions can trigger the mechanical deformation of the solid electrode and electrolyte; 2) the overall electrochemical process can accelerate the interfacial chemical reactions; 3) the reconfigured interfaces in turn influence the electric potential distribution as well as charge transportation within the SE. These fundamental discoveries that remain unreported until now significantly improve the understanding of the complicated electro‐chemo‐mechanical couplings in ASSBs.