| Pushing the Limit of in-Situ Characterization in All-Solid-State Battery: Full Decomposition Mechanism of Na3SbS4 Electrolyte Under Precise Potential ControlWith its higher ionic conductivity and lower flammability, the all-solid-state battery (ASSB) is expected to become a promising alternative to current liquid-state batteries. As the key difference between those two types of cells, electrolyte presenting in solid phase introduces additional complexity such as the formation of a solid electrolyte interface (SEI) in an imperfect solid-solid interface. Compared with liquid batteries, this imperfect contact in ASSBs leads to a heterogeneous decomposition and a more complicated SEI formation mechanism. Moreover, the opaque nature in ASSBs also challenges the conventional optical spectroscopy method used to characterize their decay mechanism. Therefore, a post-cycle ex-situ characterization remains the most widely applied approach to study the decomposition in ASSB [1]. However, as the key trigger of SEI formation, the stepwise involvement of anodic or cathodic potentials in electrolyte decomposition is not well understood. Despite significant challenge in characterization method design, in-situ study remains a pivotal approach to a complete kinetic and thermodynamic story of decomposition mechanism in the ASSB.
In our previous work, in-situ Raman characterization was performed at the anode/electrolyte interface in sodium ASSB [2]. This non-destructive method with an easy set-up has shown its potential in the study of SEI formation mechanisms, but the precise control of the potential experienced by electrolyte failed due to the heterogeneity of the electrode/electrolyte contact. In this study, we optimize our previous old Raman experiment set-up and achieve precise characterization of the electrochemical window (EW) of Na3SbS4 (NAS) and its derivative, carboxymethyl cellulose coated NAS (NAS-CMC). Precise potential control was accomplished by a hybridizing electrolyte design. Our results have suggested that NAS exhibit an EW from + 1.34 V to + 2.10 V vs Na/Na+. NAS was reduced to Na-Sb binary below 1.34 V, and this process was partially reversible. Additionally, another decomposition mechanism causes NAS to irreversibly decompose into Na3SbS3, but this mechanism doesn’t have a clear critical potential. At potentials more positive than 2.10 V, NAS was oxidized to form an Sb-S complex. In contrast, NAS-CMC shows suppressed decomposition to Na-Sb binary, and the critical potential of this decomposition is lowered to 1.0 V~ 0.4 V. Up to now, many following-up experiments are being performed and more details will be shared during the meeting.
References:
1. Jia, H. H.; Peng, L. F.; Yu, C.; Dong, L.; Cheng, S. J.; Xie, J. Mater.Chem. A 2021, 9 (9), 5134−5148.
2. Xie, G.; Tang, M.; Xu, S. H.; Brown, A.; Sang, L. ACS Appl. Mater. Interfaces 2022, 14, 43, 48705–48714 University of Alberta | Activity | 2025-05-18 | Xie, G., Sang, L. |
