Halogen Doping Mechanism and Interface Strengthening in the Na₃SbS₄ Electrolyte via Solid-State Synthesis

Good-performing sodium solid electrolytes (SSEs) areessentialfor constructing all-solid-state sodium-ion batteries operating atambient temperature. Sulfide solid electrolyte, Na3SbS4 (NBS), an excellent SSE with good chemical stability in humidair, can be synthesized with low-cost processing. However, Na3SbS4-based electrolytes with liquid-phase synthesisexhibit conductivities below milli-Siemens per centimeter. Thus, aseries of halogen-doped samples formulated as Na3-x SbS4-x M x (0 & LE; x & LE; 0.3, M =Cl, Br, and I) were experimentally prepared in this study using thesolid-state method to improve the battery performance. X-ray diffractionwith refinement analysis and Raman spectroscopy were employed to understanddeeply the connection between the crystal structure and conductivityof Na+ ions. In addition, symmetric sodium batteries withNa(2.85)SbS(3.85)Br(0.15) were tested atroom temperature, and pristine Na3SbS4 was usedas the control group. The result showed that the symmetric sodiumbattery assembled with the Na2.85SbS3.85Br0.15 electrolyte can stably cycle for longer than 100 h ata current density of 0.1 mA/cm(2). This research providesa method to manufacture novel SSEs by elaborating the effect of halogendoping in NBS.