Low‐Cost Preparation of High‐Performance Na‐B‐H‐S Electrolyte for All‐Solid‐State Sodium‐Ion Batteries

All‐solid‐state sodium‐ion batteries have the potential to improve safety and mitigate the cost bottlenecks of the current lithium‐ion battery system if a high‐performance electrolyte with cost advantages can be easily synthesized. In this study, a one‐step dehydrogenation‐assisted strategy to synthesize the novel thio‐borohydride (Na‐B‐H‐S) electrolyte is proposed, in which both raw material cost and preparation temperature are significantly reduced. By using sodium borohydride (NaBH(4)) instead of B as a starting material, B atoms can be readily released from NaBH(4) with much less energy and thus became more available to generate thio‐borohydride. The synthesized Na‐B‐H‐S (NaBH(4)/Na‐B‐S) electrolyte exhibits excellent compatibility with current cathode materials, including FeF(3) (1.0–4.5 V), Na(3)V(2)(PO(4))(3) (2.0–4.0 V), and S (1.2–2.8 V). This novel Na‐B‐H‐S electrolyte will take a place in mainstream electrolytes because of its advantages in preparation, cost, and compatibility with various cathode materials.