Gaseous SO2 Additive for High-Energy-Density Li-Ion Battery.

Electrolyte additive engineering is pivotal for suppressing interfacial degradation and enhancing the cycling stability of high-energy-density batteries. However, conventional solid or liquid additives face inherent limitations such as high production costs, chemical instability, and inefficient interfacial passivation, restricting their practical application. Here, we propose an electrolyte engineering strategy that makes sustainable use of sulfur dioxide (SO2), an industrial waste-derived gas, as a dual-functional gaseous additive. Owing to its ultrahigh reduction potential (2.6 V versus Li+/Li), which exceeds that of most known additives, and a low oxidation potential, SO2 promotes the in situ formation of sulfur-containing interphases on both electrodes through preferential electrochemical reactions, thereby effectively suppressing parasitic electrolyte decomposition. SO2 enables 4.4 V-class AG || NCM613 pouch cells to achieve exceptional cyclability exceeding 800 cycles with 88.2% capacity retention, along with outstanding temperature tolerance from -30 °C to 45 °C. This strategy also demonstrates universal applicability, yielding a long life of 800 cycles for Ah-level 4.3 V-class Si/C || NCM811 pouch cells. Furthermore, this approach alleviates electrolyte discoloration, extending shelf life while reducing cost and energy consumption. This work establishes a sustainable circular economy model by valorizing industrial exhaust into high-value battery components, bridging environmental stewardship with next-generation energy storage innovation.