Upcycling waste for next-generation sulfur batteries: Strategies for a circular energy future

The global transition toward sustainable energy storage positions sulfur-based batteries (Li-S, Na-S, Zn-S) as superior alternatives to lithium-ion systems. However, the polysulfide shuttle effect and sluggish redox kinetics remain primary obstacles. This review synthesizes recent advancements in valorizing diverse waste streams, agricultural residues, industrial by-products, and municipal plastics, as functional components for high-performance sulfur batteries. Data reveals that biomass-derived carbon hosts accommodate sulfur loadings of 60–90% via ultra-high specific surface areas (up to 4220 m 2 /g), delivering initial capacities between 1200 and 1700 mAh/g. Analysis identifies a strategic shift from physical confinement to active chemical management; engineered hosts from industrial and medical waste, integrated with single/dual-atom catalysts (Co, Zn), minimize capacity decay to 0.006–0.094% per cycle. Furthermore, waste-derived frameworks enable alternative chemistries to exceed 1500 mAh/g through quasi-solid-state conversion. While laboratory performance is maturing, future research must prioritize lean electrolyte conditions (E/S < 3 μL/mg) and industrial-grade areal loadings (≈ 8 mAh/cm 2 ). By aligning waste-to-carbon strategies with life cycle assessments, these storage solutions offer a dual pathway for high-efficiency power delivery and environmental remediation within a circular economy. • Waste hosts achieve 60–90 wt% S via architectures up to 4220 m 2 /g. • Initial discharge capacities reach 1700.54 mAh/g, near theoretical limits. • Single-atom catalysts and doping reduce decay to 0.006% per cycle. • Binder-free hosts push areal capacities > 8 mAh/cm 2 , exceeding targets. • Na-S/Zn-S systems exceed 1500 mAh/g via micropore-driven conversion.