Bio-Inspired Reconstruction of Wood-Chip Electrolytes Enables Triple Zn2+ Confinement for Durable and Sustainable Flexible Zinc-Air Batteries.

Extending the operational lifetime of flexible zinc-air batteries (ZABs) has traditionally focused on improving electrolyte water retention, yet most systems still fail within ∼400 h, revealing that dehydration alone is not the fundamental limitation. Here, a bio-inspired hydrogel electrolyte reconstructed from wood chips overcomes this bottleneck by separating cellulose and lignin: cellulose forms a hydrated network while the extracted lignin is re-applied as an outer water-retentive layer, mimicking the hierarchical fiber-bark architecture of plants. Beyond hydration, the electrolyte implements triple Zn2+ confinement through phosphate-based chelators, dynamic Schiff-base coordination, and polymeric domains, stabilizing Zn2+, suppressing ZnO accumulation, and maintaining interfacial reaction equilibrium at the zinc anode. Flexible ZABs incorporating this electrolyte deliver high power density (124.9 mW cm-2), robust mechanical adaptability, and extended cycling up to 600 h at 1 mA cm-2, while remaining operational under low-temperature and dry conditions. Fully biodegradable and derived from abundant biomass, this system demonstrates that durability arises from hierarchical ion regulation and reaction-equilibrium control rather than water retention alone, providing mechanistic insight into flexible ZABs failure. This work establishes a framework in which biomass valorization and bio-inspired hierarchical design enable durable, high-performance, and environmentally sustainable flexible energy storage.