Bio‐Inspired Reconstruction of Wood‐Chip Electrolytes Enables Triple Zn 2+ 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 Zn 2+ confinement through phosphate‐based chelators, dynamic Schiff‐base coordination, and polymeric domains, stabilizing Zn 2+ , 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.