Wood‐Derived Separators: Cost‐Centric Material Design for Zinc‐Metal Batteries

ABSTRACT Aqueous zinc‐metal batteries (AZMBs) are regarded as a promising solution for grid‐scale energy storage owing to intrinsic safety, high energy density, and low cost. Yet, their commercialization remains limited by an unexpected bottleneck: a lack of decisive cost advantage over commercialized lithium‐ion batteries. Here, we reveal that the separator—rather than the electrode materials—dominates the cell‐level cost of AZMBs, accounting for half of the total cost in practical pouch cells. To overcome this constraint, we introduce a wood‐derived separator that synergistically integrates cost reduction with performance optimization. By delignifying and sulfonating natural wood, the resulting wood‐derived separator preserves vertically aligned, low‐tortuosity microchannels that homogenize/stabilize Zn 2+ flux and suppress concentration polarization on zinc metal surface, while sulfonate functionalities promote [Zn(H 2 O) 6 ] 2+ desolvation and inhibit hydrogen evolution. Consequently, zinc‐metal half‐cells exhibit dendrite‐free cycling over 750 h under harsh conditions (DOD: 50%, 10 mA cm −2 /5 mAh cm −2 ), while full Zn‐I 2 cells deliver 6300 stable cycles at 1 A g −1 with a capacity retention of 91.8%. Notably, this strategy substantially cuts separator costs relative to commercial glass fiber (CGF) separators and potentially lowers the total battery cost by approximately half based on projected component‐level cost analysis, offering a cost‐effective route to boost AZMB competitiveness.