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

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 Zn²⁺ flux and suppress concentration polarization on zinc metal surface, while sulfonate functionalities promote [Zn(H₂O)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-I₂ 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. © 2026 Wiley-VCH GmbH.