Dual Role of Glass-Fiber Separator Pore Size in Aqueous Zinc-Iodine Batteries: Fast Supply and Cycling Stability

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2026年6月26日

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Jae-Hyuk Cho,
Ho-Jin Lee,
Dae-Kwon Boo,
Jeong-Ho Park,
Ji-Won Jung

摘要

Aqueous Zn–I₂ batteries offer high safety, low cost, and a 211 mAh g⁻¹ theoretical capacity, but the effect of separator grade has not been systematically resolved. We arrange five Whatman glass fiber (GF) grades (A, C, F, D, B; thickness 260–675 μm, mean pore 0.7–2.7 μm) into a 2D matrix in which thickness and pore size decouple naturally, and use the same-thickness pair GF/A versus GF/C at 260 μm (Pair α) as the controlled comparison across EIS, Tafel, symmetric-cell rate, full-cell rate, and long-term cycling measurements. The electrolyte resistance R_s increases monotonically with thickness (GF/A 0.24 to GF/B 0.49 Ω), matching the Bruggeman–Ohm relation. The Tafel exchange current density j₀ orders as GF/D 1.10 > GF/A 0.72 > GF/C 0.59 > GF/B 0.45 > GF/F 0.23 mA cm⁻², following the mean-pore ranking but not the thickness ranking. This is the fast-supply effect, in which larger pores deliver Zn²⁺ to the anode faster, raising the apparent kinetics measured in a single voltage sweep. Repeated plate/strip cycling of the same Pair α gives the opposite ordering. At 0.7 A g⁻¹ in the full cell, GF/C sustains 135.7 mAh g⁻¹ while GF/A collapses to 69.5 mAh g⁻¹, because smaller pores drive more uniform Zn nucleation cycle after cycle, which we define as the uniform-deposition effect. The two effects share the same pore variable but operate in different regimes. Fast-supply dominates the single-sweep regime such as LSV; uniform-deposition dominates the multi-cycle plate/strip regime. Long-term cycling of GF/B confirms this, with 86.7% capacity retention over 900 cycles. Building on this dual-role pore framework, we propose “the smallest pore at acceptable thickness” as a separator design principle for high-rate, long-life Zn–I₂ applications.

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