Multiscale Interfacial Regulation of Zn-V₂O₅ Pouch Cell via Ultrathin Molecular-Engineered Separator

Rechargeable aqueous zinc batteries (RAZBs) suffer from the structural degradation of the layered oxide cathode, parasitic side reaction on the Zn foil as well as often-overlooked self-discharge phenomenon at the elevated temperatures. Herein, this study presents a thin-layer (9 µm) molecular-engineered separator strategy to achieve the concurrent shelf life, cycling endurance, as well as the practical energy density for the RAZBs prototype. On the face-to-cathode side, the biphthalic anhydride is anchored onto the polyethylene separator substrate (PE) via a robotic arm-controlled spray-coating method, inhibiting the spontaneous vanadium dissolution and shuttle at both the dynamic cycling or static high-temperature storage; meanwhile the 3,3′-diamino-4,4′-dihydroxydiphenyl sulfone molecular tailoring on the face-to-anode side provides ion-sieving capability to repel detrimental SO₄²⁻, yet guiding uniform Zn²⁺ influx and preferential deposits accumulation along the (002) crystallographic orientation even at the extreme deposition scenario (20 mA cm⁻², 20 mAh cm⁻²). Upon the layer-stacked assembly of the V₂O₅ cathode (2.0 mAh cm⁻²), molecular-engineered separator as well as the Zn foil (20 µm), the 0.78 Ah pouch-format prototype exhibits the superior volumetric/gravimetric energy densities of 133.3 Wh L⁻¹/71.4 Wh kg⁻¹ and extreme power output (444.3 W L⁻¹/238.0 W kg⁻¹).