Angstrom-Scale Confined Ion Sieve and Accelerator for Efficient Aqueous Zinc Batteries

The commercialization of aqueous zinc-metal batteries (AZMBs) is hindered by dendrite growth caused by uncontrolled Zn²⁺ transport and side reactions involving water and anions. Here, an angstrom-scale confined ion sieve and accelerator is designed using unilamellar Ti_0.87O₂ nanosheets with atomic Ti vacancies (∼3.0 × 3.8 Å) and interlayer spacing (∼3.5 Å) to enable selective Zn²⁺ (∼1.5 Å) transport while blocking H₂O (∼4.0 Å) and SO₄ ^2- (∼5.9 Å). This design facilitates selective Zn²⁺ ion transport with high flux and Zn/SO₄ ^2- selectivity, effectively mitigating water-/anion-induced parasitic reactions at the Zn anode. Consequently, the Ti_0.87O₂@Zn anode exhibits significantly suppressed dendrite growth and parasitic side reactions during repeated Zn plating/stripping, with stable cycle lives exceeding 5000 and 4000 h at 1 and 5 mA cm^-2, respectively. The Ah-level Ti_0.87O₂@Zn//VO₂ pouch cell retains 85.4% of its initial capacity after 300 cycles at 3 A g^-1. This strategy provides a promising interfacial design concept for improving the reversibility of aqueous Zn metal anodes and may inspire the rational design of confined ion-transport interphases for related aqueous battery systems.