Geometry-driven molecular design provides a promising route for controlling electrode/electrolyte interfaces in aqueous zinc-ion batteries (AZIBs), yet rational additive selection remains challenging. This study demonstrates the effectiveness of molecular point group theory as a screening principle for high-performance electrolyte additives. The tetrahedral quaternary phosphonium cation (P4444+) stands out for its inherently high Td symmetry and localized polarization, compared with asymmetric cations. Combined experimental and theoretical results reveal that P4444+ maintains a stereochemically locked Td → C3v adsorption geometry, assembling into a uniform and gradient protective layer (cation-rich inner/anion-rich outer) that displaces interfacial water. This ordered interphase transforms in situ into a ZnP/ZnF2-enriched solid electrolyte interphase (SEI), effectively suppressing hydrogen evolution, mitigating corrosion, and channeling Zn2+ flux into planar and dendrite-free deposition. Consequently, Zn//Zn cells with P4444+ additives achieve extended cycle life exceeding 3000 h at 1 mA cm-2 and 1200 h at 5 mA cm-2, while Zn//polyaniline (PANI) full cells maintain 86.2% capacity after 2000 cycles at 1.0 A g-1. These findings reveal a strong correlation between molecular symmetry and interfacial stability, which offers insights for next-generation additive design and advancing high-performance, durable AZIBs.
Xu et al. (Wed,) studied this question.
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