Regulating Zn²⁺/H⁺ selectivity through functional group design of separators for long-lifespan aqueous zinc batteries

Zn anodes in aqueous rechargeable zinc batteries (AZBs) are plagued by irreversibility issues stemming from dendrite growth, hydrogen evolution, and corrosion. The design of separator offers a promising approach to enhance the reversibility of Zn anodes, but a universal strategy for rational separator design remains elusive. In this study, we propose a comprehensive design principle that takes into account the selective binding with Zn²⁺, H⁺ and H₂O, and further suggest that separators should ideally exhibit strong binding strength with H⁺ and H₂O but weak with Zn²⁺. We explore four typical scenarios based on varying binding strengths and identify polyethersulfone (PES) as a highly promising separator through screening of various commercial separators. Both experiment and theoretical calculations reveal that PES effectively regulates the transfer of Zn²⁺, H⁺ and H₂O, thereby concurrently suppressing dendrite growth, hydrogen evolution, and corrosion. As a result, the Zn‖Zn symmetric battery can operate for over 4000 h at 1 mA cm^-2 and 1 mA h cm^-2. Furthermore, the full battery can deliver an impressive lifespan of over 6400 cycles at 3 A g^-1. This work not only introduces a new separator for high-performance AZBs but also provides guiding principles for functional separator design.