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

Abstract

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.