Hybrid working mechanism enables highly reversible Zn electrodes

Abstract

Zn dendrite growth and water-related side reactions have been criticized to hinder actual applications of aqueous Zn-ion batteries. To address these issues, a series of Zn interfacial modifications of building solid/electrolyte interphase (SEI) and nucleation layers have been widely proposed, however, their effectiveness remains debatable. Here, we report a boron nitride (BN)/Nafion layer on the Zn surface to efficiently solve Zn problems through combining the hybrid working mechanisms of SEI and nucleation layers. In our protective layer, Nafion exhibits the SEI mechanism by blocking water from the Zn surface and providing abundant channels for rapid Zn²⁺ transmission, whilst BN nanosheets induce Zn deposition underneath with a preferred (002) orientation. Accordingly, dendrite-free and side-reaction-free Zn electrode with (002) deposition under the protective layer is realized for the first time, as reflected by its high reversibility with average Coulombic efficiency of 99.2% for > 3000 ​h. The protected Zn electrode also shows excellent performance in full cells when coupling with polyaniline cathode under the strict condition of lean electrolyte addition. This work highlights insights for designing highly reversible metal electrodes towards practical applications.