A carrageenan-induced highly stable Zn anode by regulating interface chemistry

Zinc-ion batteries (ZIBs) are promising on account of the inherent safety, minimal toxicity, cost-effectiveness, and high theoretical capacity. However, the critical issues including the Zn dendrites and side reactions impede their commercial application. Here, we propose green, non-toxic and biological carrageenan (Carr) serving as an electrolyte additive to address the aforementioned issues. Owing to the multifunctional groups, Carr has the capacity to interact with Zn²⁺, thereby modulating the solvation configuration of Zn²⁺ and changing the ion distribution at the electrode-electrolyte interface. Moreover, it can adsorb on the Zn electrode and induce the formation of a solid electrolyte interphase (SEI) consisting of ZnO, ZnS and R-SO₂ species. It contributes to uniform Zn²⁺ ion diffusion and even Zn deposition with the preferable (002) plane. Consequently, the Zn||Zn cells exhibit a stable cycle performance for 800 h at 5 mA cm^-2 and 5 mA h cm^-2. An elevated coulombic efficiency of 99.2% over 1800 cycles is obtained in the Zn||Cu cells using the electrolyte with Carr. Benefitting from the highly stable and reversible Zn anode, the Zn||VO₂ full cell also delivers a high performance in comparison with the bare ZnSO₄ electrolyte, favoring the practical implementation of ZIBs.