Lithium ion mediated interfacial transfer and solvation structure enable stable zinc-alloying interface for aqueous zinc battery

Abstract

Nucleation regulation of zinc (Zn) by Zn-alloying interfaces holds great promise for stabilizing Zn electrodes. However, in aqueous Zn batteries (AZBs), the passivation of Zn-alloying interfaces caused by an uneven alloying process and H₂O-enriched environment hinders their ability for sustainable Zn stabilization. Herein, a bi-functional strategy via lithium (Li) ion mediated interfacial transfer and solvation structure is proposed to address the passivation of the Zn-alloying interface, by introducing the Li bis(fluorosulfonyl)imide (LiFSI) additive in ZnSO₄ aqueous electrolyte. Owing to the lower reduction potential of Li⁺ than that of Zn²⁺, the dissociated Li⁺ can retain its ionic state during Zn electroplating at the electrode surface, and engender an electrostatic shielding effect to homogenize the Zn²⁺ transfer as well as the Zn-alloying process. Furthermore, compared with other anions such as SO₄²⁻ and NO₃⁻, the FSI⁻ can cooperate with Li⁺ to form a FSI⁻ assisted Li⁺ solvation sheath in the ZnSO₄ aqueous electrolyte, which induces a solvation competition by attracting H₂O molecules from the Zn²⁺ solvation sheath, thereby preventing the co-decomposition of water dragged by Zn²⁺ during electroplating. This strategy greatly enhances the ability of the Zn-alloying interface for long-lasting Zn protection, affording Zn electrodes for stable operation of full Zn batteries at high cycling rates up to 10C.