Electrolyte Engineering with TFA- Anion-Rich Solvation Structure to Construct Highly Stable Zn2+/Na+ Dual-Salt Batteries

Abstract

Electrolyte engineering is recognized as an effective technique for high-performance aqueous zinc-ion rechargeable batteries, addressing difficulties such as free water decomposition, zinc anode corrosion, and zinc dendrite growth. Different from traditional strategies in aqueous electrolyte systems, this work focuses on organic electrolytes involving zinc trifluoroacetate hydrate (Zn(TFA)₂·xH₂O), sodium trifluoroacetate (NaTFA) dual-salt and acetonitrile (AN) solvent, in which trifluoroacetate anions (TFA^- anions) have strong affinity toward zinc ions to form anion-rich solvates, thus inducing an inorganic-rich solid electrolyte interphase (SEI) to protect Zn from dendrite growth and side reactions. The Zn anode manifests long-term cycling over 2400 h at a current density of 0.5 mA cm^-2 with a high Coulombic efficiency (CE) of 99.75%, showing an areal capacity as high as 5 mAh cm^-2. Owing to the high reversibility of the sodium ions intercalation/deintercalation process in Na₂MnFe(CN)₆, the Zn//Na₂MnFe(CN)₆ full cells with the dual-salt electrolyte perform much better in terms of capacity retention than a device with Zn(TFA)₂/AN electrolyte. This approach may open a new avenue for efficient zinc-ion rechargeable batteries via developing organic electrolytes.

Keywords: Zn2+/Na+ dual‐salt batteries; anion‐rich solvation structure; electrolyte engineering; stabilized zinc anodes.