Salt Anion Amphiphilicity-Activated Electrolyte Cosolvent Selection Strategy toward Durable Zn Metal Anode

Abstract

One effective solution to inhibit side reactions and Zn dendrite growth in aqueous Zn-ion batteries is to add a cosolvent into the Zn­(CF3SO3)2 electrolyte, which has the potential to form a robust solid electrolyte interface composed of ZnF2 and ZnS. Nevertheless, there is still a lack of discussion on a convenient selection method for cosolvents, which can directly reflect the interactions between solvent and solute to rationally design the electrolyte solvation structure. Herein, logP, where P is the octanol–water partition coefficient, a general parameter to describe the hydrophilicity and lipophilicity of chemicals, is proposed as a standard for selecting cosolvents for Zn­(CF3SO3)2 electrolyte, which is demonstrated by testing seven different types of solvents. The solvent with a logP value similar to that of the salt anion CF3SO3 – can interact with CF3SO3 –, Zn2+, and H2O, leading to a reconstruction of the electrolyte solvation structure. To prove the concept, methyl acetate (MA) is demonstrated as an example due to its similar logP value to that of CF3SO3 –. Both the experimental and theoretical results illustrate that MA molecules not only enter into the solvation shell of CF3SO3 – but also coordinate with Zn2+ or H2O, forming an MA and CF3SO3 – involved core–shell solvation structure. The special solvation structure reduces H2O activity and contributes to forming an anion-induced ZnCO3–ZnF2-rich solid electrolyte interface. As a result, the Zn||Zn cell and Zn||NaV3O8·1.5H2O cell with MA-involved electrolyte exhibit superior performances to that with the MA-free electrolyte. This work provides an insight into electrolyte design via salt anion chemistry for high-performance Zn batteries.

Electric field distribution regulation of a zinc anode toward long cycle life zinc metal batteries

“…At the same time, the fluorinated layer has higher Δ G h for surface reactions, leading to inhibited dendrite growth and HER process. 34,35 The coulombic efficiency of the bare Zn anode and zigzag Zn anode were also measured by assembling Zn‖Cu half-cells at a current density of 0.5 mA cm −2 (Fig. 3c).…”

Weakly solvating aqueous-based electrolyte facilitated by a soft co-solvent for extreme temperature operations of zinc-ion batteries

“…Shi et al constructed a water-poor solvation structure with a soft co-solvent butanone, achieving boosted desolvation kinetics of Zn 2+ and demonstrating a good practical application in large current densities. 22 However, the cycling performance of this electrolyte under low current density (1 mA cm −2 , 1 mA h cm −2 ) in a Zn//Ti cell is not satisfactory, with only 300 cycles reported, which is much lower than other strong co-solvents at the same current density, 14,23,24 such as dimethyl methyl phosphonate (DMMP) (1000 cycles), 24 possibly due to the lack of a protective interphase layer on the anode. Therefore, in addition to boosting the kinetics of Zn 2+ , a soft co-solvent that can enhance the robust SEI formation is favoured.…”

Progress in stabilizing zinc anodes for zinc-ion batteries using electrolyte solvent engineering

“…7e). 69 Solvents with a log P value similar to that of CF 3 SO 3 − can be used to interact with CF 3 SO 3 − , Zn 2+ , and H 2 O to reconfigure the solvated structure of the electrolyte. To demonstrate this concept, methyl acetate (MA) was used as an example because it has a log P value similar to that of CF 3 SO 3 − .…”