Dextran: A Multifunctional and Universal Electrolyte Additive for Aqueous Zn Ion Batteries

Abstract

The aqueous Zn ion battery (ZIB) is a potentially sustainable energy storage device. However, its performance is still far from satisfactory. Herein, it is demonstrated that a branched sugar, dextran, widely used in eyedrop products to relieve irritated eyes, is a multifunctional and universal electrolyte additive to enable high‐performance ZIBs. Experimental and theoretical results reveal that dextran has four functions: forming a surface protective layer to minimize side reactions, facilitating stepwise [Zn(H2O)6]2+ desolvation, preferably adsorbing on Zn(0002) planes to supply desolvated Zn2+ and homogenizing electric field. These functions are universally observed in Zn(CF3SO3)2, ZnSO4, Zn(ClO4)2, and ZnCl2 aqueous electrolytes. As demonstrations for practical applications, Zn anodes deliver Coulombic efficiency of 99.97% after 3400 cycles in an electrolyte with 50 mg mL‒1 of dextran and cumulative plating capacity of 3400 mAh cm‒2 at 5 mA cm‒2. Zn//V2O5 full cells with a low negative/positive electrode capacity ratio of 2.18 can be stably cycled over 138 cycles at 1 A g‒1. Pouch full cells can work under mechanical bending conditions. Zn//polyaniline full cells can cycle steadily for 3000 cycles at 0.5 A g‒1 at −10 °C. Dextran shows excellent potential as a low‐cost and non‐toxic electrolyte additive to enable safe and reliable ZIBs.

Bio‐Inspired Trace Hydroxyl‐Rich Electrolyte Additives for High‐Rate and Stable Zn‐Ion Batteries at Low Temperatures

“…However, they only work well at room temperature due to the solidified electrolyte with limited Zn 2+ de‐solvation processes at low temperatures [22–25] . To promote low‐temperature performance, ZnCl 2 ‐based electrolytes have been reported, which effectively break the hydrogen bond and obtain a low freezing point [26–28] . For example, Chen et al [19] .…”

“…[22][23][24][25] To promote low-temperature performance, ZnCl 2 -based electrolytes have been reported, which effectively break the hydrogen bond and obtain a low freezing point. [26][27][28] For example, Chen et al [19] determined a suitable concentration of 7.5 M ZnCl 2 electrolyte by adjusting the internal structure to reduce the freezing point. However, due to the additional reaction between Cl À ions and active H 2 O molecules in the Zn 2 + solvation layer (e.g., [Zn(H 2 O) 6 ] 2 + , [Zn(H 2 O) 2 Cl 4 ] 2À ), the Zn anode experiences exaggeratedly corrosion and hydrogen evolution reaction (HER) issues, [29][30][31] thus stable cycling performance can only be achieved at low current densities (e.g., 0.2 mA cm À 2 ).…”

Solvation structure regulation of an organic small molecule additive for dendrite-free aqueous zinc-ion batteries

“…22 Considering the above difficulties, it would be more practical to explore suitable electrolyte additives to inhibit the formation of dendrites and to improve the reversibility of the Zn anode. 23–26 Currently, the commonly used electrolyte additives for aqueous zinc-ion batteries can be categorized into four types, including ionic, organic, inorganic, and metallic additives. 27,28 Among them, organic additives have attracted wide attention due to their high solubility in aqueous solution and unique regulation mechanisms.…”

A Fluorinated Solid‐state‐electrolyte Interface Layer Guiding Fast Zinc‐ion Oriented Deposition in Aqueous Zinc‐ion Batteries

“…Various strategies have been developed to solve those problems with Zn anodes, and traditional strategies mainly include electrolyte modulation and Zn anode interface design [7a,b] . The electrolyte modulation mainly changes the solvation structure of zinc ions by introducing electrolyte additives, [8a,b] such as ethylene glycol, [9] glycine, [10] pyridine, [11] etc. This approach reduces the content of water molecules coordinating with zinc ions, minimizing the HER on Zn anode surface during the deposition of zinc ions [12] .…”