Optimization Strategies of Electrolytes for Low‐Temperature Aqueous Batteries

Abstract

Aqueous rechargeable batteries (ARBs) are considered promising electrochemical energy storage systems for grid‐scale applications due to their low cost, high safety, and environmental benignity. With the demand for a wide range of application scenarios, batteries are required to work in various harsh conditions, especially the cold weather. Nevertheless, electrolytes would freeze at extremely low temperatures, resulting in dramatically sluggish kinetics and severe performance degradation. Here, we discuss the behaviors of hydrogen bonds and basic principles of anti‐freezing mechanisms in aqueous electrolytes. Then, we present a systematical review of the optimization strategies of electrolytes for low‐temperature aqueous batteries. Finally, the challenges and promising routes for further development of aqueous low‐temperature electrolytes are provided. This review can serve as a comprehensive reference to boost the further development and practical applications of advanced ARBs operated at low temperatures.

Electrolyte Modulation Strategies for Low‐Temperature Zn Batteries

“…[3b,47] All these methods could break HBs among water molecules and inhibit water-ice transition. [48] Among the various anti-freezing organic solvent additives, EG and glycerol are two typical kinds of polyol solvents that are used as cryoprotectants. [49] Their intensive interactions and free solubility with water impair the interactions among water molecules and inhibit ice crystallization.…”

An inexpensive electrolyte with double-site hydrogen bonding and a regulated Zn2+ solvation structure for aqueous Zn-ion batteries capable of high-rate and ultra-long low-temperature operation

“…17,18 To address these problems, the introduction of hydrogen bonding acceptor or donor substances into aqueous electrolytes which, by coordination with water molecules, restrict the contact of water molecules and break the initial hydrogen bonding networks, can effectively inhibit the freezing of aqueous electrolytes. [19][20][21][22][23] Among them, cations, as typical hydrogen bonding acceptors, can form typical solvated structures via the solvation effect coordinated with water, thus effectively breaking the initial hydrogen bonding networks between the water molecules. [24][25][26][27] However, this strategy always requires significant amounts of cations to fully interact with substantial quantities of water, resulting in aqueous electrolytes with certain concentrations of salt or even ''salt-in-water'', which leads to increased costs and viscosity, drastically affecting the diffusion and storage of ions at low temperatures.…”

High-entropy solvent design enabling a universal electrolyte with a low freezing point for low-temperature aqueous batteries

“…4,5 Utilizing strong interactions between the solute and water molecules is believed to be an effective strategy because solute molecules can coordinate with water molecules and destroy the ordered hydrogen bond network. 6,7 However, this strategy always requires a defined type and concentration of solute, such as 7.5 m (mol kg À1 ) ZnCl 2 , 8 3.5 M (mol L À1 ) Mg(ClO 4 ) 2 + 1 M Zn(ClO 4 ) 2 , 9 and 2 M Zn(CF 3 SO 3 ) 2 , 10 restricting the application of the electrolyte. High-entropy design has been universally applied in materials science, such as high-entropy nanoparticles, which contain more than four elements uniformly mixed into a solid-solution structure.…”