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Low temperature aqueous batteries (LT-ABs) have attracted extensive attention recent years. The LT-ABs suffer from electrolyte freezing, slow ionic diffusion and sluggish interfacial redox kinetics at low temperature. In this review, we discuss physicochemical properties of aqueous electrolytes in terms of phase diagram, ion diffusion and interfacial redox kinetics to guide the design of low temperature aqueous electrolytes (LT-AEs). Firstly, the characteristics of equilibrium and nonequilibrium phase diagrams are introduced to analyze the antifreezing mechanisms and propose design strategies for LT-AEs. Then, the temperature/concentration/charge carrier dependence conductivity characteristics in aqueous electrolytes are reviewed to comprehend and regulate the ion diffusion kinetics. Moreover, we introduce interfacial studies in aqueous and non-aqueous batteries and propose potential improvement strategies for interfacial redox kinetics in LT-ABs. Finally, we summarize design strategies of LT-AEs for developing high performance LT-ABs.

Using cost-effective and environmentally friendly molecular crowding agents to replace highly concentrated salts is a promising strategy to suppress water decomposition in electrochemical energy storage devices. However, the lack of comprehensive understanding on how a crowding agent structure affects the key properties of electrolyte prevents rational design of molecular crowding electrolyte for high-power and high-voltage aqueous batteries. Here, we investigated how the terminal group and the chain length of the crowding agent affect the conductivity and the voltage window. On the basis of the design principles revealed, we developed a new crowding agent, polyethylene glycol dimethyl ether (PEGDME) 450, demonstrating 3 times higher conductivity (2.4 mS cm −1 vs 0.8 mS cm −1 ) than state-of-the-art polyethylene glycol (PEG) 400 without sacrificing the voltage window (3.2 V). A high-power and high-voltage aqueous Li 4 Ti 5 O 12 / LiMn 2 O 4 cells with this new electrolyte operated (5 C, 72 Wh kg −1 vs 10 Wh kg −1 PEG400) for 800 cycles. This work demonstrates a universal strategy for advanced aqueous electrolyte design and high-performance batteries.

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Non-nucleophilic and non-fluorinated compounds are the most important class of solvent to enable sustainable rechargeable magnesium (Mg) batteries, however, they suffer from poor stability due to the formation of unstable...