Advances on liquid electrolytes for Li-ion and Li metal batteries

Summary Battery materials have been extensively studied in the past decades aiming to improve their capacity, energy density and power density. In this opinion review, materials that are used as liquid electrolytes are discussed, from organic, including ionic liquids, to aqueous-based ones. Strategies such as fluorinated organic solvents and low-solvating organic solvents are highlighted, showing the recent progress, and their impact on Li plating/stripping and on battery performance. Aqueous electrolyte with molecular crowding is also discussed, where Li+ solvation is controlled to be mostly by anions, which changes the nature of the solid electrolyte interphase. This opinion review aims to highlight the past two years of important reports on electrolyte for Li-ion and Li metal batteries.