Fabrication of high Li:water molar ratio electrolytes for lithium-ion batteries

Abstract

Hydrous electrolytes with high electrochemical potentials were obtained by hydrating water molecules into solutes to form high Li:water molar ratio electrolytes (HMRE). Solid polyethylene glycol (PEG) were employed to enhance the molar ratio of Li+ to water in the electrolytes while reducing the consumption of Li-salt. The obtained mole ratio of Li+ to water molecules in the hydrous electrolytes was greater than 1:1; however, the mass fraction of Li-salt was reduced to 61% (approximately 5.5 mol/kg, based on water and PEG). Compared with that of water-in-salt electrolytes, the mass fraction of Li-salt could be remarkably reduced by adding solid PEG. The electrochemical stability of the electrolytes improved considerably because of the strong hydration of Li+ by the water molecules. A beneficial passivation effect, arising from the decomposition of the electrolyte, at a wide potential window was observed.