Tiny‐Ligand Solvation Electrolyte Enabled Fast‐charging Aqueous Batteries

The H‐bond network among H2O molecules enables ultrafast diffusion of H+ and OH‐ via a hopping mechanism, making aqueous batteries attractive competitors for next‐generation fast‐charging energy storages. Ideal aqueous electrolyte for the widely used lithium‐ion batteries is expected to have the wide electrochemical stability window (>5 volts), fast charging (≤15 minutes) without gas evolution, and low cost. However, the hydrogen evolution reaction (HER) associated with narrow voltage window of water (1.23 V) limits their practical applications. Herein, we built a new guideline for designing tiny‐ligand electrolytes by utilizing sterically hindered groups with low binding energy. Cosolvent tetraethyl orthocarbonate (TEOC), with large‐sized ethoxy groups and hydrogen‐bond‐captured ability, forces free H2O and anion TFSI‐ into the Li+ first solvation shell. Hence, inhibition of HER takes place by means of immobilized H2O activity and formation of hydrogen‐bonding networks—C‐O···H between TEOC and H2O. This unique structure with ultra‐small sheath volume thereby facilitates the formation of LiF‐rich SEI and fast ion‐conduction. The lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in TEOC/H2O electrolyte exhibits wide electrochemical window of 5.7 V, enabling LiMn2O4/Li4Ti5O12 pouch cells to achieve 1200 cycles under rapid 10 C rate. This engineering of tiny‐ligand solvation opens new pathways for developing advanced electrolyte that balance performance with sustainability.