Concentrated Lithium Dodecyl Sulfate Aqueous Electrolytes: Utilizing Self‐Assembly and Interfacial Adsorption for Aqueous Li‐ion Batteries

Abstract Since aqueous lithium‐ion batteries (LIBs) were first proposed, electrolyte design has been intensively studied. We report a simple anionic surfactant, i. e., a lithium dodecyl sulfate (LiDS)‐based aqueous electrolyte, capable of enhancing the Li ion transport properties in the bulk and protecting the electrode at the interface. The self‐assembly of DS anions into micelles effectively limited anion diffusion, enabling nearly single Li‐ion conduction in the bulk electrolyte. The interfacial adsorption of DS molecules formed a hydrophobic layer at the electrolyte/electrode interface under the electric field of the electric double layer, excluding water molecules from the interface. Consequently, the electrochemical window of the aqueous electrolyte was expanded to 3.0 V. This electrolyte improved the cycle performance and rate capability of the LiFePO 4 /LiTi 2 (PO 4 ) 3 full‐cell compared to a 1.0 mol dm −3 Li 2 SO 4 /H 2 O reference electrolyte. These results provide a new twist in the design of liquid electrolytes for aqueous LIBs.