Electrolyte Design for High‐Voltage Lithium‐Metal Batteries with Synthetic Sulfonamide‐Based Solvent and Electrochemically Active Additives

Abstract Considering practical viability, Li‐metal battery electrolytes should be formulated by tuning solvent composition similar to electrolyte systems for Li‐ion batteries to enable the facile salt‐dissociation, ion‐conduction, and introduction of sacrificial additives for building stable electrode–electrolyte interfaces. Although 1,2‐dimethoxyethane with a high‐donor number enables the implementation of ionic compounds as effective interface modifiers, its ubiquitous usage is limited by its low‐oxidation durability and high‐volatility. Regulation of the solvation structure and construction of well‐structured interfacial layers ensure the potential strength of electrolytes in both Li‐metal and LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811). This study reports the build‐up of multilayer solid‐electrolyte interphase by utilizing different electron‐accepting tendencies of lithium difluoro(bisoxalato) phosphate (LiDFBP), lithium nitrate, and synthetic 1‐((trifluoromethyl)sulfonyl)piperidine. Furthermore, a well‐structured cathode–electrolyte interface from LiDFBP effectively addresses the issues with NCM811. The developed electrolyte based on a framework of highly‐ and weakly‐solvating solvents with interface modifiers enables the operation of Li|NCM811 cells with a high areal capacity cathode (4.3 mAh cm⁻²) at 4.4 V versus Li/Li⁺.