The high-voltage stability of electrolytes profoundly determines electrochemical reactions, which is still one of the major obstacles for developing advanced Al-ion batteries (AIBs). Herein, a fluorine-adjustment strategy is proposed to improve the high-voltage stability of a low-cost AlCl3/acetamide (AcA) deep eutectic solvent electrolyte. By using a fluorine-substituted AcA additive, the AlCl3/AcA electrolyte exhibits a lifted oxidation onset potential from 2.21 to 2.78 V versus Al3+/Al. Based on a series of structural investigations, it is found that the additive can adjust the coordination configurations and improve the anti-oxidation capability of electrolytes. Moreover, the additive induces an F-rich interphase layer, which can stabilize the plating/stripping reactions of Al electrode with accelerated kinetics. Based on the optimized electrolyte, a high-voltage Al–S battery relying on the S cationic redox shows good performance with little voltage fading for 300 cycles. This study provides important insights into the exploration of high-performance and low-cost electrolytes for AIBs.