Solvation Regulation of Flame‐Retardant Bromine‐Based Electrolyte Enables Stable Cycling Dual‐Ion Battery

Abstract

ABSTRACT Dual‐ion batteries (DIBs) have emerged as an attractive electrochemical energy storage technology owing to the distinctive advantages of cost‐effectiveness, high operating voltage, and high power density. Nevertheless, conventional electrolytes face critical challenges including insufficient oxidation stability and severe flammability. Herein, a brominated electrolyte design for DIBs is proposed for the first time, and as an example of this strategy, ethyl acetate (EA) is selected for bromination. As a result, effectively suppressed electrolyte decomposition under high voltage, enhanced electrolyte/electrode compatibility by forming LiF/LiBr‐rich interfaces, and anti‐corrosive capability toward the aluminum current collector are simultaneously achieved with bromoethyl acetate (Br‐EA) based electrolyte. Besides, compared to fluorine‐based and chlorine‐based electrolytes, bromine‐based electrolyte demonstrates superior flame‐retardancy. With the developed 6.0 m LiFSI Br‐EA:DMC (1:1, v/v) electrolyte, the dual‐graphite battery maintains 85.6% capacity retention after 1000 cycles, among the best reported results; the pouch cell employing this electrolyte retains 79.8% of initial discharge capacity over 500 cycles, validating its practical feasibility. This research work establishes bromination design as a groundbreaking paradigm for high‐voltage and high‐safety battery systems.