Chlorination Design for Highly Stable Electrolyte toward High Mass Loading and Long Cycle Life Sodium‐Based Dual‐Ion Battery

Abstract Sodium‐based dual ion batteries (SDIBs) have garnered significant attention as novel energy storage devices offering the advantages of high‐voltage and low‐cost. Nonetheless, conventional electrolytes exhibit low resistance to oxidation and poor compatibility with electrode materials, resulting in rapid battery failure. In this study, for the first time, a chlorination design of electrolytes for SDIB, is proposed. Using ethyl methyl carbonate (EMC) as a representative, chlorine (Cl)‐substituted EMC not only demonstrates increased oxidative stability ascribed to the electron‐withdrawing characteristics of chlorine atom, electrolyte compatibility with both the cathode and anode is also greatly improved by forming Cl‐containing interface layers. Consequently, a discharge capacity of 104.6 mAh g −1 within a voltage range of 3.0–5.0 V is achieved for Na||graphite SDIB that employs a high graphite cathode mass loading of 5.0 mg cm −2 , along with almost no capacity decay after 900 cycles. Notably, the Na||graphite SDIB can be revived for an additional 900 cycles through the replacement of a fresh Na anode. As the mass loading of graphite cathode increased to 10 mg cm −2 , Na||graphite SDIB is still capable of sustaining over 700 times with ≈100% capacity retention. These results mark the best outcome among reported SDIBs. This study corroborates the effectiveness of chlorination design in developing high‐voltage electrolytes and attaining enduring cycle stability of Na‐based energy storage devices.