Zwitterion‐Separated Ion Pair Dominated Additive‐Electrolyte Structure for Ultra‐Stable Aqueous Zinc Ion Batteries

Abstract Aqueous zinc ion batteries (AZIBs) are promising for large‐scale energy storage due to the advantages of high safety, high theoretical capacity, and cost‐effectiveness. However, the stability of AZIBs is poor (generally 50–100 cycles) at low current densities due to side reactions. Here, choline glycerophosphate (CGP) is introduced as a zwitterion additive to improve performance of AZIBs. The CGP helps to form a new solvated structure of Zn 2+ , named zwitterion‐separated ion pair (ZSIP) structure that can link OTf − ion and repel H 2 O molecular. In addition, CGP can be adsorbed on anode to suppress formation of by‐products Zn x OTf y (OH) 2x‐y ·nH 2 O, and on cathode to inhibit Zn 3 (OH) 2 V 2 O 7 ·2H 2 O phase generation. Consequently, the Zn||Cu cell shows an excellent average Coulombic efficiency of 99.79% over 800 cycles at 1 mA cm −2 and 0.5 mAh cm −2 . Impressively, the Zn//NH 4 V 4 O 10 battery demonstrates exceptional capacity retention of 95% along with a high specific capacity of 409.3 mAh g −1 after 350 cycles under a trickle (dis)charge process (0.2 A g −1 ) and an ultra‐long lifespan of 14 000 cycles at 5 A g −1 along with a high specific capacity of 217 mAh g −1 . The concept of ZSIP opens a new avenue for developing aqueous batteries with high performance and long stability in the future.