Sustainable ultra-long cycle life aqueous Zn-I2 battery without ion-selective membrane

Abstract

Rechargeable aqueous zinc-iodine (Zn-I2) batteries are generally in the form of redox flow battery that uses an ion-selective membrane to separate two different electrolytes. The reversible redox reactions of iodine species in the electrolyte play a key role in charge and discharge. If without the ion-selective membrane, the Zn anode would suffer from severe corrosion, and the interaction between Zn and I3– in the cycling process gradually reduces the cell capacity, Coulombic efficiency, and cycle life. Here, a simple and scalable chemical bath deposition method is developed to form an amorphous Se overlayer on the Zn foil, thus remarkably improving its anode performance in aqueous Zn-I2 battery and ruling out the use of ion-selective membrane. Effects of Se deposition time on the anti-corrosion performance, rate performance, capacity, and cycle life are investigated in detail. As a result, the button-type full cell using optimized Zn@Se anode delivers high Coulombic efficiency of 99.4%, high specific capacity of 180 mAh g–1, and ultra-long lifespan over 50,000 cycles with a capacity retention of 82.6%. Pouch type cells are made to demonstrate the efficient suppression of hydrogen gas evolution. To manifest the potential for practical applications, high-capacity cells using plastic boxes are made to drive an electric fan and a robot toy. Mechanism of this amorphous Se overlayer on Zn anode in enhancing the battery performance is discussed.