A high energy efficiency and long life aqueous Zn-I2 battery
Herein, a high energy efficiency and long life aqueous Zn-I2 battery based on activated carbon encapsulated I2 (I2@C-50) cathode is reported. It is found that the optimized electrolyte of Zn(CF3SO3)2 can significantly boost the initial coulombic efficiency from 61.1% to 91.3% due to the coordination effect, which accounts for the high energy efficiency of the battery. Moreover, the discovery of the in-situ formed solid electrolyte interphase (SEI) film on Zn surface can effectively stabilize Zn stripping/plating and ensure the long cycling of aqueous Zn-I2 battery. Besides, the activated carbon host with large surface area, strong adsorption and spatial confinement suppresses the loss of active materials. As a result, the I2@C-50 cathode realizes a capacity of 210 mAh g-1 and high energy efficiency of 96.7% at 0.1 A g-1, and keeps a capacity retention of 66% after 10,000 cycles at 5 A g-1. In addition, pouch batteries with different sizes also demonstrate their feasibility in practical application. The presented results of this work provide the insights on the electrode, electrolyte and interface engineering to design high performance aqueous batteries.