Sulfolane as an additive to regulate Zn anode in aqueous Zn-ion batteries

Aqueous Zn-ion batteries (AZIBs) have attracted strong attention for widespread applications because of their safety, cheapness and ecological amiability. Nevertheless, challenges exist at the Zn anode such as the side reactions. Here, a small amount of sulfolane (SL) (1 vol%) was added into the typical ZnSO4 electrolyte as an additive. Detailed studies shown that SL adjusts the solvation structure of Zn2+, reduces the water activity and regulates the Zn deposition. Consequently, the side reactions are suppressed. Therefore, with only addition of 1% SL, the symmetric cells exhibit long cycling lifespan of more than 2000 h and high Coulombic efficiency of 99.7% at 1 mA cm−2 and 1 mAh cm−2. Even under harsh conditions of 5 mA cm−2 and 5 mAh cm−2, the Zn anode still displays long cycling performance of 1000 h. Furthermore, Zn||MnO2 full batteries with SL/ZnSO4 electrolyte shows a high capacity of about 120 mAh g−1 after 500 cycles at 0.5 A g−1.