Achieving highly reversible zinc metal anode via surface termination chemistry.

An oxidation layer on a Zn surface is considered to play a negative role in hindering the practical applications of aqueous zinc ion batteries (AZBs). Herein, we demonstrate the importance of Zn-surface termination on the overall electrochemical behavior of AZBs by revisiting the well-known bottleneck issues. Experimental characterizations in conjugation with theoretical calculations reveal that the formation of a dense Zn(OH)SO·xHO (ZSH) layer from the well-designed surface-oxide termination layer improves the interface stability of the Zn anode and reduces the dehydration energy of Zn(HO), thereby accelerating the interface transport kinetics of Zn. Moreover, instead of directly diffusing over the ZSH layer, a new "edge dehydration-along edge transfer" mechanism of Zn is discovered. Owing to the presence of a Zn anode with a ZnO-derived ZSH layer, an ultrahigh stability of over 1200 h with a high cumulative-plated capacity of 6.24mAh cm is achieved with a symmetrical cell. Furthermore, high cycling stability (over 1000 cycles) and Coulombic efficiency (99.07%) are obtained in the entire AZBs with a MnO cathode. An understanding of the oxygen surface termination mechanism is beneficial to Zn-anode protection and is a timely forward step toward the long-pursued practical application of AZBs.