Boosting Zn metal anode stability : from fundamental science to design principles

Abstract

The development of Zn metal anodes suffers from several critical issues, including dendrite growth, hydrogen evolution reaction, and corrosion. Extensive efforts have been applied through ameliorating electrode structures, electrode/separator interfaces, and electrolyte formulations. We deviate from the specific approaches and discuss the roots of the existing problems to exploit the fundamental science behind the proposed approaches. We divide the Zn deposition process into four steps, that is, mass transfer in the bulk electrolyte, desolvation on the electrode surface, charge transfer for the Zn2+ reduction, and Zn cluster formation through the electro-crystallization. It can be seen that all the reported strategies for improving Zn anode stability deal with at least one of these steps, thereby enhancing the understanding of dendrite formation and benefiting the rational design to circumvent the issue. We also scrutinize the previous attempts to suppress the side reactions through water activity reduction and electrode passivation to raise battery reliability. Finally, we propose possible solutions to the remaining but urgent challenges toward low-cost, high-safety, and long-lifespan Zn metal batteries.