Negative electrode degradation induced by two-stage zinc plating and its recovery in zinc batteries

Controlling the morphology of Zinc (Zn) deposits is an effective strategy to produce stable Zn-metal batteries. However, the degradation of Zn negative electrodes and changes in their morphology remain poorly understood. Here, we show that the Zn plating process has two distinct stages. The first being the formation of relatively dense, lumpy Zn, while the second involves the formation of porous mossy Zn on its protrusions, which changes into electrochemically inactive dead Zn during stripping. Based on this, we propose a strategy involving a combination of cationic and anionic reagents to revive the dead Zn. The cations create a positively charged inert region on the negative electrode surface for Zn-ion dispersion that inhibits mossy Zn formation, while the anions act as a redox mediator to revive the dead Zn. Consequently, the Zn negative electrode shows a Coulombic efficiency (CE) of 99.7% and stable Zn plating/stripping over 1400 h (10 mA cm^-2 and 10 mAh cm^-2). An Ah-scale pouch cell retains 96.2% capacity after 800 cycles. This work provides key insights into mossy Zn formation and proposes a promising approach for stable Zn-metal batteries.