Achieving high-durability aqueous Zn-ion batteries enabled by reanimating inactive Zn on Zn anodes

The heavy by-products generated on Zn anode surface decrease the active surface of Zn anodes and thus induce uneven Zn deposition, seriously reducing the service life of aqueous Zn-ion batteries (AZIBs). Herein, we propose an elimination strategy enabled by the coordination chemistry to dissolve the main by-products (Zn₄SO₄(OH)₆·xH₂O). Urea as a proof-of-concept has been applied as the reactivator in the electrolyte to catalytically produce highly active NH₃ on the surface of the by-products. Then the NH₃ can powerfully coordinate with the Zn²⁺ ion in the by-products to form the soluble complex [Zn(NH₃)₄]²⁺. Consequently, the proposed electrolyte can not only lead to the timely decomposition of the by-products to prevent the Zn anode from inactivation during cycling, but also repair the waste Zn anodes for reutilization. The action mechanism has been systematically demonstrated via theoretical simulation and experimental study. As a result, the high durability with ultrahigh cumulative capacity of 10,600 mAh cm^-2 for the Zn||Zn symmetric cell has been achieved at 40 mA cm^-2. Particularly, the dead Zn||Zn symmetric cells and Zn||LiFePO₄ full cells have been successfully reactivated. This study lights a new route to extend the cell lifespan and reuse waste Zn-ion batteries.