Constructing Gradient Separator to Stabilize Bi‐electrodes Toward High‐Performance Zn Metal Batteries

Abstract Aqueous zinc (Zn) metal batteries have considerable potential as large‐scale energy storage systems. However, cathodic metal ions dissolution and anodic dendrite growth constrain their further development. Here, an ion gradient separator is proposed to stabilize the bi‐electrodes of Zn metal batteries. The results show that the constructed low Zn 2+ concentration region in the separator helps the NH 4 V 4 O 10 (NVO) model cathode to maintain good electrolyte wettability and form a N/ZnS/ZnF 2 ‐rich cathode‐electrolyte interphase (CEI), exhibiting a low vanadium (V) dissolution behavior. Meanwhile, the high Zn 2+ concentration region in the separator and the flexible solid electrolyte interphase (SEI) inhibit the dendrite growth and parasitic reactions of the Zn metal anode and further prevent the diffusion of V ions. As a proof‐of‐concept, the NVO||Zn battery with gradient separator can achieve 88.1% capacity retention even after cycling over 800 cycles at 1 A g −1 , while the ordinary separator only maintains 14.8%. This work presents an innovative gradient separator strategy for achieving high‐performance Zn metal batteries and sheds light on other rechargeable batteries.