Revitalizing Dead Zinc with Ferrocene/Ferrocenium Redox Chemistry for Deep‐Cycle Zinc Metal Batteries

Abstract Aqueous zinc (Zn) batteries are highly desirable for sustainable and large‐scale electrochemical energy storage technologies. However, the ceaseless dendrite growth and the derived dead Zn are principally responsible for the capacity decay and insufficient lifespan. Here, we propose a dissolved oxygen‐initiated revitalization strategy to reactivate dead Zn via ferrocene redox chemistry, which can be realized by incorporating a trace amount of poly(ethylene glycol) as a solubilizer to improve the solubility of water‐insoluble ferrocene derivatives. Ferrocene scaffold can be spontaneously oxidized to ferricenium cations by dissolved oxygen, which eradicates the dissolved oxygen‐involved Zn corrosion and insulating by‐product generation. Subsequently, the generated ferricenium cations as the scavenger can rejuvenate electrically isolated dead Zn into electroactive Zn 2+ ions to compensate the zinc loss. Through this design, the symmetric cell exhibited improved cycle life of 3700 h at 10 mA cm −2 , and 220 h under a high depth of discharge of 80 %. Importantly, the Zn||NaV 3 O 8 ⋅ 1.5H 2 O full cells demonstrated the impressive cycling stability over 1500 cycles at a low N/P ratio of 3.0. This work presents an innovative solution for the revitalization of dead Zn to extend the lifespan of deep‐cycling metal batteries.