Electrochemical Responsive Alginate Chains Rendered Sol‐to‐Gel Gradient Electrolyte towards Practical Ah‐level Zinc Metal Pouch Cell

Abstract Zinc metal batteries have been considered as an appealing candidate for grid‐scale energy storage devices, but are hindered by the instable interface. Herein, we design a sol‐to‐gel gradient electrolyte through the simultaneous electrochemical deposition of Zn 2+ and alginate. The electrochemical gelation of alginate creates a gradient sol‐to‐gel interface and enables the high ionic conductivity, where vehicular mechanism dominated transport is maintained in the bulk electrolyte, while a lean‐water hydrogel like state is created at the Zn/electrolyte interface to reduce water activity. The electrochemical active alginate undergoes a gelation process to form an egg‐shell to confine the Zn 2+ , rendering a 2D growth mode and inhibiting dendrite growth. By taking the advantages of both fast ion transport and stable interface, the full cell based on Zn/VO 2 achieved a stable cycling of 400 cycles at an industrial‐level areal capacity of over 4 mAh cm −2 with a capacity retention of 89.25 %. Additionally, we demonstrate the Ah‐level pouch cell, which stably operates for over 200 cycles with an almost unity average coulombic efficiency (over 99.90 %). By demonstrating the remarkable performance, our work represents an advancement in zinc metal batteries toward a practical scale and is expected to set a stepping stone for transformative advancements in energy storage technologies.