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

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 Zn²⁺ 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 Zn²⁺, 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/VO₂ 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.