In-Built Hybrid SEI with Weak Hydrophilicity from a Hydrogel Electrolyte for Stable Zinc Anodes

Zinc metal anodes have great prospects but encounter challenges, such as dendrites and adverse reactions. A stable solid electrolyte interface (SEI) that not only enhances zinc plating/stripping but also suppresses side reactions is crucial for a highly reversible zinc anode. In this study, a double-network hydrogel electrolyte containing polysaccharide carrageenan with a low level of the lowest unoccupied molecular orbital energy (LUMO) is designed to develop an in-built organic-inorganic hybrid SEI. This hybrid SEI features weak hydrophilicity but low interfacial impedance, which endows zinc anodes with durable anticorrosion properties in the aqueous environment and facilitates uniform Zn²⁺ deposition, thereby boosting the overall cycling stability in both symmetric and asymmetric cells. Consequently, the Zn||MnVO@CNT full cell achieves 81.8% capacity retention for 1000 cycles with a high MnVO@CNT loading of 13.6 mg cm^-2 at 1 A g^-1. Additionally, a pouch cell with a capacity of 22 mAh retained 76.7% over 700 cycles at 1 A g^-1. This work highlights the advantages of hydrogel electrolytes in the construction of in-built SEIs and provides significant insights for the future development of zinc metal batteries.