Calcium Alginate Hydrogel Coating Comprehensively Optimizes Zn Deposition Behavior of Aqueous Zinc-Ion Batteries Anode

Aqueous zinc-ion batteries (AZIBs) with Zn metal as the anode have great potential for large-scale energy storage due to their unique advantages. However, Zn anodes face unfavorable conditions such as the hydrogen evolution reaction (HER) and dendrite growth, which limit the practical application of AZIBs. We constructed a calcium alginate (CA) hydrogel protective layer on the Zn foil surface. The carboxyl and hydroxyl groups in the CA hydrogel can form hydrogen bonds with H2O and inhibit the HER. Meanwhile, the CA coating also promotes the desolvation process of Zn(H2O)62+, which results in uniform dispersion of Zn2+ flux. The CA coating can homogenize the electric field distribution on the anode surface and inhibit the growth of dendrites. Therefore, the CA-Zn symmetric batteries can be stably cycled for 2200 h at 0.5 mA cm–2, showing excellent cycling performance. Overall, the introduction of a CA hydrogel protective layer effectively optimized the unfavorable conditions faced by the Zn anode.