Reconstruction of Electric Double Layer for Long-Life Aqueous Zinc Metal Batteries

Aqueous rechargeable Zn metal batteries (AZMBs) have attracted widespread attention due to their intrinsic high volumetric capacity and low cost. However, the unstable Zn/electrolyte interface causes Zn dendrite growth and side reactions, resulting in poor Coulombic efficiency and unsatisfactory lifespan. Herein, a SiO2 reinforced-sodium alginate (SA) hybrid film is designed to regulate solid-liquid interaction energy and spatial distribution of all species in the electric double layer (EDL) near the Zn electrode. The unique interfacial layer gives rise to a uniform distribution of Zn2+ in the Helmholtz layer through solvation sheath modulation. Moreover, theoretical calculations show that the SO42- anions and free-water are substantially reduced in the Helmholtz layer, effectively suppressing hydrogen evolution reaction and formation of by-products through strong charge repulsion and hydrogen bond fixing of free-water. The reconfigured EDL not only ensures homogenous and fast Zn2+ transport kinetics for dendrite-free Zn deposition, but also eliminates interface parasitic side reactions. The Zn@SiO2-SA electrode enables excellent cycling stability of symmetrical cells and high-loading full AZMBs with a lifespan over 3000 h and an areal capacity of 2.05 mAh cm(-2), thus laying a solid basis for realizing practical AZMBs.