Helmholtz Plane Engineering Enables Dendrite-Free and Subzero-Stable Aqueous Zn Batteries

The practical deployment of aqueous zinc-ion batteries (AZIBs) is hindered by uncontrolled zinc dendrite growth and poor low-temperature performance. Here, we introduce methanol (MeOH), whose dipole moment difference between the hydroxyl and methyl groups enables regulation of the anode-electrolyte interfacial chemistry by reconstructing the Helmholtz plane, thereby achieving stable AZIBs operation. MeOH modulates the Zn2+ solvation structure through competitive coordination with water, which reduces water polarization, enhances electrolyte stability, and increases entropy to increase low-temperature performance. In addition, selective adsorption and spatial hindrance by MeOH promote Zn deposition along the (002) plane, yielding compact and uniform morphologies. As a result, symmetric cells operate stably for more than 1,600 h at 1 mA cm–2 at room temperature and maintain stability for 588 h at −30 °C. Furthermore, Zn||H2V3O8/rGO full cells exhibit 93.5% capacity retention after 3,000 cycles at −30 °C, highlighting exceptional cycling durability under subzero conditions.