Multivariate Optimization of Easily Prepared Indium Substrates for Mild‐Acid Zinc‐Ion Batteries

The commercialization of aqueous zinc‐ion batteries (ZIBs) remains hindered by poor Zn electrodeposition efficiency in mild‐acidic electrolytes, mainly due to the parasitic hydrogen evolution reaction (HER). The use of metallic substrates, such as copper or indium, has proven to be one of the most effective and potentially industrially viable strategies for kinetically promoting zinc electrodeposition over hydrogen evolution, while simultaneously ensuring a uniform deposit morphology. Here, a scalable strategy to fabricate indium‐containing substrates via galvanic displacement, offering a simple, cost‐effective, and environmentally sustainable alternative to conventional production methods has been presented. The prepared substrates demonstrate average efficiencies exceeding 99% over 150 Zn stripping/plating cycles at a realistic depth of discharge, requiring a fraction of Zn reservoir compared to standard Zn electrodes. A multivariate design of experiment (DOE) approach is employed to optimize both electrode fabrication and electrolyte parameters, highlighting key variables affecting Zn deposition efficiency and uncovering critical synergistic and antagonistic effects otherwise hidden in traditional one‐variable‐at‐a‐time (OVAT) methods. Overall, this work not only demonstrates the feasibility of upscaling indium‐modified substrates for high‐performance ZIBs but also emphasizes the power of DOE in accelerating material optimization and deepening the understanding of complex electrochemical systems.