A Multifunctional Crosslinked F‐Free Binder for MnO₂ Microparticle Thick Cathode in Aqueous Zinc‐Ion Batteries

Abstract In pursuit of a carbon‐neutral society, extensive research has been conducted on Zn‐MnO₂ batteries for their application in energy storage systems. Most efforts have focused on enhancing active material performance at the lab scale, with less attention on high‐loaded electrodes incorporating micro‐sized MnO₂ for practical application. Although thick electrodes are required to improve the energy density of cells, unwanted issues such as poor wettability, Mn²⁺ dissolution, and low adhesion of the electrodes should be addressed to activate these high‐loaded electrodes. To overcome these problems, a multifunctional F‐free hydrophilic crosslinked (HPC) binder is proposed. Unlike F‐containing polyvinylidene fluoride and non‐crosslinked HPC binders showing weak adhesion and binder dissolution, respectively, the HPC binder exhibits hydrophilic, physically stable, and environmentally friendly natures. Moreover, due to the presence of carboxylate groups showing strong adsorption to eluted Mn²⁺ ions, the Mn²⁺ migration to the anode side is largely suppressed. Benefiting from these interesting features, the HPC cell exhibits stable cell operation by minimizing the accumulation of irreversible Zn‐vernadite, owing to maintaining the electrode integrity at a practical level of 13.3 mg cm⁻². This study highlights the importance of binder design, enabling the use of thick electrodes as a step toward the commercialization of Zn–MnO₂ batteries.