Three‐in‐One: Integrating Polymer Dots and δ‐MnO ₂ for Powerful Zn‐Mn Batteries

ABSTRACT δ‐MnO 2 is a promising cathode material for aqueous zinc batteries (AZBs) due to its large interlayer spacing and multi‐ion intercalation capability. However, its practical performance is hampered by some non‐negligible inherent drawbacks such as the scarcity of ion‐insertion facets and blockage by associated byproducts, namely zinc hydroxide sulfates (ZHS). In this study, we coat δ‐MnO 2 with polymer dots (PDs) bearing diverse amino functional groups to realize a synergistic “three‐in‐one” effect: selective exposure of ion‐insertion planes through oriented recrystallization, formation of filter‐splitter‐shield (FSS) layer for hydrated‐cation transport, and robust adhesion for cathode construction. Spectroscopic analyses combined with molecular dynamics simulations confirm that the alkaline microenvironment generated by the PDs directs the δ‐MnO 2 toward oriented recrystallization, thereby unveiling additional ion‐entry sites. In situ characterizations further demonstrate that the PDs functioning as the FSS layer can effectively promote the dissociation of water into H 3 O + and OH − . This process facilitates cation transport via the amino sites, inhibits the aggregation of ZHS, and maintains the structural stability of δ‐MnO 2 . Consequently, the optimized PDs‐MnO 2 cathode achieves a high specific capacity of 274 mAh g −1 and retains 97.3% of its initial capacity after 5000 cycles, highlighting the efficacy of the PDs‐derived coating layer in δ‐MnO 2 cathodes.