Eco‐Friendly Synthesis of Porous Mn 3 O 4 Nanoparticles via Molten Sugar Mediation for Long‐Life Zinc‐Ion Battery Performance

Aqueous rechargeable zinc‐ion batteries (ARZIBs) are promising for sustainable energy storage owing to their safety, low cost, and environmental friendliness. However, high‐performance cathodes face challenges from poor electrical conductivity and structural instability. Here, we report an environmentally benign synthesis of porous Mn 3 O 4 nanoparticles (NPs) via soft templating for ARZIB cathodes. Structural and morphological analyses (FTIR, Raman, FE‐SEM, TEM, XRD, and XPS) confirmed phase‐pure tetragonal Mn 3 O 4 NPs (∼74 nm) with porous, foam‐like morphology, unlike large agglomerated Mn 2 O 3 NPs (∼865 nm) without sugar. XPS spectra confirmed the presence of mixed Mn 2+ and Mn 3+ states in the Mn 3 O 4 sample, which appear to support more reversible Zn 2+ intercalation compared with the predominantly Mn 3+ character of Mn 2 O 3 . Cyclic voltammetry revealed diffusion‐controlled and pseudocapacitive behavior. Unlike Mn 2 O 3 , the Mn 3 O 4 electrode exhibited markedly improved redox activity and faster ion diffusion, which we attribute to its highly porous morphology and the presence of mixed Mn 2+ /Mn 3+ oxidation states. Electrochemical tests in CR2032 coin cells showed a high discharge capacity of 259.46 mA h g −1 at 0.1 A g −1 , excellent rate capability (97.59%), and stable cycling (69.06% retention after 1000 cycles). The synergistic combination of high surface area, mixed‐valence states, and optimized morphology underpins the superior electrochemical performance, offering a scalable and eco‐friendly route toward high‐capacity Mn 3 O 4 cathodes for next‐generation ARZIBs.