Akademik Veri Yönetim Sistemi
JOURNAL OF ENERGY STORAGE, cilt.153, ss.120894-120902, 2026 (SCI-Expanded, Scopus)
The development of high-performance aqueous ammonium-ion batteries (AAIBs) requires a deeper understanding of how a material's crystal phase and morphology govern its charge storage. This study decouples this interplay in WO3, engineering distinct polymorphs through controlled synthesis. Through precise hydrothermal synthesis and quantitative Rietveld analysis, we engineered distinct WO3 polymorphs, revealing that a monoclinic-dominant phase (86.4% monoclinic, 13.6% hexagonal) delivers superior performance over other crystal structures. The optimal performance of this monoclinic-dominant WO3 was achieved in a 2 M (NH4)2SO4 electrolyte, yielding a specific capacity of ~60 mAh/g and exceptional long-term stability with 96% capacity retention over 300 cycles. In a WO3//graphite full-cell configuration, this material enabled an impressive energy density of 32.5 Wh/kg and a power density of 238 W/kg. The superior kinetics of the monoclinic phase were quantitatively confirmed by its high NH4+ diffusion coefficient, with values of 2.49 × 10−9 cm2 s−1 (anodic) and 2.10 × 10−9 cm2 s−1 (cathodic), significantly outperforming the mixed-phase and hexagonal-rich samples. Furthermore, ex-situ FTIR analysis provided direct evidence of the NH4+ intercalation process, revealing characteristic N
H bonding vibrations within the WO3 host. Complementary X-ray photoelectron spectroscopy (XPS) further confirmed NH4+ intercalation at the chemical-state level, revealing the emergence of N 1s signals associated with hydrogen-bonded ammonium species and a reversible W6+/W5+ redox transition that provides Faradaic charge compensation during cycling. This work definitively establishes the monoclinic phase as the optimal host for NH4+ storage. It provides a critical design principle: long-term cyclability hinges more on structural integrity than on theoretical kinetics alone.