Vanadium-doped hexagonal molybdenum trioxide (h-MoO₃) has been systematically investigated as a cathode material for aluminium-ion batteries (AIBs). The evolution of the structural, morphological, compositional, optical, and electrochemical properties of h-MoO₃ doped with different vanadium concentrations were analysed by X-ray diffraction (XRD), micro-Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), high resolution transmission microscopy (HRTEM), SEM and TEM-energy-dispersive X-ray microanalysis (EDS), X-ray photoelectron spectroscopy (XPS), UV-Vis optical absorption and electrochemical techniques. Moderate vanadium doping maintains the hexagonal structure of the oxide host and does not adversely affect the crystallinity of the samples, while inducing morphological changes and local lattice distortions. Optical measurements revealed a significant reduction in the band gap by increasing the dopant concentration, suggesting enhanced electronic conductivity. Electrochemical studies demonstrated that vanadium incorporation improves charge transfer kinetics and cycling stability, with an optimal doping level corresponding to a V/Mo atomic ratio of 0.16, yielding a high specific capacity of ∼240 mA h g⁻¹ at 100 mA g⁻¹ over 100 cycles. However, an excessive vanadium content led to secondary phase formation, structural degradation, non-homogeneous dopant spatial distribution, and decreased electrochemical performance. Ex-situ SEM-EDS and Raman analysis confirmed the excellent structural stability of vanadium-doped h-MoO₃ upon cycling, with uniform chloroaluminate species intercalation. These findings establish vanadium doping as an effective strategy to enhance h-MoO₃ for AIB applications, providing a balance between enhanced conductivity, electrochemical stability, and structural integrity.

中文翻译：

---

钒掺杂六方 MoO3：铝离子电池应用的结构和电化学表征

钒掺杂六方三氧化钼 （h-MoO ₃ ） 作为铝离子电池 （AIB） 的正极材料已被系统研究。 ₃ 通过 X 射线衍射 （XRD）、微拉曼光谱、傅里叶变换红外光谱 （FTIR）、扫描电子显微镜 （SEM）、高分辨率透射显微镜 （HRTEM）、SEM 和 TEM 能量色散 X 射线微分析（EDS）、X 射线光电子能谱 （XPS）、紫外-可见光吸收和电化学技术。适度的钒掺杂保持了氧化物主体的六边形结构，不会对样品的结晶度产生不利影响，同时会引起形态变化和局部晶格畸变。光学测量显示，通过增加掺杂剂浓度，带隙显着降低，表明电子电导率增强。电化学研究表明，钒掺入改善了电荷转移动力学和循环稳定性，最佳掺杂水平对应于 0.16 的 V/Mo 原子比，在 100 次循环中，在 100 mA g⁻¹ 下产生 ∼240 mA h g⁻¹ 的高比容量。然而，过量的钒含量会导致二相形成、结构降解、掺杂剂空间分布不均匀和电化学性能下降。非原位 SEM-EDS 和拉曼分析证实了钒掺杂 h-MoO ₃ 在循环过程中具有出色的结构稳定性，具有均匀的氯铝酸盐物种嵌入。 这些发现确定了钒掺杂是增强 AIB 应用 h-MoO ₃ 的有效策略，在增强的电导率、电化学稳定性和结构完整性之间提供了平衡。