Molybdenum oxides (MoO_y) exhibit quite interesting structural, chemical, electrical, optical and electrochemical properties, which are often dependent on the synthetic procedures and fabrication conditions. The MoO_y materiails are promising in numerous current and emerging technological applications, which include nanoelectronics, optoelectronics, energy storage and micromechanics. However, fundamental understanding of the crystal structure and engineering the phase and microstructure is the key to achieving the desired properties and performance in all of these applications. Therefore, in this review, an attempt made to provide a comprehensive review by considering the illustrative examples to highlight the fundamental scientific issues, challenges, and opportunities as related to various Mo-oxides applicable to electrochemical energy applications. In the course of development of lithium batteries delivering high-power and high-energy density for powering electric vehicles, here in this paper, we examine the performances of Mo-oxides, which are candidates as electrodes materials primarily for lithium-ion batteries (LIBs), while some aspects considered in sodium-ion batteries (SIBs) or electrochemical supercapacitors (ECs). Due to the wide range of oxidation states (from +6 to +2) they are promising as both positive (cathode) and negative (anode) electrodes of electrochemical cells. Based on their specific structural, chemical, electrical, and optical properties, which are dependent on the growth conditions and the fabrication technique, this review highlights the progress made in improving and understanding the electrochemical performance of MoO_y compounds. Various materials (2.0 ≤ y ≤ 3.0) including anhydrous, hydrates, nanorods, nanobelts, composites and thin films of MoO_y are considered. Due to their higher oxidation states, MoO_y compounds undergo reversible topotactic lithium intercalation reactions; however, electrochemical features appear strongly dependent on the crystal quality and structural arrangement in the host lattice. Using in-situ and ex-situ X-ray diffraction and Raman spectroscopic data, structural characteristics of various MoO_y are discussed. While the reasons for first-cycle irreversible capacity losses identified and discussed elaborately, the approaches adopted for enhanced performance and/or improvements also summarized. Several sub-stoichiometric MoO_y positive electrodes exhibit excellent cycle life (up to 300 cycles) with high initial coulombic efficiency (80–90%) and large reversible capacity (>300 mAh g⁻¹). Molybdenum oxides also categorized as one of the conversion-type transition-metal oxides and applied as negative electrodes for LIBs and SIBs with a specific capacity approaching 1000 mAh g⁻¹. In addition to the discussion of the key aspects of crystal growth, characterization, and structure-property relationships, the future prospects to design Mo-oxide materials to enhance the structural stability and electrochemical performance are presented and discussed.

氧化钼 (MoO _y ) 表现出非常有趣的结构、化学、电学、光学和电化学特性，这些特性通常取决于合成程序和制造条件。MoO _y材料在众多当前和新兴技术应用中具有前景，包括纳米电子学、光电子学、能量存储和微机械学。然而，对晶体结构的基本理解以及对相和微观结构的设计是在所有这些应用中实现所需特性和性能的关键。因此，在本次审查中，试图通过考虑说明性示例来提供全面审查，以突出与适用于电化学能源应用的各种 Mo 氧化物相关的基本科学问题、挑战和机遇。在为电动汽车提供高功率和高能量密度的锂电池开发过程中，在本文中，我们研究了钼氧化物的性能，它们是主要用于锂离子电池 (LIB) 的电极材料的候选材料，而钠离子电池 (SIB) 或电化学超级电容器 (EC) 中的某些方面也被考虑在内。由于氧化态的范围很广（从 +6 到 +2），它们有望作为电化学电池的正（阴极）和负（阳极）电极。基于它们特定的结构、化学、电学和光学特性，这些特性取决于生长条件和制造技术，本综述重点介绍了在改善和理解 MoO电化学性能方面取得的进展 由于氧化态的范围很广（从 +6 到 +2），它们有望作为电化学电池的正（阴极）和负（阳极）电极。基于它们特定的结构、化学、电学和光学特性，这些特性取决于生长条件和制造技术，本综述重点介绍了在改善和理解 MoO电化学性能方面取得的进展 由于氧化态的范围很广（从 +6 到 +2），它们有望作为电化学电池的正（阴极）和负（阳极）电极。基于它们特定的结构、化学、电学和光学特性，这些特性取决于生长条件和制造技术，本综述重点介绍了在改善和理解 MoO电化学性能方面取得的进展_y化合物。考虑了各种材料（2.0 ≤ y ≤ 3.0），包括无水材料、水合物、纳米棒、纳米带、复合材料和 MoO _y薄膜。由于其较高的氧化态，MoO _y化合物经历可逆的拓扑锂嵌入反应；然而，电化学特征似乎强烈依赖于主晶格中的晶体质量和结构排列。利用原位和异位X 射线衍射和拉曼光谱数据，各种 MoO _{y 的}结构特征进行了讨论。虽然第一次循环不可逆容量损失的原因已经确定和详细讨论，但也总结了为提高性能和/或改进而采用的方法。几种亚化学计量的 MoO _y正极表现出优异的循环寿命（高达 300 次循环）、高初始库仑效率（80-90%）和大可逆容量（>300 mAh g ^-1）。钼氧化物也被归类为转换型过渡金属氧化物之一，并用作 LIB 和 SIB 的负极，比容量接近 1000 mAh g ^-1. 除了讨论晶体生长、表征和结构-性能关系的关键方面之外，还介绍和讨论了设计 Mo 氧化物材料以提高结构稳定性和电化学性能的未来前景。