二硒化钼是一种二维过渡金属硫族化合物材料,凭借其具有较快的离子迁移率、较弱的范德华力的层状结构,在锂离子电池的应用研究中吸引了广泛的关注。同时在镁离子电池应用中表现出潜在的研究前景。然而,有关二硒化钼在锂离子电池中的报道多集中在如何提高储锂性能上,对其离子存储机理缺乏深入研究。此外,在储镁性能和机理上均没有报道。本项工作通过湿化学和高温煅烧两步法合成了二硒化钼纳米球,当二硒化钼纳米球用作锂离子电池负极材料时,在5 A·g^-1的电流密度下展示了高于100 mAh·g^-1的优异高倍率容量;同时,作为镁离子电池正极材料时,在20 mA·g^-1的电流密度下表现出了120 mAh·g^-1的高储镁可逆容量。另外,通过电化学、原位和非原位X射线衍射表征技术,分别揭示了二硒化钼纳米球低平台发生的转化式和高平台发生的类锂硒电池反应并存的储锂机理,以及赝电容式为主,嵌入式为辅的储镁机理。本项工作不仅为二维过渡金属硫族化合物材料的储锂机理提供了深刻的理解,同时也为新型层状储能材料的设计开发提供了方向。

Molybdenum diselenide (MoSe₂) is a two-dimensional (2D) transition metal dichalcogenide (TMD) material, attracting wide attention in lithium ion battery (LIB) and exhibiting great potential in next-generation magnesium ion battery (MIB) due to its unique layered structure with fast ion mobility and weak van der Waals interlayer interaction. However, the reported literatures related to MoSe₂ mainly focus on the enhancement of performance in LIB without deep storage mechanisms investigations. Meanwhile,the magnesium storage capacity and mechanisms have not been explored. In this work, MoSe₂ nanospheres were synthesized via wet chemical route and followed by annealing treatment. When used as the anode and cathode materials, the MoSe₂ nanospheres exhibited the excellent high-rate capacity of > 100 mAh·g^-1 at 5 A·g^-1 for LIB and the excellent reversible discharge capacity of 120 mAh·g^-1 at 20 mA·g^-1 for MIB, respectively. Furthermore, the conversion-type at low plateau and the lithium-selenium battery reaction-type at high plateau of Li⁺ storage mechanisms, as well as the pseudocapacitive reaction as the main and intercalation-type reaction as the supplement storage mechanisms of Mg²⁺ are discussed by electrochemical, in situ and ex situ X-ray diffraction characterizations. This work not only provides the deep understanding of lithium storage mechanism, but also demonstrates the good magnesium storage potential of TMD materials.