Shimoda Keiji, Koganei Kazuto, Takeuchi Tomonari, Matsunaga Toshiyuki, Murakami Miwa, Sakaebe Hikari, Kobayashi Hironori, Matsubara Eiichiro
Office of Society-Academia Collaboration for Innovation, Kyoto University Gokasho Uji Kyoto 611-0011 Japan
National Institute of Advanced Industrial Science and Technology Ikeda Osaka 563-8577 Japan.
RSC Adv. 2019 Aug 5;9(41):23979-23985. doi: 10.1039/c9ra04338a. eCollection 2019 Jul 29.
Vanadium sulfide (VS) is one of the promising positive electrode materials for next-generation rechargeable lithium-ion batteries because of its high theoretical capacity (1196 mA h g). Crystalline VS has a unique structure, in which the Peierls-distorted one-dimensional chains of V-V bonds along the axis are loosely connected to each other through van der Waals interactions. In this study, an amorphous VS is prepared by mechanical milling of the crystalline material, and its lithiation/delithiation behavior is investigated by solid-state nuclear magnetic resonance (NMR) spectroscopy. The amorphous VS shows a chain structure similar to that of crystalline VS. The amorphous host structure is found to change drastically during the lithiation process to form LiVS: the V ions become tetrahedrally coordinated by S ions, in which the valence states of V and S ions simultaneously change from V to V and S to S, respectively. When the Li insertion proceeds further, the valence state of V ions is reduced. After the 1 cycle, the amorphous VS recovers to the chain-like structure although it is highly disordered. No conversion to elemental V is observed, and a high capacity of 700 mA h g is reversibly delivered between 1.5 and 2.6 V.
硫化钒（VS）因其高理论容量（1196 mA h g）而成为下一代可充电锂离子电池颇具前景的正极材料之一。晶体VS具有独特的结构，其中沿 轴的V-V键的佩尔斯畸变一维链通过范德华相互作用彼此松散连接。在本研究中，通过对晶体材料进行机械研磨制备了非晶态VS，并通过固态核磁共振（NMR）光谱研究了其锂化/脱锂行为。非晶态VS呈现出与晶体VS相似的链状结构。发现非晶态主体结构在锂化过程中发生了剧烈变化，形成了LiVS：V离子由S离子进行四面体配位，其中V和S离子的价态分别同时从V变为V和从S变为S。当锂插入进一步进行时，V离子的价态降低。经过1次循环后，尽管非晶态VS高度无序，但它恢复到链状结构。未观察到向元素V的转变，并且在1.5至2.6 V之间可逆地提供了700 mA h g的高容量。
