ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Recently two-dimensional layered transition metal dichalcogenides (TMDs) have attracted great scientific interest in electrochemical energy storage. As an important family member of TMDs, vanadium disulfide (VS2) is a promising electrode material for lithium-ion cells because of its remarkable electrical conductivity and fast Li + diffusion rate, but its electrochemical reaction mechanism is still poorly understood. Herein, we have prepared an electrode consisting of VS2 nanosheets and systematically investigated its structural and chemical evolution during the electrochemical processes by employing both in situ and ex situ X-ray spectroscopies. The VS2 undergoes intercalation and conversion reactions in sequence during discharge and this process is found to be partially reversible during the subsequent charge. The decreased reversibility of the conversion reaction over extended cycles could be mainly responsible for the capacity fading of the VS2 electrode. In addition, the hybridization strength between S and V shows a strong dependence on the states of charge, as directly proved by the intensity change of the V-S hybridized states and pure V states. We also reveal that the solid electrolyte interphase on the electrode surface is dynamically evolved during cycling, which may be a universal phenomenon for conversion-based electrodes. This study is expected to be beneficial for the further development of high-performance VS2based electrodes.
Lithium nitrate (LiNO 3) has been the most studied electrolyte additive in lithium-sulfur (Li-S) cells, due to its known function of suppressing the shuttle effect in Li-S cells, which provides a significant increase in the cell's coulombic efficiency and cycling stability. Previous studies indicated that LiNO 3 participated in the formation of a passive layer on the lithium electrode and thus suppressed the redox shuttle of the dissolved polysulfides. However, the effects of the LiNO 3 on the positive electrode materials have rarely been investigated. By combining scanning electron microscopy (SEM), element-selective X-ray absorption spectroscopy, and electrochemical characterizations, we performed a comprehensive study of how the LiNO 3 altered the properties of the sulfur electrode/electrolyte interface in Li-S cells and thus influenced the cell performance. We found that LiNO 3 is a double-edged sword in the Li-S cell: on one hand, it increased the consumption of the active sulfur; on the other hand, it promoted the survival of the carbon matrix constituent in the sulfur electrode. These two competitive effects indicated that a proper moderate concentration of LiNO 3 is required to achieve an optimized cell performance.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.