Lithium-sulfur battery is made of sulfur as the cathode material, lithium metal plate as the anode of the secondary battery, the theoretical specific capacity and higher than the theoretical energy of the battery, respectively, 1672mAh · g-1 and 2600Wh · kg-1, is considered now The most research value and application prospects of high-energy lithium secondary battery system. However, there are still many problems to be solved in current lithium-sulfur batteries, such as low cycle life, low active material utilization, poor conductivity of the sulfur cathode material and its discharge products, and the like.
Recently, the Chinese University of Science and Technology Qian Yitai, Zhu Yongchun task force developed a new lithium-sulfur battery cathode material - selenium and sulfur solid solution. Based on the binary phase diagrams of the two commercially available sulfur powders and selenium powders, the researchers synthesized the porous carbons prepared in advance from the experimental group to obtain sulfur-rich S1-xSex / C (x ≈0.1 , 0.08, 0.06, 0.05) complex. The results show that the prepared S1-xSex / C composites still show excellent cycle stability and rate performance in the carbonate electrolyte: 500 cycles at a current density of 0.5 A g-1, the specific capacity remains at 1105 mA h g-1; specific capacity of 617 mA h g-1, even at high current densities of 20 A g-1. By liquid-phase Raman and X-ray photoelectron spectroscopy, it was found that S1-xSex / C composites have stable selenium-sulfur bond both before and after circulation. This research not only reveals the stable mechanism of selenium and sulfur solid solution, but also paves the way for further research to develop other new cathode materials for lithium-sulfur batteries. A related research paper was published in Energy Environ. Sci., 2015, DOI: 10.1039 / C5EE01470K and was selected as an inset for the journal No. 11, 2015. The thesis mainly completes the postdoctoral researchers Li Xiaona and Liang Jianwen who are the subject group.
On the other hand, sulfur and the same family of selenium cathode material has also drawn much attention in recent years. The group developed a new salt q method to selenium poured into the porous carbon, to avoid the inert gas or vacuum atmosphere protection, to some extent avoid the temperature fluctuations in the heating process, which will help pour the molten selenium into In porous carbon, the proportion of active Se in Se / C composite was increased from 36 54% reported in the past to 72%. The prepared Se / C composites showed excellent lithium storage properties: 1000 cycles at 1 C, with a capacity retention of 95.7%. Se / C composites still showed better cycling stability in Na-Se battery test. The salt q method proposed by the research group not only can be used as a universal method to infuse other low melting point materials into the porous carbon base material, but also is simple and easy to be carried out to enlarge the production. It is expected to promote the Li-Se, Na- Se and other related batteries for further development. Relevant results recently published in the "advanced functional materials," and was Wiley's "Materials View China" as the highlight of the study reported. The first author is the postdoctoral researcher Li Xiaona.
In addition, the group also developed the ice-bath method to prepare graphene-coated selenium / polyaniline core-shell nanowires with excellent properties. For the first time, the idea of ​​melting Se into porous carbon was broken for the first time. Graphene The combination of the high conductivity, the unique conductive polyaniline shell and the selenium nanowire one-dimensional structure make the composite exhibit good electrochemical performance. Relevant results have been published in "Nano Energy" (Nano energy 2015, 13, 592 600). The first author of the paper is Dr. Zhang Jingjing.
The above work has been funded by the National Natural Science Foundation.
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